A&P: CH.21 [Immune System]

    Cards (81)

    • immunity: resistance to disease
    • innate immunity: nonspecific, generalized defense mechanisms that are present at birth; fast
      • surface barriers (skin etc.)
      • internal defenses (phagocytes, etc)
    • adaptive (acquired) immunity: specific defenses against pathogens acquired during life; slower
      • B cells (humoral immunity)
      • T cells (cellular immunity)
    • inflammation is the body's response to injury or infection; it involves redness, swelling, heat, pain, and loss of function
    • innate and adaptive defense similarities
      • same defensive molecules
      • specific pathways to target certain foreign substances
      • proteins released during innate responses alert cells of adaptive system
    • the skin provides an initial barrier to entry by microorganisms; keratin is also resistant to most weak acids and bases and to bacterial enzymes and toxins
    • skin also has protective chemicals like
      • acid: acid mantle which inhibits bacterial growth
      • enzymes: lysosomes
      • mucin: traps microorganisms
      • defensins: antimicrobial peptides
      • others: lipids in sebum and dermcidin in eccrine sweat toxic to bacteria
    • respiratory tract mucosae have structural modifications to prevent pathogens from entering
    • internal innate defenses include phagocytes, natural killer cells, antimicrobial proteins and fever
    • neutrophils are short-lived white blood cells that engulf and digest bacteria
    • macrophages are large white blood cells that can ingest and destroy many types of pathogens
    • natural killer (NK) cells destroy virus infected host cells and cancerous cells
    • opsonization: pathogen is coated with opsonins to accelerate phagocytosis
    • NK cells eliminated cancer sells by detecting general abnormalities such as lack of "self" cell-surface proteins called MHC
    • inflammatory response benefits
      • prevents spread of damaging agents to nearby tissues
      • disposes of cell debris and pathogens
      • alerts adaptive immune system
      • sets stage for repair
    • histamine: a compound which is released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.
    • toll-like receptors: a type of receptor that recognizes pathogen-associated molecular patterns; releases inflammatory chemicals called cytokines
    • hyperemia occurs when the blood vessels dilate and the blood flow increases; responsible for redness and heat during inflammation
    • exudate: a mass of cells and fluid that has seeped out of blood vessels or an organ, especially in inflammation; contributes to pain and swelling
    • phagocytes mobilization
      1. leukocytosis: neutrophils enter blood from bone marrow
      2. margination: neutrophils cling to capillary wall
      3. diapedesis: neutrophils flatten and squeeze out of capillaries
      4. chemotaxis: neutrophils follow chemical trail from inflamed site
    • antimicrobial proteins enhance innate defenses by attacking microorganisms by directly hindering ability to reproduce; most important are interferons and complement proteins
    • interferons: help protect cells that have not yet been infected by viruses; cancer fighting cells like macrophages and NK cells
    • IFN alpha and beta have antiviral effects and activate NK cells
    • IFN gamma "immune interferon" secreted by lymphocytes and activated macrophages
    • IFNs can treat hepatitis C, genital warts, multiple sclerosis and hairy cell leukemia
    • complement system has three functions: opsonize (coat) pathogen so phagocyte will engulf it, lyse (burst open) pathogen membrane, attract immune cells to the area
    • complement is a nonspecific defensive mech. but it enhances both innate and adaptive defenses
    • classical pathway: antibodies bind to an antigen on a microbe's surface which activates the first enzyme in the cascade; adaptive immune system
    • lectin pathway: lectins bind to carbohydrates on the surface of pathogen; innate immune system
    • alternative pathway: activated spontaneously when other complement factors interact; lack complement activation inhibitors our own cell have
    • classical, lectin, alternative pathway converge at C3, which cleaves into C3a and C3b -> enhances inflammation, promotes phagocytosis, cause cell lysis
    • MAC (membrane attack complex): a complex of enzymes that digests the bacterial cell wall leading to cell lysis
    • C3b molecules are responsible for opsonization of bacteria and phagocytosis
    • leukocytes and macrophages exposed to foreign substances release pyrogens that act on clusters of neurons in the hypothalamus- leading to fever
    • fever is an adaptive response because it increases metabolic rate, slows growth of microbes, and stimulates production of antibodies
    • adaptive immune system: body's built-in specific defensive system that eliminates pathogens; must meet or be primed with an antigen
    • adaptive system amplifies inflammatory response and responsible for complement activation
    • AIDS and cancer appears when adaptive immune system is not working properly.
    • humoral immunity: antibodies present in body's fluids; produced by lymphocytes and bind to extracellular targets to inactivate them temporarily and mark them for destruction by phagocytes or complement
    • cellular immunity: lymphocytes themselves instead of antibodies defend body; cellular targets are parasite-infected tissues, cancer, foreign graft cells
      • direct: killing infected cells
      • indirect: release chemicals enhancing inflammatory responses
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