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SIU BIOL 200B - Immune System

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BIOL 200B 1st Edition Lecture 20 Chapter 51 Immune System I. PathogensII. Immune system a. Innate immunityb. Adaptive immunityIII. Immune responses a. Humoral b. Cell-mediatedIV. AllergensImmune System Pathogens – agents causing disease; bacteria, fungi, virusesImmune system – recognizes foreign bodies and responds with proper production of immune cells and protein 1. Barrier defenses: skin, mucous lined passages, waxy secretion, lysosome secretion 2. Innate immunity (nonspecific) - All animals - Recognition of broad range of pathogens - Few nonspecific receptors- Rapid response- Barrier defenses and internal defenses 3. Adaptive (specific)- Vertebrates - Specific pathogens - Broad range- Slower- Humoral and cell-mediated response Pattern recognition: distinguish “self” cells from pathogens - antigens – molecules immune system recognizes as non-self; on pathogen surface - responses vary with pathogen - epitopes – differing regions on antigen molecule These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Innate immune response - Leukocytes – “infection police”- Present form birth- Involves nonspecific responses - Pathogens entering body subject to phagocytosis - Mast cells, neutrophils, macrophages Inflammatory innate immune response 1. Pathogen enters wound2. Alarm chemicals recruit immune cells3. Neutrophils destroy pathogens by phagocytosis 4. Macrophages induce fever and destroy pathogens 5. Platelets seal wound, allow for healing Adaptive immune response - Lymphocytes – “infection SWAT team”- B cells – produce antibodies (attack proteins); bone marrow- T cells – diverse functions; thymus - B and T cells activated in spleen and lymph nodes; use lots of protein synthesis- Distinguishing “self” from “nonself”: MHC (major histocompatibility complex) o Self markers on surface of every cello Lymphocytes that react with self markers are eliminated during maturation in bone marrow and thymus o MHC molecules in infected cells bind and transport antigen fragments to cell surface; process called antigen presentation o T cell can then bind both the antigen fragment and MHC molecule - 2 branches of adaptive immunity: humoral and cell-mediated immune responses; triggered by helper T cells 1. Humoral immune response: antibodies from B cells help neutralize eliminate toxins and pathogens in blood and lymph - B cells have surface receptors proteins that recognize antigens - Helper T cells activate B cells bound to antigen - Cytokines cause B cell to clone itself by mitosis - Cloned B cells secrete free floating receptors called antibodies2. Cell-mediated immune response: specialized cytotoxic T cells destroy affected host cells - Cytotoxic T cells bind MHC molecules displaying viral fragments on infected host cell surface- Limits spread of infection by preventing new generations of virus particles from maturing Huge diversity of B and T cell receptors - Different branches of antibody proteins - Gene recombination when lymphocyte is produced; produces new antibodies Clonal Selection Theory Adaptive system “remembers” past infections: some B and T cell clones persist for long time – memory cells (cause secondary immune response)Allergies – hypersensitive immune response to antigens called allergens Hygiene hypothesis of allergies: inverse correlation of allergies with parasite


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