Lung defence_.pdf

O2/02/24 Lung defence: Learning objective: describe innate and acquired responses. Learning objective: describe the role of macrophages, neutrophils and lymphocytes in host defence. Learning objective: describe the importance of immunoglobulins in lung defence. Learning objective: appreciate the rol...

O2/02/24 Lung defence: Learning objective: describe innate and acquired responses. Learning objective: describe the role of macrophages, neutrophils and lymphocytes in host defence. Learning objective: describe the importance of immunoglobulins in lung defence. Learning objective: appreciate the role of air way epithelial cells in lung defence. Defence mechanisms of the respiratory tract: Filtration and deposition of environmental pathogens and particulate matter in the upper air ways. Cough re ex. Mucociliary clearance. Innate and adaptive immune responses. Mucociliary clearance: Cilia Innate and adaptive immunity: Immunoglobulins: Glycoproteins found in serum and tissue uids. Produced in response to contact with immunogenic foreign molecules. Produced by plasma cells ( activated B cells ). Bind speci cally to the antigen that induced their formation. IgM: circulation. IgG: circulation and most tissues. IgA: skin mucosal membranes as a dimer; monomer when in circulation. IgE: mucosal membranes: gut, air way and skin. IgG: Monomer structure: four subclasses ( 1-4 ). Main antibody in serum and tissue uids. Extravascular. Opsonisation. IgA: Predominant antibody found in secretions. Important in mucosal immunity. Present on mucus membranes. Dimer joined by J chain. IgE: Monomer. Similar structure to IgG and also produced by plasma cells. Normally very low serum levels. Likely developed speci cally against parasite infections. Important in allergy. IgM: IgM- predominant antibody in the primary immune response. Pentameric structure in serum- large size limits transfer to tissues. Alveolar macrophages: Derived from cycling monocytes. When in tissue, they morph into macrophages. Scavenger cell; dispose of dead cells, cell debris, particular matter and invading microorganisms by phagocytosis. Sentinel cells sense bugs and release cytokines, which recruit neutrophils from the blood to the site of infection. Phagocytosis: 1. Bacterium attaches to the membrane. 2. Bacteria is ingested, forming a phagosome. 3. Phagosome fuses with a lysosome 4. Lysosome releases enzymes that digest the bacteria 5. Digested materials are released from the cel Immune response to viral respiratory infection: Allergy: