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HSS1100 Lecture 2.docx

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University of Ottawa
Health Sciences
William Yan

Lecture 2 Slide 1: -immunity: how a host finds ways to protect itself from pathogens through immune response -very complex system -there are 2 types of immunity: 1) non-specific (innate) immunity 2) specific (adaptive, acquired) immunity -both are of equal importance Slide 2: 1) Non-Specific (Innate) Immunity -blocks out everything (i.e.: physical barriers) -doesn't care whether the body is invaded by bacteria, viruses, etc. -the immune system detects foreign bodies regardless of pathogenicity Examples a) Skin (Intact Skin) -is an effective mechanical barrier (find out why) b) Mucous Membrane -cilia sweep particles (effective for most bacteria) -e.g.: cystic fibrosis patients are very susceptible to infection due to their disease -bacteria must be able to stick to the lungs in order to be successful -lysozymes are anti-bacterial enzymes that break down cell walls -pH: bacteria prefer moist, alkaline pH c) Iron-Binding Proteins -most body function is assisted by enzymes which may require heavy metals (i.e.: Fe) -transferrin / lactoferrin round up iron for use by enzymes -iron binding proteins protect against bacteria by competing for iron present in the system d) Phagocytosis - PMN = polymorphonuclear white blood cells -these are cells are produced by the immune system to target foreign bodies and engulf them -these cells are the 1st line of defense (in a healthy individual) -cells are always present and ready -cells are constantly in circulation e) Complement -involves a cascade of proteins -reacts non-specifically to foreign bodies Slide 3: 2) Specific Immunity -most research deals with specific immunity -targets specific pathogens when activated -is dependent on previous exposure -involves the humoral and the cell-mediated system Where do immune cells come from? -for the humoral system: -cells originate from B cells which produce different anti-bodies -for the cell-mediated system -the thymus produces T-cells -HIV attacks T-cells which makes the patient vulnerable What is the difference between innate immunity and adaptive immunity? –Innate: protects against ANY invader, does not discriminate –Adaptive: directed against one type of invader, dependant on past exposure Slide 5: a) Humoral Immunity -the key are anti-bodies (not the same as anti-biotics) -anti-bodies are a class of proteins made by the immune system -circulating anti-bodies are key -anti-bodies involve immunoglobulins (proteins) -no 2 anti-bodies are exactly the same when produced by B-cells -anti-bodies look for something to bind to in order to create a complex -recognize anti-gens -anti-gens are anything that is not part of the body (foreign entity) -can be proteins, saccharides, glycoproteins, lipoproteins, etc. -proteins are usually the strongest / most stimulating anti-gen -anti-gens are anything / any substance that triggers an immune response Slide 7: -an anti-body contains a variable region (the prong in the Y-shaped antibody) and a constant region -for an anti-body to bind to an antigen, the receptors must match at the binding site Slide 8: -the variable sites can hook up to different bacteria -this clumps bacteria together due to the cross-linking -this slows down growth of bacteria so that they can no longer function -it takes time to eventually kill the bacteria -clumping / cross-linking takes time Slide 10: -anti-body / antigen lab uses include: -blood tests (i.e.: white precipitates indicate agglutination) -helpful to identify bacteria Slide 11: -the N-terminus / binding site of the variable region determines the specificity Slide 12: -5 classes of immunoglobulins: 1) IgG -1 unit of the basic structure (Y structure) -the only class that has the ability to cross placenta and protect babies -the "maternal anti-body" 2) IgD -similar to IgG 3) IgA -found in body fluids -more powerful than IgA and IgD -is a dimer ( 2 basic subunits of the Y structure) -has 4 prongs and is therefore more effective in cross-linking and causing more clumping 4) IgM -5 subunits and 10 prongs -very efficient -involved in one of the earliest immune responses 5) IgE -associated with allergies / hypersensitivity -may be involved in protection with parasites Slide 14: Primary Response -involved in what happens when you get exposed to a foreign organism for the first time -both non-specific / specific responses are activated -the non-specific response is activated first -if bacteria remains, the specific response (i.e.: B-cells) are activated -Clonal Selection Theory -as you grow older, B-lymphocytes produce different types of B-cells (where each one is slightly different) -each antigen triggers 1 specific B-cell (the one with the best fitting anti-body) -once the particular B-cell is activated, the particular Ab is mass-produced -the primary response is not instantaneous -it takes time to produce Ab (this is known as the latent period) -it takes 21 days before blood level reaches a maximum -we may experience symptoms until this time -once the crisis is over, there is a feedback mechanism -the production of the particular Ab returns close to the original (but always more than the original) -overall, the primary response is specific, has a latent period, and is complicated Secondary Response -once the B-cell has been stimulated, it is primed -when you get exposed to an organism that carries the same antigen, the primed B-cell is ready to react right away (i.e.: there is no latent period) -the secondary response is much quicker and efficient -we are unlikely to see symptoms from the exact same pathogen -a fl
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