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Lecture 5

WEEK 5.docx

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Queen's University
BIOL 103
Virginia K Walker

WEEK 5: Role of Natural Killer Cells -NK cells also kill virus-infected and cancer cells by secreting toxic chem. -recognizes general features on the surface of affected cells--> nonspecific immunity -NK cells can be linked to target cells by antibodies IMMUNE TOLERANCE -body distinguishes b/w self and non-self components 1. during early development in vertebrates, T-cells are exposed to a wide variety of self proteins in the thymus -T-cells w/ receptors that bind to self proteins are destroyed via apoptosis-- >clonal deletion 2. clonal inactivation: occurs outside the thymus -causes potentially self-reacting T-cells to become nonresponsive -similar process w/ B-cells -autoimmune disease: when these defenses fail and the body attacks itself -humoral and cell-mediated attacks are directed against the body's own cells + tissues -MS: myelin attacked -Myasthenia Gravis: receptors for acetylcholine on skeletal muscle cells attacked -Rheumatoid arthritis: joints are damaged -Type 1 Diabetes Mellitus: islets of langerhans (produces insulin in pancreas) attacked IMMUNOLOGICAL MEMORY Primary Immune Response: to an initial exposure to an antigen Secondary Immune Response: any subsequent infection by the same pathogen -produces an immediate and heightened production of additional specific antibodies against that antigen -for humoral immunity: secondary response occurs more quickly, is stronger, and lasts longer b/c memory B-cells that had been produced in response to initial antigen exposure are quickly stimulated to multiply and differentiate into lots of plasma cells -->produced plasma cells produce lots of specific antibodies -explains why we are able to fight off many illnesses to which we have been previously exposed: Active immunity -->basis for vaccinations and immunizations: small amounts of living or dead microbes, toxins, or harmless antigen molecules injected into body to trigger primary immune response (production of memory B-cells) -Passive immunity: protection against disease through the direct transfer of antibodies from one individual to another -->occurs naturally -->eg. IgG crosses mammalian placenta to protect a fetus from various pathogens -->eg. when a newborn mammal receives antibodies from breast milk -->eg. artificially injecting antibodies for hepatitis -->since antibodies have a limited life
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