The University of Western Australia **Etiopathogenesis -2** **Host responses to** **oral biofilms** **Associate Professor Leticia A Miranda*** DDS, Specialist (*Perio*), MSc (*Perio*), PhD (*Perio, Medicine*) **Dr. Pradeep Koppolu*** BDS, MDS (*Perio*), PhD (Malaysia), FICOI, FPFA, PDCR Discipline Lead & Program Convenor Periodontics and Implantology *\*notes* **Etiopathogenesis -2** **Host responses to oral biofilms** **Associate Professor Leticia A Miranda*** DDS, Specialist (*Perio*), MSc (*Perio*), PhD (*Perio, Medicine*) **Dr. Pradeep Koppolu*** BDS, MDS (*Perio*), PhD (Malaysia), FICOI, FPFA, PDCR Discipline Lead & Program Convenor Periodontics and Implantology *\*notes* The University of Western Australia institutional logo located in the top right corner. <details> <summary>Reading Resources</summary> **Reading Resources** **BOOK** *Periodontology at a Glance* Clerehugh, Valerie. ; Tugnait, Aradhna. ; Genco, Robert J. ; Somerset : Wiley; 2013 [Available Online] → <!-- Image (60, 355, 196, 647) --> **Clinical Periodontology and Implant Dentistry, 2 Volume Set** by Niklaus P. Lang, , Jan Lindhe, , and Niklaus P Lang **PUBLISHER** John Wiley & Sons, Incorporated **DATE** 2015-03-25 **NEWMAN AND CARRANZA'S** **CLINICAL PERIODONTOLOGY** **AND IMPLANTOLOGY** 14**th** **EDITION** **CHAPTER 11** **Host-Microbe Interactions and the Inflammatory Response** Keith L. Kirkwood | Carlos Rossa Jr. | George Hajishengallis | Ann Decker | Yvonne L. Hernandez-Kapla </details>     **Reading Resources** **BOOK** *Periodontology at a Glance* Clerehugh, Valerie. ; Tugnait, Aradhna. ; Genco, Robert J. ; Somerset : Wiley; 2013 [Available Online] → **Clinical Periodontology and Implant Dentistry, 2 Volume Set** by Niklaus P. Lang, Jan Lindhe, and Niklaus P Lang **PUBLISHER** John Wiley & Sons, Incorporated **DATE** 2015-03-25 **NEWMAN AND CARRANZA'S CLINICAL PERIODONTOLOGY AND IMPLANTOLOGY 14th EDITION** **CHAPTER 11** **Host-Microbe Interactions and the Inflammatory Response** Keith L. Kirkwood | Carlos Rossa Jr. | George Hajishengallis | Ann Decker | Yvonne L. Hernandez-Kapla Cover image of the book 'Periodontology at a Glance'. The cover features a close-up clinical photograph of teeth with visible redness and inflammation on the gum line, likely illustrating periodontal disease. Small thumbnail image showing the spine or front cover of the book set 'Clinical Periodontology and Implant Dentistry'. Front cover of the textbook 'Newman and Carranza's Clinical Periodontology and Implantology', 14th Edition. The cover displays the title in large white text against a blue gradient background. Title page for Chapter 11: Host-Microbe Interactions and the Inflammatory Response from the textbook Newman and Carranza's Clinical Periodontology and Implantology. It lists the authors Keith L. Kirkwood, Carlos Rossa Jr., George Hajishengallis, Ann Decker, and Yvonne L. Hernandez-Kapla. **The University of Western Australia** ## Learning outcomes **Recognize periodontal health and disease;** **Understand the peculiarities of the periodontal niche;** **Identify the key components of the host response in the dento- gingival area;** **Understand the histopathology of periodontal diseases.** Learning outcomes - **Recognize periodontal health and disease;** - **Understand the peculiarities of the periodontal niche;** - **Identify the key components of the host response in the dento-gingival area;** - **Understand the histopathology of periodontal diseases.** The official logo of The University of Western Australia, featuring a shield with an open book and a swan. # Periodontium  Periodontium Anatomical cross-section diagram of the periodontium. The image illustrates a tooth structure (left) with surrounding soft tissue (right). Key labeled components include: Cementum, Periodontal ligament, and Alveolar bone on the left side pointing to hard tissues; Gingival sulcus, Gingival margin, Free gingiva, Free gingival groove, Attached gingiva, Mucogingival junction, and Alveolar mucosa on the right side pointing to soft tissue regions. # Periodontal health and diseases    Periodontal health and diseases Clinical photo showing a healthy mouth with pink, firm gingiva and no visible inflammation or recession. Clinical photo showing gingival recession (indicated by black arrow) exposing the root surface of the central incisor. Clinical photo showing advanced periodontal disease with significant tooth mobility (indicated by black arrow), bone loss, and generalized gingival recession.     Clinical photo showing a close-up view of anterior teeth with dental floss being used to clean the interproximal spaces. The gingiva appears slightly inflamed. Clinical photo displaying a full frontal view of the upper and lower anterior teeth. The teeth appear relatively aligned with healthy-looking gingival tissue. A watermark for 'THE UNIVERSITY OF WESTERN' is visible in the top right corner. Clinical photo showing an occlusal view of the upper and lower anterior teeth. The teeth are well-aligned with good contact points between them. Clinical photo showing a close-up view of the posterior teeth (premolars and molars) with significant malocclusion. The teeth are crowded and misaligned, with some appearing rotated or overlapping. THE UNIVERSITY OF WESTERN AUSTRALIA   THE UNIVERSITY OF WESTERN AUSTRALIA Clinical photograph showing the anterior maxillary dentition with a periodontal probe inserted between the central incisors to measure gingival crevicular depth. The image displays gingival inflammation and recession. Periapical radiograph of the maxillary anterior teeth showing root morphology and periapical bone levels. **Periodontal area peculiarities** **Biofilms always present** Health Disease Intact enamel Supragingival eubiotic biofilm Gingival crevice Subgingival eubiotic biofilm Homeostatic inflammation Intact bone Supragingival dysbiotic biofilm EPS matrix and acidogenic–aciduric environment Periodontitis Periodontal pocket, attachment loss Subgingival dysbiotic communities on root surface, in GCF and in and on the epithelium Severe, destructive inflammation Resorbed bone **Caries** Demineralized enamel leading to cavitation **Eubiotic:** in a healthy balance with the host. **Dysbiotic:** When balance with the host. Is disrupted Supragingival biofilm = Gingivitis Subgingival biofilm = Periodontitis **Periodontitis peculiarities** Tooth: non-shedding surface, partially outside the body (=oral cavity) Bacterial load is located generally “outside” the body Challenge for the immune-inflammatory response to take action Endogenous/opportunistic infection **Dysbiosis** Plaque as a biofilm Hajishengallis et al 2015  **Periodontal area peculiarities** **Biofilms always present** Health Disease - Intact enamel - Supragingival eubiotic biofilm - Gingival crevice - Subgingival eubiotic biofilm - Homeostatic inflammation - Intact bone - Supragingival dysbiotic biofilm - EPS matrix and acidogenic–aciduric environment Periodontitis - Periodontal pocket, attachment loss - Subgingival dysbiotic communities on root surface, in GCF and in and on the epithelium - Severe, destructive inflammation - Resorbed bone **Caries** - Demineralized enamel leading to cavitation **Eubiotic:** in a healthy balance with the host. **Dysbiotic:** When balance with the host is disrupted - Supragingival biofilm = Gingivitis - Subgingival biofilm = Periodontitis **Periodontitis peculiarities** - Tooth: non-shedding surface, partially outside the body (=oral cavity) - Bacterial load is located generally "outside" the body - Challenge for the immune-inflammatory response to take action - Endogenous/opportunistic infection - **Dysbiosis** - Plaque as a biofilm Hajishengallis et al 2015 Labelled diagram illustrating 'Periodontal area peculiarities' comparing a tooth in Health vs. Disease states. The diagram features a central cross-section of a tooth and gingiva divided by a vertical dashed line. Labels on the left (Health) include: Intact enamel, Supragingival eubiotic biofilm, Gingival crevice, Subgingival eubiotic biofilm, Homeostatic inflammation, and Intact bone. Labels on the right (Disease) identify Caries with demineralized enamel, Supragingival dysbiotic biofilm, EPS matrix, Periodontitis with periodontal pocket/attachment loss, subgingival dysbiotic communities, severe destructive inflammation, and resorbed bone. Additional annotations include two cloud shapes on the far left defining 'Eubiotic' (yellow) and 'Dysbiotic' (red). Text at the bottom summarizes that supragingival biofilm equals Gingivitis and subgingival biofilm equals Periodontitis. # Periodontal health and diseases **Dysbiosis** Dysbiosis is any perturbation of the normal microbiome content that could disrupt the symbiotic relationship between the host and associated microbes, a disruption that can result in diseases, such as inflammatory bowel disease and other gastrointestinal (GI) disorders, including gastritis, peptic ulcer disease, irritable bowel syndrome, and even gastric and colon cancer [3–6]. From: **The Microbiota in Gastrointestinal Pathophysiology**, 2017 Kinane, D. F. *et al.* (2017) Periodontal diseases *Nat. Rev. Dis. Primers* doi:10.1038/nrdp.2017.38   **Dysbiosis** Dysbiosis is any perturbation of the normal microbiome content that could disrupt the symbiotic relationship between the host and associated microbes, a disruption that can result in diseases, such as inflammatory bowel disease and other gastrointestinal (GI) disorders, including gastritis, peptic ulcer disease, irritable bowel syndrome, and even gastric and colon cancer [3–6]. From: **The Microbiota in Gastrointestinal Pathophysiology**, 2017 Kinane, D. F. *et al.* (2017) Periodontal diseases *Nat. Rev. Dis. Primers* doi:10.1038/nrdp.2017.38 A flowchart diagram illustrating susceptibility to periodontal diseases. The top node is labeled 'Microbial dysbiosis,' which points downward to a central image of a tooth and gums labeled 'Healthy periodontium.' From this central point, the diagram branches into two pathways representing balance scales. The left pathway shows a scale tipping towards the right (green), leading to an outcome box labeled 'Healthy periodontium' with a corresponding healthy tooth illustration. This side is associated with a green box listing 'Resistance' factors: Genetic factors, Innate immune response, Adaptive immune response, Inflammation, and Other structural components. The right pathway shows a scale tipping towards the left (orange), leading to an outcome box labeled 'Diseased periodontium' with a corresponding illustration showing red inflammation on the gum line. This side is associated with an orange box listing 'Risk factors': Environmental (Smoking, Dental plaque accumulation, Socioeconomic status) and Host-specific (Genetic factors, Overall inflammatory burden). Below the diagram, text states: 'Nature Reviews | Disease Primers' and 'Disease progression depends on the extent and severity of the microbial biofilm challenge (microbial dysbiosis) and the host response, which is influenced by protective factors (resistance) and promoting factors (risk factors).' A citation at the bottom reads: 'Kinane, D. F. et al. (2017) Periodontal diseases Nat. Rev. Dis. Primers doi:10.1038/nrdp.2017.38' A dark grey rectangular text box defining 'Dysbiosis'. The definition states that dysbiosis is any perturbation of the normal microbiome content that could disrupt the symbiotic relationship between the host and associated microbes, potentially resulting in diseases such as inflammatory bowel disease, gastritis, peptic ulcer disease, irritable bowel syndrome, and gastric/colon cancer. It cites 'The Microbiota in Gastrointestinal Pathophysiology, 2017' as the source. # 7 **Host defences** (a) Host defences effective against microbial challenge in a conducive environment for periodontal health **Conducive environment** (b) Reduced or defective host defences are ineffective against normal microbial challenge **Host defences ineffective** Balance upset **Environment NOT conducive to health** (c) Increased microbial challenge overwhelms normal host defences **Host defences** Balance upset **Environment NOT conducive to health** **Key:** * Reduced * Normal * Increased **Health** -> **Disease** **Microbial challenge** **Health** -> **Disease** **Increased microbial challenge** **Figure 7.1 Concept of balance between host defences, microbial challenge and environment.** (a) Balance and periodontal health. (b) Host defences have a defect or are ineffective against microbial challenge, tipping the balance to periodontal destruction. (c) Microbial challenge overwhelms the host defences leading to an upset balance and periodontal destruction - this may relate to the environment not being conducive and/or changes in quality, quantity or virulence of microorganisms.  **Host defences** (a) Host defences effective against microbial challenge in a conducive environment for periodontal health **Conducive environment** (b) Reduced or defective host defences are ineffective against normal microbial challenge **Host defences ineffective** Balance upset **Environment NOT conducive to health** (c) Increased microbial challenge overwhelms normal host defences **Host defences** Balance upset **Environment NOT conducive to health** **Key:** - Reduced - Normal - Increased **Health** -> **Disease** **Microbial challenge** **Health** -> **Disease** **Increased microbial challenge** **Figure 7.1 Concept of balance between host defences, microbial challenge and environment.** (a) Balance and periodontal health. (b) Host defences have a defect or are ineffective against microbial challenge, tipping the balance to periodontal destruction. (c) Microbial challenge overwhelms the host defences leading to an upset balance and periodontal destruction - this may relate to the environment not being conducive and/or changes in quality, quantity or virulence of microorganisms. Labelled diagram illustrating the concept of balance between host defences, microbial challenge, and environment using three distinct panels labeled (a), (b), and (c). The visual uses a seesaw metaphor where weights represent 'Host defences' and 'Microbial challenge'. Panel (a) shows balanced weights with a 'Conducive environment', resulting in 'Health'. Panel (b) shows reduced/ineffective host defences tipping the scale towards disease due to an 'Environment NOT conducive to health'. Panel (c) shows increased microbial challenge overwhelming normal defences, also tipping the scale to 'Disease'. A key at the bottom left defines the weight shapes: pink for Reduced, grey for Normal, and green for Increased. **Current PD etiopathogenesis model** **The University of Western Australia** *Behavourial risk factors absent* *Environmental risk factors absent* *Genetic risk factors absent* *Epipenetic effects not evident* *Behavourial risk factors present* *Environmental risk factors evident* *Genetic risk factors present* *Enzigenetic effects evident* **Clinical Health** **Gingivitis** **Periodontitis** **Health Promoting biofilm =** **Symbiosis** **Incipient Dysbiosis** **(Quorum Sensing Bacteria)** **Frank Dysbiosis** **(Pathogenic Biofilm)** *Low biomass* *High biomass* *High biomass* **Complement** **PMNs** **Proportionate Host response** **Antibody** **PMNs ++** **T & B cells** **Proportionate Host response** **Antibody** **PMNs +++** **Plasma cells** **Acute Resolution of inflammation** **Chronic Resolution of inflammation** **Faled Resolution of inflammation** **Antigens** **Bact'1 DNA** **fMLP** **High biomass** **Antigens** **Virulence Factors** **LPS** **Gingivapinas** **LPS** **Connective Tissue & Zone Damage** **Dis-proportionate Host response** **(hyper-inflammatory)** **DAMPs** **Haem** **GCF** **Chronic non-Resolving inflammation** **Cytokines** **Prostanoids** **MMPs** **Oxidative Stress** **FIGURE 1** Contemporary model of host–microbe interactions in the pathogenesis of periodontitis, in which the host response drives an incipient dysbiosis (gingivitis). If the biofilm is not disrupted/removed, frank dysbiosis results and perpetuates a chronic nonresolving and destructive inflammation. DAMPs, damage-associated molecular patterns; fMLP, N- formylmethionyl- leucyl- phenylalanine; GCF, gingival crevicular fluid; LPS, lipopolysaccharide; MMPs, matrix metalloproteinases; PMNs, polymorphonuclear neutrophils. This figure is referred fromref. 106. Murakami S, Mealey BL, Mariotti A,Chapple ILC. Dental plaque–induced gingival conditions.J C i n Periodontol. 2018;45(Suppl 20):S17–S2  **Current PD etiopathogenesis model** **The University of Western Australia** - Behavourial risk factors absent - Environmental risk factors absent - Genetic risk factors absent - Epipenetic effects not evident - Behavourial risk factors present - Environmental risk factors evident - Genetic risk factors present - Enzigenetic effects evident **Clinical Health** **Gingivitis** **Periodontitis** **Health Promoting biofilm = Symbiosis** **Incipient Dysbiosis (Quorum Sensing Bacteria)** **Frank Dysbiosis (Pathogenic Biofilm)** - Low biomass - High biomass - High biomass **Complement** **PMNs** **Proportionate Host response** **Antibody** **PMNs ++** **T & B cells** **Proportionate Host response** **Antibody** **PMNs +++** **Plasma cells** **Acute Resolution of inflammation** **Chronic Resolution of inflammation** **Faled Resolution of inflammation** **Antigens** **Bact'1 DNA** **fMLP** **High biomass** **Antigens** **Virulence Factors** **LPS** **Gingivapinas** **LPS** **Connective Tissue & Zone Damage** **Dis-proportionate Host response (hyper-inflammatory)** **DAMPs** **Haem** **GCF** **Chronic non-Resolving inflammation** **Cytokines** **Prostanoids** **MMPs** **Oxidative Stress** **FIGURE 1** Contemporary model of host–microbe interactions in the pathogenesis of periodontitis, in which the host response drives an incipient dysbiosis (gingivitis). If the biofilm is not disrupted/removed, frank dysbiosis results and perpetuates a chronic nonresolving and destructive inflammation. DAMPs, damage-associated molecular patterns; fMLP, N- formylmethionyl- leucyl- phenylalanine; GCF, gingival crevicular fluid; LPS, lipopolysaccharide; MMPs, matrix metalloproteinases; PMNs, polymorphonuclear neutrophils. This figure is referred fromref. 106. Murakami S, Mealey BL, Mariotti A,Chapple ILC. Dental plaque–induced gingival conditions.J C i n Periodontol. 2018;45(Suppl 20):S17–S2 Labelled diagram illustrating the 'Current PD etiopathogenesis model' showing three stages: Clinical Health, Gingivitis, and Periodontitis. The diagram depicts the progression from health to disease based on risk factors (behavioural, environmental, genetic) and epigenetic effects. It visualizes changes in biofilm composition (Health Promoting biofilm vs Incipient Dysbiosis vs Frank Dysbiosis), host response type (Proportionate vs Dis-proportionate), and resolution status (Acute vs Chronic/Failed Resolution). Arrows indicate the flow of antigens, virulence factors, and inflammatory mediators like PMNs, Antibodies, Cytokines, and MMPs. **Periodontal microbiota** P. gingivalis B. forsythus T. denticola C. gracilis C. rectus C. showae E. nodatum F. nuc. nucleatum F. nuc. polymorphum P. intermedia P. micros P. nigrescens S. constellatus Actinomyces species V. parvula A. odontolyticus E. corrodens C. gingivalis C. sputigena C. ochracea C. concisus A. actino. a S. mitis S. oralis S. sanguis Streptococcus sp. S. gordonii S. intermedius Periodontal Health Actinomyces other Periodontitis Supragingival Subgingival SOCRANSKY, S.S. and HAFFAJEE, A.D. (2002), Dental biofilms: difficult therapeutic targets. Periodontology 2000, 28: 12-55.   **Periodontal microbiota** - P. gingivalis - B. forsythus - T. denticola - C. gracilis - C. rectus - C. showae - E. nodatum - F. nuc. nucleatum - F. nuc. polymorphum - P. intermedia - P. micros - P. nigrescens - S. constellatus - Actinomyces species - V. parvula - A. odontolyticus - E. corrodens - C. gingivalis - C. sputigena - C. ochracea - C. concisus - A. actino. a - S. mitis - S. oralis - S. sanguis - Streptococcus sp. - S. gordonii - S. intermedius Periodontal Health - Actinomyces - other Periodontitis - Supragingival - Subgingival SOCRANSKY, S.S. and HAFFAJEE, A.D. (2002), Dental biofilms: difficult therapeutic targets. Periodontology 2000, 28: 12-55. A labelled diagram illustrating the ecological succession of periodontal microbiota. A central pyramid structure represents different microbial complexes arranged by color: a blue base layer labeled 'Actinomyces species', a purple section labeled 'V. parvula / A. odontolyticus', a green section labeled with 'E. corrodens', 'C. gingivalis', 'C. sputigena', 'C. ochracea', 'C. concisus', 'A. actino. a', an orange middle section containing 'C. gracilis' through 'S. constellatus', and a red top section labeled 'P. gingivalis', 'B. forsythus', 'T. denticola'. Surrounding callouts list specific bacterial species associated with each colored region. A set of four pie charts comparing microbial group distribution between 'Periodontal Health' and 'Periodontitis' conditions, further divided into 'Supragingival' and 'Subgingival' sites. Each chart displays colored segments representing different microbial groups including 'Actinomyces' and 'other'. Visual comparison shows distinct proportions of these groups across the four categories. Virulence factors – **perio** microbiota Enzymes Waste products **Protein**ases Leukotoxins Lipopolysaccharides **EVADE HOST** RESPONSES <img>Bacterial Biofilm on tooth surface with pellicle  Virulence factors – **perio** microbiota - Enzymes - Waste products - **Protein**ases - Leukotoxins - Lipopolysaccharides **EVADE HOST RESPONSES** Bacterial Biofilm on tooth surface with pellicle Labelled diagram illustrating bacterial biofilm formation on a tooth surface. The image shows bacteria (depicted as pink and purple rod shapes) embedded within a matrix labeled 'Bacterial Biofilm'. This biofilm sits atop a layer labeled 'Pellicle', which is situated above the wavy black lines representing the 'Tooth Surface'. Arrows indicate the progression or interaction between these layers. <table> <tr> <th>Immunity</th> </tr> <tr> <td><table> <tr> <td>Innate Immunity (Immediate response)</td> <td>Adaptive Immunity (Delayed response)</td> </tr> <tr> <td><table> <tr> <td>Barriers</td> <td>Complement system</td> <td>PMNL's Macrophages</td> </tr> </table></td> <td><table> <tr> <td>B cells</td> <td>T cells</td> </tr> </table></td> </tr> </table></td> </tr> </table> Innate immune system Dendritic cell Eosinophil NK cell Basophil Monocyte Neutrophil Mast cell Macrophage Complement protein Common pathway γδ T cell NK T cell Adaptive immune system T cell CD8+ T cell CD4+ T cell B cell Antibodies Cytokines   **Immunity** | Innate Immunity (Immediate response) | Adaptive Immunity (Delayed response) | | :--- | :--- | | Barriers, Complement system, PMNL's, Macrophages | B cells, T cells | **Innate immune system** - Dendritic cell - Eosinophil - NK cell - Basophil - Monocyte - Neutrophil - Mast cell - Macrophage - Complement protein - Common pathway - γδ T cell - NK T cell **Adaptive immune system** - T cell - CD8+ T cell - CD4+ T cell - B cell - Antibodies - Cytokines Hierarchical flowchart illustrating the classification of Immunity. The root node 'Immunity' branches into 'Innate Immunity (Immediate response)' and 'Adaptive Immunity (Delayed response)'. Under Innate Immunity, sub-categories include 'Barriers', 'Complement system', and 'PMNL's Macrophages'. Under Adaptive Immunity, sub-categories are 'B cells' and 'T cells'. All nodes are orange rectangles with black text. Composite diagram comparing the 'Innate immune system' (left panel, pink background) and 'Adaptive immune system' (right panel, green background). The left panel displays illustrations of Dendritic cell, Eosinophil, NK cell, Basophil, Monocyte, Neutrophil, Mast cell, Macrophage, and Complement protein. The right panel shows a T cell branching into CD8+ T cell and CD4+ T cell (which releases Cytokines), a B cell producing Antibodies, and a central 'Common pathway' box containing γδ T cell and NK T cell. ```mermaid graph TD subgraph Innate_Immunity [Innate immunity] Virus --> Interferons Interferons --> Block Some_Bacteria_1[Some Bacteria] --> Defensins Some_Bacteria_1 --> Lysozyme Lysozyme --> Lysis Defensins --> Lysis Injury --> Tissue_damage Some_bacteria_2[Some bacteria] --> Tissue_damage Tissue_damage --> Acute_inflammation Tissue_damage --> Chronic_inflammation Acute_inflammation --> Healing Complement --> Mast_cell Complement --> MAC Complement --> Acute_inflammation Mast_cell --> Acute_inflammation PMN --> Phagocytosis MAC --> Phagocytosis Dendritic_cell --> Phagocytosis NK_cell --> Cytotoxicity end subgraph Adaptive_Immunity [Adaptive immunity] Specific_antigens[Specific antigens<br/>All bacteria, virus, etc.] --> B_cell Specific_antigens --> T_cell B_cell --> Antibody Antibody --> Entry_block_neutralization[Entry block<br/>neutralization toxin] end %% Interactions Antibody -.-> Adherence -.-> MAC Antibody -.-> Activation -.-> Complement MAC -.-> Activation -.-> T_cell Dendritic_cell -.-> Presentationn -.-> T_cell T_cell -.-> Help -.-> B_cell style Innate_Immunity fill:#f9d5d5,stroke:#333 style Adaptive_Immunity fill:#d5f0ff,stroke:#333 style Antibody fill:#e67e22 style Acute_inflammation fill:#e67e22 style Chronic_inflammation fill:#e67e22 style Complement fill:#f39c12 ```  **Innate immunity** - Virus -> Interferons -> Block - Some Bacteria -> Defensins -> Lysis - Some Bacteria -> Lysozyme -> Lysis - Injury -> Tissue_damage -> Acute_inflammation -> Healing - Some bacteria -> Tissue_damage -> Chronic_inflammation - Complement -> Mast_cell -> Acute_inflammation - Complement -> MAC -> Phagocytosis - Complement -> Acute_inflammation - PMN -> Phagocytosis - Dendritic_cell -> Phagocytosis - NK_cell -> Cytotoxicity **Adaptive immunity** - Specific antigens (All bacteria, virus, etc.) -> B_cell -> Antibody -> Entry_block/neutralization toxin - Specific antigens -> T_cell **Interactions** - Antibody -> Adherence -> MAC - Antibody -> Activation -> Complement - MAC -> Activation -> T_cell - Dendritic_cell -> Presentation -> T_cell - T_cell -> Help -> B_cell Labelled diagram illustrating the interaction between Innate immunity and Adaptive immunity. The diagram is split into two main sections: 'Innate immunity' (pink background) on the left and 'Adaptive immunity' (blue background) on the right. It shows various cells (Virus, Some Bacteria, Mast cell, PMN, MAC, Dendritic cell, NK cell, B cell, T cell), molecules (Interferons, Defensins, Lysozyme, Complement, Antibody), and processes (Block, Lysis, Acute inflammation, Chronic inflammation, Healing, Phagocytosis, Cytotoxicity). Arrows indicate relationships and interactions between these elements, such as 'Activation', 'Presentation', 'Help', and 'Adherence'. The bottom of the diagram categorizes components into 'Tissues', 'Myeloid cells', and 'Lymphocytes'. A logo for 'THE UNIVERSITY OF WESTERN AUSTRALIA' is present in the top right corner. **Dento–gingival host defenses** **THE UNIVERSITY OF WESTERN AUSTRALIA** Fig 7.2 Host defences against microbial plaque. | **Innate immune response & Adaptive immune response** | **Mediators** | | | :--- | :--- | :--- | | **Saliva** | **Epithelium** | **Inflammatory response** | **Humoral response** | **Cell-mediated response** | | Prevents drying of gingiva and teeth | Physical barrier | Fluid component | Antibody production | No antibody | | Antimicrobial effects via: | Inflammatory response via keratinocytes | Gingival crevicular fluid | | T-helper cells | | Swallowing bacteria | Immune response via Langerhans' cells | Cellular components | | | | Salivary IgA | | Neutrophils | | | | Salivary peroxidase | | Macrophages | | | | Lysozyme and lactoferrin | | | | | **Clerehugh et al 2013**  **Dento–gingival host defenses** **THE UNIVERSITY OF WESTERN AUSTRALIA** Fig 7.2 Host defences against microbial plaque. | Innate immune response & Adaptive immune response | Mediators | | | :--- | :--- | :--- | | **Saliva** | **Epithelium** | **Inflammatory response** | **Humoral response** | **Cell-mediated response** | | Prevents drying of gingiva and teeth | Physical barrier | Fluid component | Antibody production | No antibody | | Antimicrobial effects via: | Inflammatory response via keratinocytes | Gingival crevicular fluid | | T-helper cells | | Swallowing bacteria | Immune response via Langerhans' cells | Cellular components | | | | Salivary IgA | | Neutrophils | | | | Salivary peroxidase | | Macrophages | | | | Lysozyme and lactoferrin | | | | | **Clerehugh et al 2013** Flowchart diagram illustrating 'Dento–gingival host defenses' in response to 'Microbial plaque'. The diagram branches into 'Innate immune response' and 'Adaptive immune response', linked by a bidirectional arrow labeled 'Mediators'. Under 'Innate immune response', it details 'Saliva' (prevents drying, antimicrobial effects via swallowing bacteria, salivary IgA, peroxidase, lysozyme/lactoferrin), 'Epithelium' (physical barrier, inflammatory response via keratinocytes, immune response via Langerhans' cells), and 'Inflammatory response' (fluid component: gingival crevicular fluid; cellular components: neutrophils, macrophages). Under 'Adaptive immune response', it shows 'Humoral response' (antibody production) and 'Cell-mediated response' (no antibody, T-helper cells). Source cited as Clerehugh et al 2013. **Classical pathway** Via Ag-Ab complexes Microbe C1 IgG antibody **Lectin pathway** Via MBL-MASP complexes Microbe Mannose MASP1 MBL MASP2 **Alternative pathway** Via spontaneous C3 hydrolysis Microbe C3 >> C3b **C3** Self-amplification loop C3a C3b Opsonization for phagocytosis C5 C5a C5b C6 C7 C8 C9 Membrane attack complex **TLR** C3aR Cross-TALK or C5aR Inflammatory cell activation Inflammatory mediators Degradative enzymes Reactive oxygen species Ag presentation & adaptive immunity **Dysbiotic microbiome** Periodontitis Tooth Bone ? **Fig. 11.3 Complement activation and periodontal disease.** The complement system can be activated by distinct initiation mechanisms: The classical pathway is triggered by antigen-antibody complex-mediated activation of the C1 complex. The lectin pathway is initiated when complexes of mannose-binding lectin (*MBL*) and MBL-associated serine proteases (*MASPs*) recognize and adhere to microbial surfaces. The alternative pathway is triggered by a “tick-over” mechanism that involves spontaneous C3 hydrolysis, which occurs in the absence of complement regulatory molecules (as is typically the case with foreign surfaces such as microbial cells). In the so-called alternative pathway-amplification loop, additional C3 is cleaved into even more C3b which further fuels the loop, thereby amplifying complement activation irrespective of the initiating mechanism. All three mechanisms of complement initiation and amplification converge at C3. The downstream effects of C3 activation include the generation of effectors that promote inflammation (*C3a* and *C5a*), opsonization for phagocytosis (*C3b*) and the generation C5b-C9 membrane attack complex (MAC). MAC can lyse susceptible targeted bacteria but has also been implicated in destructive inflammation. Whereas the role of MAC in periodontitis is uncertain, **C3a** and **C5a** activate specific G-protein-coupled receptors (**C3aR** and **C5aR1**), which cross-talk with Toll-like receptors (**TLRs**). This cross-talk interaction between complement and TLRs activates synergistically inflammatory leukocytes, which directly or indirectly mediate destructive inflammation that leads to periodontal tissue breakdown and alveolar bone loss in periodontitis.  **Classical pathway** Via Ag-Ab complexes Microbe -> C1 -> IgG antibody **Lectin pathway** Via MBL-MASP complexes Microbe -> Mannose -> MASP1 -> MBL -> MASP2 **Alternative pathway** Via spontaneous C3 hydrolysis Microbe -> C3 >> C3b **C3** Self-amplification loop - C3a - C3b -> Opsonization for phagocytosis - C5 -> C5a -> C5b -> C6 -> C7 -> C8 -> C9 -> Membrane attack complex **TLR** C3aR or C5aR -> Cross-TALK -> Inflammatory cell activation -> Inflammatory mediators, Degradative enzymes, Reactive oxygen species, Ag presentation & adaptive immunity **Dysbiotic microbiome** -> Periodontitis -> Tooth -> Bone **Fig. 11.3 Complement activation and periodontal disease.** The complement system can be activated by distinct initiation mechanisms: The classical pathway is triggered by antigen-antibody complex-mediated activation of the C1 complex. The lectin pathway is initiated when complexes of mannose-binding lectin (*MBL*) and MBL-associated serine proteases (*MASPs*) recognize and adhere to microbial surfaces. The alternative pathway is triggered by a "tick-over" mechanism that involves spontaneous C3 hydrolysis, which occurs in the absence of complement regulatory molecules (as is typically the case with foreign surfaces such as microbial cells). In the so-called alternative pathway-amplification loop, additional C3 is cleaved into even more C3b which further fuels the loop, thereby amplifying complement activation irrespective of the initiating mechanism. All three mechanisms of complement initiation and amplification converge at C3. The downstream effects of C3 activation include the generation of effectors that promote inflammation (*C3a* and *C5a*), opsonization for phagocytosis (*C3b*) and the generation C5b-C9 membrane attack complex (MAC). MAC can lyse susceptible targeted bacteria but has also been implicated in destructive inflammation. Whereas the role of MAC in periodontitis is uncertain, **C3a** and **C5a** activate specific G-protein-coupled receptors (**C3aR** and **C5aR1**), which cross-talk with Toll-like receptors (**TLRs**). This cross-talk interaction between complement and TLRs activates synergistically inflammatory leukocytes, which directly or indirectly mediate destructive inflammation that leads to periodontal tissue breakdown and alveolar bone loss in periodontitis. Labelled biological pathway diagram illustrating the complement system's role in periodontitis. The diagram is divided into three main sections: initiation pathways on the left, downstream effects in the center, and clinical pathology on the right. Left Section (Initiation): - Classical pathway: Shows C1/IgG antibody complexes binding to a microbe. - Lectin pathway: Shows MBL/MASP complexes recognizing mannose on a microbe. - Alternative pathway: Shows spontaneous C3 hydrolysis on a microbe surface. All three pathways converge at C3. Center Section (Downstream Effects): - A self-amplification loop involving C3 cleavage into C3a and C3b. - C3a and C5a act as inflammatory mediators. - C3b leads to opsonization for phagocytosis. - C5b initiates the formation of the Membrane attack complex (MAC) composed of C6-C9. Right Section (Pathology & Cell Interaction): - Shows cross-talk between complement receptors (C3aR/C5aR) and Toll-like receptors (TLRs) on an inflammatory cell. - Results in Inflammatory cell activation (mediators, enzymes, ROS). - Depicts Dysbiotic microbiome causing Periodontitis, affecting Tooth and Bone. **Epithelium** **Dento- gingival junction** 1. Junctional epithelium (JE) 2. Sulcular epithelium 3. Oral epithelium 4. Epithelial rests of Malassez **JE functions** - attachment to tooth - barrier - rapid turnover - antimicrobial defence - GCF flow Physical barrier: turnover + peeling Biological barrier: defensins, IL-8, PMN   **Epithelium** **Dento-gingival junction** 1. Junctional epithelium (JE) 2. Sulcular epithelium 3. Oral epithelium 4. Epithelial rests of Malassez **JE functions** - attachment to tooth - barrier - rapid turnover - antimicrobial defence - GCF flow Physical barrier: turnover + peeling Biological barrier: defensins, IL-8, PMN Labelled schematic diagram illustrating the anatomical layers of the dento-gingival junction. Key labeled regions include: 1. Junctional epithelium (JE), 2. Sulcular epithelium, 3. Oral epithelium, and 4. Epithelial rests of Malassez. The figure visually demonstrates the JE's attachment to the tooth surface and includes a legend listing its functions: attachment to tooth, barrier, rapid turnover, antimicrobial defence, and GCF flow. Schematic cross-section of the gingival sulcus showing the epithelial lining. It depicts the specific cellular structure of the junctional epithelium attaching to the tooth surface via hemidesmosomes (represented as small red circles) and shows the direction of fluid flow or migration along the epithelial cells. Gingival crevicular fluid (GCF) **Inflammatory exudate** released through the crevice, resulting from the increase in permeability of vessels next to the JE and SE. **Composed of**: plasma derived substances (**antibodies**, **cytokines**, **enzymes**), epithelium and immune cells, bacteria. **GCF volume** and flow increase with increasing inflammation.   Gingival crevicular fluid (GCF) **Inflammatory exudate** released through the crevice, resulting from the increase in permeability of vessels next to the JE and SE. **Composed of**: plasma derived substances (**antibodies**, **cytokines**, **enzymes**), epithelium and immune cells, bacteria. **GCF volume** and flow increase with increasing inflammation. Labelled diagram illustrating the composition of gingival crevicular fluid (GCF) at the junction of tooth and gum. The diagram shows cross-sections of dental structures including enamel, dentin, pulp, cementum, and various layers of soft tissue. It depicts inflammatory processes with specific components labeled: B = bacteria, D = degradation products, E = epithelium, F = fibroblasts, N = neutrophils, OC = osteoclasts, S = serum. The visual demonstrates how GCF is formed through increased vascular permeability near the junctional epithelium (JE) and supracrestal epithelium (SE), releasing plasma-derived substances, immune cells, and bacteria into the crevice. Clinical photograph showing a close-up view of human teeth with visible gingival tissues. A metal dental instrument (likely a periodontal probe or scaler) is positioned vertically between two anterior teeth, demonstrating access to the gingival sulcus/crevice. The image visually supports the text's description of GCF being released through the crevice due to inflammation. **THE UNIVERSITY OF** **WESTERN** **AUSTRALIA** **Innate immunity** (rapid response) **Dendritic cell** **Mast cell** **Macrophage** **Natural killer cell** **Complement protein** **Basophil** **Eosinophil** Neutrophil **Granulocytes** **Adaptive immunity** (slow response) **$\gamma\delta$ T cell** **Natural killer T cell** **B cell** Antibodies **T cell** **CD4+ T cell** **CD8+ T cell**  **THE UNIVERSITY OF WESTERN AUSTRALIA** **Innate immunity (rapid response)** - Dendritic cell - Mast cell - Macrophage - Natural killer cell - Complement protein - Basophil - Eosinophil - Neutrophil - Granulocytes **Adaptive immunity (slow response)** - γδ T cell - Natural killer T cell - B cell - Antibodies - T cell - CD4+ T cell - CD8+ T cell Venn diagram comparing Innate immunity (rapid response) and Adaptive immunity (slow response). The left circle contains Dendritic cell, Mast cell, Macrophage, Natural killer cell, Complement protein, Basophil, Eosinophil, Neutrophil, and a bracket labeled Granulocytes. The right circle contains B cell with Antibodies, T cell branching into CD4+ T cell and CD8+ T cell. The intersection region contains γδ T cell and Natural killer T cell. # First defense cells (innate immunity) ### Figure 7.3 The role of neutrophils in phagocytosis or the killing of microorganisms. **If bacteria are in plaque matrix:** * Neutrophils attach to plaque matrix * Neutrophils secrete externally: * Enzymes * Hydrogen peroxide and hypochlorous acid * Neutrophils kill bacteria without phagocytosis * Plaque matrix dissolved * Washed away by gingival crevicular fluid * Bystander damage caused **If bacteria are unattached:** * Neutrophils recognise and bind to bacteria which are phagocytosed into phagocytic vacuole * Neutrophils produce and release: * Antibacterial granules * Hydrogen peroxide and hypochlorous acid * Enzymes digest microorganisms * Remnants expelled * Bystander damage caused *** ### Figure 7.4 The role of macrophages in inflammation and immunity. ```mermaid graph TD Macrophage --- INFLAMMATION Macrophage --- IMMUNITY subgraph INFLAMMATION A[Scavenger - responsible for phagocytosis of dead and dying cells] B[Modulates fluid and cellular components of inflammation] C[Secretes tissue-degrading enzymes] D["Secretes mediators, e.g. IL-1, TNF-α, prostaglandins"] end subgraph IMMUNITY E[Traps and presents antigens in the connective tissue while CD44 acts as anchor] F["Secretes IL-1 and TNF-α"] end Macrophage --- A Macrophage --- B Macrophage --- C Macrophage --- D Macrophage --- E Macrophage --- F ``` Clerehugh et al 2013   **First defense cells (innate immunity)** **Figure 7.3 The role of neutrophils in phagocytosis or the killing of microorganisms.** **If bacteria are in plaque matrix:** - Neutrophils attach to plaque matrix - Neutrophils secrete externally: - Enzymes - Hydrogen peroxide and hypochlorous acid - Neutrophils kill bacteria without phagocytosis - Plaque matrix dissolved - Washed away by gingival crevicular fluid - Bystander damage caused **If bacteria are unattached:** - Neutrophils recognise and bind to bacteria which are phagocytosed into phagocytic vacuole - Neutrophils produce and release: - Antibacterial granules - Hydrogen peroxide and hypochlorous acid - Enzymes digest microorganisms - Remnants expelled - Bystander damage caused **Figure 7.4 The role of macrophages in inflammation and immunity.** **INFLAMMATION** - Scavenger - responsible for phagocytosis of dead and dying cells - Modulates fluid and cellular components of inflammation - Secretes tissue-degrading enzymes - Secretes mediators, e.g. IL-1, TNF-α, prostaglandins **IMMUNITY** - Traps and presents antigens in the connective tissue while CD44 acts as anchor - Secretes IL-1 and TNF-α Clerehugh et al 2013 A composite figure consisting of a diagram and two text boxes. On the left is a purple illustration of a neutrophil with small dots representing bacteria inside it. To the right are two vertical panels: one titled 'If bacteria are in plaque matrix' listing steps like attachment, secretion, and dissolution; the other titled 'If bacteria are unattached' detailing recognition, phagocytosis, and release of antibacterial granules. A central diagram of a macrophage cell surrounded by six labeled callout boxes. These boxes categorize functions into 'INFLAMMATION' (scavenging dead cells, modulating fluid components, secreting enzymes/mediators) and 'IMMUNITY' (antigen trapping/presentation via CD44, secreting IL-1 and TNF-alpha). The text on the page only makes sense in the context of the diagram (labels such as "Complement," "Antibody," "T-cell," "MMP-8," etc.), and its meaning is entirely dependent on the visual elements. Per the instructions, the entire content should be treated as a single figure.   The text on the page only makes sense in the context of the diagram (labels such as "Complement," "Antibody," "T-cell," "MMP-8," etc.), and its meaning is entirely dependent on the visual elements. Per the instructions, the entire content should be treated as a single figure. Clinical histology photograph of gingival tissue showing inflammation. The image displays a section of oral mucosa with distinct layers: the stratified squamous epithelium on top (pink/purple), the lamina propria in the middle, and underlying connective tissue. The tissue architecture is disrupted by inflammatory infiltrate. Schematic diagram illustrating the pathogenesis of periodontal disease. It depicts the interaction between host immune cells (T-cell, B-cell, Plasma cell, Macrophage, Osteoclast) and Periodontal bacteria. Key processes shown include Phagocytosis, Antibody production, and the release of inflammatory mediators like IL-1β, TNF-α, MMP-1, and MMP-8 leading to bone resorption. Blue arrows overlay the image connecting specific regions of the histology photo to corresponding components in the schematic. Adaptive immunity **Neutralization** **Opsonization and Fc receptor-mediated phagocytosis** **Bacterial lysis** **Inflammation** **Phagocytosis of C3b-coated bacteria** **Antibody response** **Macrophage activation ⇒ Phagocytosis and bacterial killing** **Inflammation** Figure 15–1 **Adaptive immune responses to extracellular microbes.** Adaptive immune responses to extracellular microbes, such as bacteria, and their toxins consist of antibody production and the activation of CD4+ helper T cells. Antibodies neutralize and eliminate microbes and toxins by several mechanisms. Helper T cells produce cytokines that stimulate B cell responses, macrophage activation, and inflammation. APC, antigen-presenting cell; INF-γ, interferon-γ; TNF, tumor necrosis factor.  Adaptive immunity **Neutralization** **Opsonization and Fc receptor-mediated phagocytosis** **Bacterial lysis** **Inflammation** **Phagocytosis of C3b-coated bacteria** **Antibody response** **Macrophage activation ⇒ Phagocytosis and bacterial killing** **Inflammation** Figure 15–1 **Adaptive immune responses to extracellular microbes.** Adaptive immune responses to extracellular microbes, such as bacteria, and their toxins consist of antibody production and the activation of CD4+ helper T cells. Antibodies neutralize and eliminate microbes and toxins by several mechanisms. Helper T cells produce cytokines that stimulate B cell responses, macrophage activation, and inflammation. APC, antigen-presenting cell; INF-γ, interferon-γ; TNF, tumor necrosis factor. A complex labelled diagram illustrating adaptive immune responses to extracellular microbes. The image is divided into two main sections: the top half details antibody-mediated mechanisms (Neutralization, Opsonization, Bacterial lysis, Inflammation, Phagocytosis of C3b-coated bacteria), while the bottom half depicts CD4+ helper T cell activation pathways leading to various cytokine production and subsequent effects like Macrophage activation and Inflammation. THE UNIVERSITY OF WESTERN AUSTRALIA **IN**NATE & **A**DAPTIVE **IM**MUNITY  INNATE & ADAPTIVE IMMUNITY Title slide graphic featuring the text 'INNATE & ADAPTIVE IMMUNITY' with cartoon virus characters below. **HUMORAL RESPONSE** 1. Plaque antigens diffuse through the junctional epithelium 2. Langerhans cells within the epithelium capture and process the antigens 3. Antigen-presenting cells (Macrophages and Langerhans cells) leave the gingiva in the lymphatics 4. Antigen-presenting cells reach the lymph node and begin to stimulate lymphocytes to produce a specific immune response 5. Periodontal microbe specific antibodies are produced by plasma cells within the lymph nodes and travel back to the gingiva via blood vessels 6. Antibodies leave the circulation and are carried to the crevice in the transudate from the inflamed and dilated blood vessels 7. Antibody action on microbes in the crevice can result in killing, aggregation, precipitation, detoxification, opsonization and phagocytosis of bacteria  **HUMORAL RESPONSE** 1. Plaque antigens diffuse through the junctional epithelium 2. Langerhans cells within the epithelium capture and process the antigens 3. Antigen-presenting cells (Macrophages and Langerhans cells) leave the gingiva in the lymphatics 4. Antigen-presenting cells reach the lymph node and begin to stimulate lymphocytes to produce a specific immune response 5. Periodontal microbe specific antibodies are produced by plasma cells within the lymph nodes and travel back to the gingiva via blood vessels 6. Antibodies leave the circulation and are carried to the crevice in the transudate from the inflamed and dilated blood vessels 7. Antibody action on microbes in the crevice can result in killing, aggregation, precipitation, detoxification, opsonization and phagocytosis of bacteria Labelled diagram illustrating the Humoral Response in periodontal tissue. The central image depicts the junctional epithelium and underlying connective tissue with numbered steps indicating the immune process: (1) plaque antigens diffusing through the junctional epithelium; (2) Langerhans cells capturing and processing antigens; (3) antigen-presenting cells leaving gingiva via lymphatics; (4) cells reaching a lymph node to stimulate lymphocytes; (5) antibodies produced by plasma cells traveling back via blood vessels; (6) antibodies entering the crevice via transudate from dilated blood vessels; and (7) antibody action on microbes resulting in killing or opsonization. The University of Western Australia Adaptive - Cell-mediated response Antigen penetration of JE => APC + T cell naïve => Different subsets of T-helper cells (**Th1, Th2, Th17, T reg**) proliferate and release different cytokines profiles Th1: IL-2, IFN-g, Th2: IL-4, IL-5 Th17: IL-17 T reg: IL-10, TGF-b Cytokines act on other cells (PMN, macrophages, B or T cells) to stimulate, inhibit or kill T-helper cells on re-exposure proliferate and produce cytokines (memory) Fig. 1 The potential role of distinct T cell subsets in inflammatory responses and alveolar bone resorption in periodontitis lesions. As a consequence of sustained infection by periodontopathic bacteria, an adaptive immune response is established. NKT cells are involved in shaping the course of the immune response. Th1, Th2, and Th17 cells contribute to infection control in different ways because of their distinct cytokine profiles. However, their action also enhances inflammatory responses that lead to periodontal tissue destruction. Particularly, Th17 cells have a high potential to facilitate osteoclastogenesis through the production of IL-17 to induce RANKL expression on osteoblasts, enhancement of local inflammation, and RANKL expression on themselves. However, Tregs attenuate the inflammatory responses by suppressing other immune cells and inhibit osteoclastogenesis; therefore, they could protect against tissue destruction. Enhanced inflammation may convert a fraction of Tregs to IL-17-producing cells. Mφ macrophage, Ob osteoblast  The University of Western Australia Adaptive - Cell-mediated response Antigen penetration of JE => APC + T cell naïve => Different subsets of T-helper cells (**Th1, Th2, Th17, T reg**) proliferate and release different cytokines profiles - Th1: IL-2, IFN-g - Th2: IL-4, IL-5 - Th17: IL-17 - T reg: IL-10, TGF-b Cytokines act on other cells (PMN, macrophages, B or T cells) to stimulate, inhibit or kill T-helper cells on re-exposure proliferate and produce cytokines (memory) Fig. 1 The potential role of distinct T cell subsets in inflammatory responses and alveolar bone resorption in periodontitis lesions. As a consequence of sustained infection by periodontopathic bacteria, an adaptive immune response is established. NKT cells are involved in shaping the course of the immune response. Th1, Th2, and Th17 cells contribute to infection control in different ways because of their distinct cytokine profiles. However, their action also enhances inflammatory responses that lead to periodontal tissue destruction. Particularly, Th17 cells have a high potential to facilitate osteoclastogenesis through the production of IL-17 to induce RANKL expression on osteoblasts, enhancement of local inflammation, and RANKL expression on themselves. However, Tregs attenuate the inflammatory responses by suppressing other immune cells and inhibit osteoclastogenesis; therefore, they could protect against tissue destruction. Enhanced inflammation may convert a fraction of Tregs to IL-17-producing cells. Mφ macrophage, Ob osteoblast Labelled biological diagram illustrating the adaptive cell-mediated immune response in periodontitis lesions. The diagram depicts various immune cell types including APC, B cells, Mφ (macrophages), Ob (osteoblasts), Treg, Th1, Th2, Th17, and NKT cells. It shows interactions between these cells via arrows indicating cytokine release (e.g., IL-4, IL-17, IL-23) and signaling pathways (e.g., CTIA-4, RANKL). Key processes such as osteoclastogenesis are highlighted with callouts. The visual demonstrates how different T-helper subsets influence inflammation and bone resorption. # Immune response = cells+mediators ✓ Main aim is to control infection in different ways ✓ Connective tissue destruction in periodontitis occurs as a “side-effect” of the immune-inflammatory response ✓ Perio ligament and bone destruction in periodontitis: * *Biofilm essential, but not sufficient* * **High levels of pro-inflammatory cytokines (IL1b, TNFa), prostaglandins, MMP's, RANKL** * **Low levels of anti-inflammatory mediators (IL-10, TGF-b, TIMPs and OPG**  **Immune response = cells+mediators** - Main aim is to control infection in different ways - Connective tissue destruction in periodontitis occurs as a "side-effect" of the immune-inflammatory response - Perio ligament and bone destruction in periodontitis: - *Biofilm essential, but not sufficient* - **High levels of pro-inflammatory cytokines (IL1b, TNFa), prostaglandins, MMP's, RANKL** - **Low levels of anti-inflammatory mediators (IL-10, TGF-b, TIMPs and OPG** A labelled biological pathway diagram illustrating the immune response mechanism. It depicts bacterial pathogens (LPS) triggering a cascade involving Th1, Th17, and Th2 cells releasing cytokines like IFN-gamma, IL-17, and IL-4. These signals lead to the production of pro-inflammatory mediators (TNF-alpha, IL-1b) which activate MMPs and RANKL, resulting in ECM degradation and bone resorption. Conversely, Tregs release IL-10 and OPG to inhibit this process via TIMPs. ```mermaid graph TD PB(Periodontal bacteria) --> LPS(LPS) PB --> PRG(Peripheral dentritic cell) PB --> PH1(Phagocytosis) LPS --> AB(Activated B-cell) LPS --> MAC(Macrophage) PRG --> T(T-cell) T --> B(B-cell) B --> T B --> P(Plasma cell) P --> T P --> ANT(Antibody) ANT --> COM(Complement) MAC --> IL1(IL-1β TNF-α) MAC --> MMP1(MMP-1) IL1 --> FIB(Fibroblast) IL1 --> OST(Osteoclast activation) FIB --> MMP1 OST --> Bone(Bone) PH1 --> MMP8_1(MMP-8) MMP1 --> PMN(PMN) MMP8_1 --> PMN ICAM1(IL-8 ICAM-1) --> PMN ```   Periodontal bacteria -> LPS -> Activated B-cell Periodontal bacteria -> Peripheral dentitic cell -> T-cell -> B-cell -> Plasma cell -> Antibody -> Complement Periodontal bacteria -> Phagocytosis -> MMP-8 -> PMN LPS -> Macrophage -> IL-1β TNF-α -> Fibroblast -> MMP-1 -> PMN LPS -> Macrophage -> IL-1β TNF-α -> Osteoclast activation -> Bone T-cell -> B-cell B-cell -> T-cell IL-8 ICAM-1 -> PMN Clinical histology photograph of a periodontal tissue section. The image displays the stratified squamous epithelium on the left and underlying connective tissue with inflammatory infiltrate extending into the bone trabeculae at the bottom. Schematic diagram illustrating the pathogenesis of periodontitis. It shows the interaction between Periodontal bacteria, immune cells (T-cell, B-cell, Plasma cell, Macrophage, Osteoclast), and host mediators (Antigen, LPS, Antibody, Complement, IL-1β, TNF-α, MMP-1, MMP-8). Blue arrows indicate correspondence to regions in the adjacent histology photo. 332 Current Osteoporosis Reports (2023) 21:330–343 **Macitentan** **Denosumab**  332 Current Osteoporosis Reports (2023) 21:330–343 **Macitentan** **Denosumab** Biological pathway diagram illustrating osteoclast differentiation and bone resorption. The flow begins at the top left with 'Osteoblasts precursor' transforming into 'Osteoblasts'. From Osteoblasts, two pathways emerge: one producing 'RANKL' (blue spheres) and another producing 'OPG' (pink spheres). A dashed arrow indicates that Macitentan inhibits the transformation from precursor to Osteoblasts. Another dashed line shows Denosumab inhibiting the binding of RANKL to its receptor. RANKL binds to 'RANK' on an 'Osteoclast precursor', leading to its maturation into an 'Osteoclast'. Finally, the Osteoclast is shown performing 'Bone Resorption' on a block of bone tissue. The University of Western Australia logo appears in the top right corner.  Labelled diagram of the bone remodeling cycle on a trabecula. The image shows a cross-section of bone tissue with various cellular components and stages labeled. Key elements include: 'Blood vessel' at the top containing red blood cells; 'Lining cells' covering the bone surface; 'Microcrack' in the bone matrix; 'Osteocyte apoptosis' showing dying osteocytes; 'Osteoclasts' (large green multinucleated cells) actively resorbing bone near a microcrack; 'Local factors' released from blood vessels influencing the process; 'Osteoblasts' involved in new bone formation; 'New lining cells'; 'New osteocytes'; 'Osteoid' layer; 'New bone'; 'Cement line'; and 'Old bone'. A pink circle highlights the area of active resorption and apoptosis, with a large purple arrow pointing towards this region from the title. **OSTEOCLASTS ACTIVATION** **RANKL & OSTEOPROTEGERIN OPG STIMULATE OSTEOCLASTO-GENESIS AND BONE RESORPTION.** **RANKL /OPG HIGH RATIO PRORESORPTIVE.** **RANKL /OPG LOW RATIO ANTIRESORPTIVE.** ACTIVATED T AND B CELLS CELLULAR SOURCE FOR RANKL **IFN-γ AND IL-17 INCREASE RANKL** **IL-4 & IL-10 REDUCE RANKL/OPG RATIO** LYMPHOCYTES SUBSETS TH1 & TH17 PRO RESORPTIVE **TH2 & Tregs (Regulatory T) antiresorptive**  **OSTEOCLASTS ACTIVATION** **RANKL & OSTEOPROTEGERIN OPG STIMULATE OSTEOCLASTOGENESIS AND BONE RESORPTION.** **RANKL /OPG HIGH RATIO PRORESORPTIVE.** **RANKL /OPG LOW RATIO ANTIRESORPTIVE.** ACTIVATED T AND B CELLS CELLULAR SOURCE FOR RANKL **IFN-γ AND IL-17 INCREASE RANKL** **IL-4 & IL-10 REDUCE RANKL/OPG RATIO** LYMPHOCYTES SUBSETS TH1 & TH17 PRO RESORPTIVE **TH2 & Tregs (Regulatory T) antiresorptive** Complex biological pathway diagram illustrating the regulation of osteoclasts activation. The diagram is split into two main sections: 'HOMEOSTATIC CONDITIONS' (RANKL < OPG) and 'INFLAMMATORY CONDITIONS' (RANKL > OPG). It depicts cellular interactions including Th1 cells secreting IFN-γ, Th17 cells secreting IL-17, Th2 cells secreting IL-4, and Tregs secreting IL-10. These cytokines influence RANKL and OPG levels, leading to bone resorption or inhibition thereof.    Clinical photo showing a healthy mouth with pink, non-swollen gums and white teeth. Clinical photo showing gingivitis. A dental probe is being used to measure the pocket depth on inflamed gums, which appear red and swollen. Clinical photo showing periodontitis. A dental probe is measuring deep pockets in severely inflamed, red gums that have receded from the teeth. # Histopathology of periodontal diseases **PRISTINE GINGIVA** x Histologic Perfection   **Histopathology of periodontal diseases** **PRISTINE GINGIVA** x Histologic Perfection Clinical photograph of the anterior teeth and gingiva showing healthy pink tissue with stippling and no signs of inflammation or bleeding. Labeled anatomical cross-section diagram illustrating pristine gingiva histology, including enamel, junctional epithelium, cementum, alveolar bone, and periodontal ligament, with annotations indicating shallow gingival sulcus and sparse neutrophil migration. - Clinically healthy gingiva with a limited coronal infiltrate (5-10% of the connective tissue area) - Neutrophils and monocytes in JE - Lymphocytes in the connective tissue - Increase in vascular structures near JE - Exudative fluid from vessels to tissues= GCF  - Clinically healthy gingiva with a limited coronal infiltrate (5-10% of the connective tissue area) - Neutrophils and monocytes in JE - Lymphocytes in the connective tissue - Increase in vascular structures near JE - Exudative fluid from vessels to tissues = GCF Labelled diagram of an initial gingival lesion. The illustration shows a cross-section of the junctional epithelium and connective tissue near the tooth surface. Callouts point to: 'Initial plaque biofilm formation supragingivally' at the top; 'Increased neutrophil migration' in the plaque area; 'A few neutrophils and monocytes appear in junctional epithelium' within the epithelial layer; and 'Increased vascularity in connective tissue' showing vessels below the epithelium. A toothbrush is depicted brushing against the gum line. **INITIAL LESION histologically = gingival health clinically** • **24 HOURS PLAQUE ACCUMULATION** • **CHANGE IN MICROVASCULAR PLEXUS JE** • **ARTERIOLAS, CAPILLARIES AND VENULES DILATION** • **HYDROSTATIC PRESSURE INCREASE** • **INCREASED PERMEABILITY** • **EXUDATE OF FLUIDS & PROTEINS** • **INCREASED GCF** • **ENHANCED PMNS MIGRATION** • **PMNS ACCUMULATE IN JE AND SULCUS**  **INITIAL LESION histologically = gingival health clinically** - **24 HOURS PLAQUE ACCUMULATION** - **CHANGE IN MICROVASCULAR PLEXUS JE** - **ARTERIOLAS, CAPILLARIES AND VENULES DILATION** - **HYDROSTATIC PRESSURE INCREASE** - **INCREASED PERMEABILITY** - **EXUDATE OF FLUIDS & PROTEINS** - **INCREASED GCF** - **ENHANCED PMNS MIGRATION** - **PMNS ACCUMULATE IN JE AND SULCUS** Anatomical cross-section diagram of gingival tissue illustrating the histological changes during an initial lesion. The image shows a tooth section with plaque biofilm formation supragingivally and increased neutrophil migration in the sulcus. Callouts indicate 'A few neutrophils and monocytes appear in junctional epithelium' and 'Increased vascularity in connective tissue'. The visual depicts the microvascular plexus changes described in the text, including arterioles, capillaries, and venules dilation. EARLY LESION x Early Gingivitis (The University of Western Australia logo) • One week after plaque accumulation • **JE** blood vessels remain dilated • Increased in number and size of vasculature • Infiltrate predominant PMNs and lymphocytes = now 15-20% volume • Very few plasma cells • Initial fibroblast degeneration and collagen destruction • Proliferation of basal and **JE** cells • Coronal rete pegs • Inflammation clinically detected – bleeding – due to pocket epithelium ulceration **Figure 8.4 An early lesion.** (Labels pointing to diagram text): Increased plaque biofilm formation Neutrophil migration continues Rete peg proliferation in coronal junctional epithelium Lymphocytes appear Early damage to fibroblasts and loss of gingival collagen Intact alveolar bone Base of junctional epithelium still at cement-enamel junction *pocket epithelium ulceration*  EARLY LESION x Early Gingivitis (The University of Western Australia logo) - One week after plaque accumulation - **JE** blood vessels remain dilated - Increased in number and size of vasculature - Infiltrate predominant PMNs and lymphocytes = now 15-20% volume - Very few plasma cells - Initial fibroblast degeneration and collagen destruction - Proliferation of basal and **JE** cells - Coronal rete pegs - Inflammation clinically detected – bleeding – due to pocket epithelium ulceration **Figure 8.4 An early lesion.** (Labels pointing to diagram text): - Increased plaque biofilm formation - Neutrophil migration continues - Rete peg proliferation in coronal junctional epithelium - Lymphocytes appear - Early damage to fibroblasts and loss of gingival collagen - Intact alveolar bone - Base of junctional epithelium still at cement-enamel junction *pocket epithelium ulceration* Labelled diagram of an early gingival lesion (Early Gingivitis). The illustration depicts a cross-section of gum tissue adjacent to a tooth structure. Key features include increased plaque biofilm formation at the top and neutrophil migration continuing downwards. The coronal junctional epithelium shows rete peg proliferation. Lymphocytes are appearing within the tissue. Early damage is noted in fibroblasts and loss of gingival collagen. The base of the junctional epithelium remains attached to the cement-enamel junction. Below the soft tissue, intact alveolar bone is visible. Callout lines connect these labels to specific anatomical areas. <ul> <li>Increased fluid and leukocyte migration</li> <li>More edematous swelling clinically</li> <li>Plasma cells 10-30 % on coronal connective tissue</li> <li>Collagen loss in apical and lateral directions</li> <li>Inflammatory cell infiltrate expands</li> <li>Extension of rete pegs into connective tissue</li> <li>JE deattached to tooth surface</li> <li>Pocket epithelium with heavy cell infiltrate PMNs</li> <li>Permeable and ulcerated pocket epithelium</li> </ul>   - Increased fluid and leukocyte migration - More edematous swelling clinically - Plasma cells 10-30 % on coronal connective tissue - Collagen loss in apical and lateral directions - Inflammatory cell infiltrate expands - Extension of rete pegs into connective tissue - JE deattached to tooth surface - Pocket epithelium with heavy cell infiltrate PMNs - Permeable and ulcerated pocket epithelium Labelled diagram of an established gingival lesion showing anatomical changes including supragingival plaque extending subgingivally, deepened gingival sulcus (false gingival pocket), continued neutrophil migration, lateral proliferation of the junctional epithelium and rete peg proliferation, inflammatory cell infiltrate increasingly plasma cell dominated (10-30%), most coronal connective tissue attachment level at the cement-enamel junction, and alveolar bone still intact. Clinical photograph showing a patient's mouth with visible signs of gingivitis, including redness, swelling, and inflammation of the gum tissue along the lower teeth. **TABLE 15.2** Hallmarks of Gingivitis <table> <thead> <tr> <th>Feature</th> <th>Healthy Gingiva</th> <th>Gingivitis</th> </tr> </thead> <tbody> <tr> <td>Color</td> <td>Coral pink</td> <td>Red</td> </tr> <tr> <td>Contour</td> <td>Knife-edged and scalloped</td> <td>Rolled with bulbous papillae</td> </tr> <tr> <td>Consistency and texture</td> <td>Firm and resilient with stippling of the attached gingiva</td> <td>Edematous and with loss of stippling</td> </tr> </tbody> </table>  **TABLE 15.2** Hallmarks of Gingivitis | Feature | Healthy Gingiva | Gingivitis | | :--- | :--- | :--- | | Color | Coral pink | Red | | Contour | Knife-edged and scalloped | Rolled with bulbous papillae | | Consistency and texture | Firm and resilient with stippling of the attached gingiva | Edematous and with loss of stippling | A table titled 'Hallmarks of Gingivitis' comparing features of Healthy Gingiva versus Gingivitis across three categories: Color (Coral pink vs Red), Contour (Knife-edged and scalloped vs Rolled with bulbous papillae), and Consistency and texture (Firm and resilient with stippling of the attached gingiva vs Edematous and with loss of stippling). **THE UNIVERSITY OF WESTERN AUSTRALIA** CHAPTER 15 Dental Biofilm-Induced Gingivitis and Its Management 205 **TABLE 15.1 Stages of Gingivitis** | Stage | Time (Days) | Blood Vessels | Junctional and Sulcular Epithelia | Predominant Immune Cells | Collagen | Clinical Findings | |:-:|:-:|:-:|:-:|:-:|:-:|:-:| | I. Initial lesion | 2−4 | Vascular dilation Vasculitis | Infiltration by PMNs | PMNs | Perivascular loss | Gingival fluid flow | | II. Early lesion | 4−7 | Vascular proliferation | Same as stage I Rete pegs Atrophic areas | Lymphocytes | Increased loss around infiltrate | Erythema Bleeding on probing | | III. Established lesion | 14−21 | Same as stage II, plus blood stasis | Same as stage II but more advanced | Plasma cells | Continued loss | Changes in color, size, texture, and so on | **PMNs**, Polymorphonuclear leukocytes (neutrophils).  CHAPTER 15 Dental Biofilm-Induced Gingivitis and Its Management 205 **TABLE 15.1 Stages of Gingivitis** | Stage | Time (Days) | Blood Vessels | Junctional and Sulcular Epithelia | Predominant Immune Cells | Collagen | Clinical Findings | |:-:|:-:|:-:|:-:|:-:|:-:|:-:| | I. Initial lesion | 2−4 | Vascular dilation Vasculitis | Infiltration by PMNs | PMNs | Perivascular loss | Gingival fluid flow | | II. Early lesion | 4−7 | Vascular proliferation | Same as stage I Rete pegs Atrophic areas | Lymphocytes | Increased loss around infiltrate | Erythema Bleeding on probing | | III. Established lesion | 14−21 | Same as stage II, plus blood stasis | Same as stage II but more advanced | Plasma cells | Continued loss | Changes in color, size, texture, and so on | **PMNs**, Polymorphonuclear leukocytes (neutrophils). A structured table titled 'Stages of Gingivitis' listing three stages (Initial lesion, Early lesion, Established lesion) with columns for Time (Days), Blood Vessels, Junctional and Sulcular Epithelia, Predominant Immune Cells, Collagen, and Clinical Findings. Includes footnote defining PMNs. # **ADVANCED LESION x Periodontitis** ## **Advanced lesion** * Apical plaque growth * Apical migration of JE from CEJ * Lateral & apical extension of infiltrate * Alveolar bone loss starts * Extensive collagen fiber damage * Plasma cells predominantly (>50%)    **ADVANCED LESION x Periodontitis** **Advanced lesion** - Apical plaque growth - Apical migration of JE from CEJ - Lateral & apical extension of infiltrate - Alveolar bone loss starts - Extensive collagen fiber damage - Plasma cells predominantly (>50%) Labelled diagram illustrating an incipient periodontitis lesion. Key features include shallow pocket formation with neutrophil migration, ulcerated and leaky pocket epithelium, subgingival calculus covered by plaque, heavy inflammatory infiltrate with plasma cell density >50%, connective tissue attachment level 1–2 mm apical to cement-enamel junction, and incipient alveolar bone loss forming a suprabony pocket. The diagram also labels the cement-enamel junction and shows a pocket depth of 4–5 mm. Detailed labelled diagram of an advanced periodontitis lesion. Features include supragingival plaque extending subgingivally, deep periodontal pocket of 6 mm or more, heavy inflammatory infiltrate with plasma cells density >50%, subgingival calculus covered by plaque, ulcerated and leaky pocket epithelium, loss of connective tissue attachment of 3–4 mm, and alveolar bone loss forming an infrabony pocket. Labels point to specific anatomical and pathological structures. Clinical photograph showing teeth with signs of moderate chronic periodontitis. Visible features include swollen and inflamed gingiva, recession of the gum line, blunted gingival margins, and loss of tooth contour due to tissue destruction. This image provides a real-world example of the histological changes described in the diagrams. Thank you!!! **THE UNIVERSITY OF WESTERN AUSTRALIA** SEEK WISDOM  Thank you!!! **THE UNIVERSITY OF WESTERN AUSTRALIA** SEEK WISDOM A night sky photo showing stars and the Milky Way galaxy, used as a background for the slide. [^1]: Original PDF page 1: [[L5Etiopathogenesis 2.pdf#page=1|L5Etiopathogenesis 2, p.1]] [^2]: Original PDF page 2: [[L5Etiopathogenesis 2.pdf#page=2|L5Etiopathogenesis 2, p.2]] [^3]: Original PDF page 3: [[L5Etiopathogenesis 2.pdf#page=3|L5Etiopathogenesis 2, p.3]] [^4]: Original PDF page 4: [[L5Etiopathogenesis 2.pdf#page=4|L5Etiopathogenesis 2, p.4]] [^5]: Original PDF page 5: [[L5Etiopathogenesis 2.pdf#page=5|L5Etiopathogenesis 2, p.5]] [^6]: Original PDF page 6: [[L5Etiopathogenesis 2.pdf#page=6|L5Etiopathogenesis 2, p.6]] [^7]: Original PDF page 7: [[L5Etiopathogenesis 2.pdf#page=7|L5Etiopathogenesis 2, p.7]] [^8]: Original PDF page 8: [[L5Etiopathogenesis 2.pdf#page=8|L5Etiopathogenesis 2, p.8]] [^9]: Original PDF page 9: [[L5Etiopathogenesis 2.pdf#page=9|L5Etiopathogenesis 2, p.9]] [^10]: Original PDF page 10: [[L5Etiopathogenesis 2.pdf#page=10|L5Etiopathogenesis 2, p.10]] [^11]: Original PDF page 11: [[L5Etiopathogenesis 2.pdf#page=11|L5Etiopathogenesis 2, p.11]] [^12]: Original PDF page 12: [[L5Etiopathogenesis 2.pdf#page=12|L5Etiopathogenesis 2, p.12]] [^13]: Original PDF page 13: [[L5Etiopathogenesis 2.pdf#page=13|L5Etiopathogenesis 2, p.13]] [^14]: Original PDF page 14: [[L5Etiopathogenesis 2.pdf#page=14|L5Etiopathogenesis 2, p.14]] [^15]: Original PDF page 15: [[L5Etiopathogenesis 2.pdf#page=15|L5Etiopathogenesis 2, p.15]] [^16]: Original PDF page 16: [[L5Etiopathogenesis 2.pdf#page=16|L5Etiopathogenesis 2, p.16]] [^17]: Original PDF page 17: [[L5Etiopathogenesis 2.pdf#page=17|L5Etiopathogenesis 2, p.17]] [^18]: Original PDF page 18: [[L5Etiopathogenesis 2.pdf#page=18|L5Etiopathogenesis 2, p.18]] [^19]: Original PDF page 19: [[L5Etiopathogenesis 2.pdf#page=19|L5Etiopathogenesis 2, p.19]] [^20]: Original PDF page 20: [[L5Etiopathogenesis 2.pdf#page=20|L5Etiopathogenesis 2, p.20]] [^21]: Original PDF page 21: [[L5Etiopathogenesis 2.pdf#page=21|L5Etiopathogenesis 2, p.21]] [^22]: Original PDF page 22: [[L5Etiopathogenesis 2.pdf#page=22|L5Etiopathogenesis 2, p.22]] [^23]: Original PDF page 23: [[L5Etiopathogenesis 2.pdf#page=23|L5Etiopathogenesis 2, p.23]] [^24]: Original PDF page 24: [[L5Etiopathogenesis 2.pdf#page=24|L5Etiopathogenesis 2, p.24]] [^25]: Original PDF page 25: [[L5Etiopathogenesis 2.pdf#page=25|L5Etiopathogenesis 2, p.25]] [^26]: Original PDF page 26: [[L5Etiopathogenesis 2.pdf#page=26|L5Etiopathogenesis 2, p.26]] [^27]: Original PDF page 27: [[L5Etiopathogenesis 2.pdf#page=27|L5Etiopathogenesis 2, p.27]] [^28]: Original PDF page 28: [[L5Etiopathogenesis 2.pdf#page=28|L5Etiopathogenesis 2, p.28]] [^29]: Original PDF page 29: [[L5Etiopathogenesis 2.pdf#page=29|L5Etiopathogenesis 2, p.29]] [^30]: Original PDF page 30: [[L5Etiopathogenesis 2.pdf#page=30|L5Etiopathogenesis 2, p.30]] [^31]: Original PDF page 31: [[L5Etiopathogenesis 2.pdf#page=31|L5Etiopathogenesis 2, p.31]] [^32]: Original PDF page 32: [[L5Etiopathogenesis 2.pdf#page=32|L5Etiopathogenesis 2, p.32]] [^33]: Original PDF page 33: [[L5Etiopathogenesis 2.pdf#page=33|L5Etiopathogenesis 2, p.33]] [^34]: Original PDF page 34: [[L5Etiopathogenesis 2.pdf#page=34|L5Etiopathogenesis 2, p.34]] [^35]: Original PDF page 35: [[L5Etiopathogenesis 2.pdf#page=35|L5Etiopathogenesis 2, p.35]] [^36]: Original PDF page 36: [[L5Etiopathogenesis 2.pdf#page=36|L5Etiopathogenesis 2, p.36]] [^37]: Original PDF page 37: [[L5Etiopathogenesis 2.pdf#page=37|L5Etiopathogenesis 2, p.37]] [^38]: Original PDF page 38: [[L5Etiopathogenesis 2.pdf#page=38|L5Etiopathogenesis 2, p.38]] [^39]: Original PDF page 39: [[L5Etiopathogenesis 2.pdf#page=39|L5Etiopathogenesis 2, p.39]] [^40]: Original PDF page 40: [[L5Etiopathogenesis 2.pdf#page=40|L5Etiopathogenesis 2, p.40]] [^41]: Original PDF page 41: [[L5Etiopathogenesis 2.pdf#page=41|L5Etiopathogenesis 2, p.41]]