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Transcript
Medical Microbiology Chapter 11 – Elements of Host Protective Responses Our Defense Systems Our body has 3 layers/walls of defense against pathogens and toxins • 1st = barriers • 2nd = innate responses • 3rd = antigen-specific immune responses My Analogy Barriers Barriers • Skin • Mucous membranes • Secretions – lactic acid and fatty acids (skin) – mucus: filter for respiratory system, etc. – Tears, lysozyme, stomach acid • Normal flora Innate Responses Responses – they are always present and ready to go. • Complement Proteins • Neutrophils and Macrophages • Natural Killer cells Innate Ag-specific Responses Must be produced after infection (usually takes 5-7 days) • Activated B-cells produce Antibodies • Activated T-cells attack and destroy infected cells and cancer cells Players in Defense Chemicals (allow communication between cells): • Cytokines – stimulate and regulate the immune response • Interferons – anti-viral proteins, stimulate immune response • Chemokines – involved with the inflammatory response – They lead to chemotaxis and activation Players in Defense Table 11-1 Cells (carry out the actual defense): • Table 11-2 and Figure 11-1 • Some are designated by CD “Clusters of Differentiation” • MHC I – found on all nucleated cells • MHC II – found on antigenpresenting cells (APCs) Players in Defense Blood cells of defense – Table 11-3 The Lymphatic System Functions: • Return tissue fluid to the blood stream – Why is this necessary? – Example (~30L out of capillaries, 27L in) • Fat transportation • Immunity – defense against pathogens and other foreign material Lymphatic Vessels Lymph capillaries – pick up interstitial fluid • lymph vessels – have one-way valves like the veins Lymph • Lymph is dumped back into the blood Figures from other text Lymphatic Vessels As the lymph travels back to the blood stream it passes through many lymph nodes Figures Lymph Nodes Function as filtering stations for the lymph Macrophages are in the lymph nodes • What do they do? B-cells and T-cells are also in the lymph nodes • Swollen lymph nodes Lymph Nodules and Tonsils Lymph nodules • No lymph filtering Tonsils are accumulations of lymph nodules • Function? – swollen tonsils are a sign of a throat infection • Figure Spleen The spleen is the filtering site for the blood • Dead RBCs • Figure