Immunity

    Subdecks (5)

    Cards (92)

    • Defence mechanisms split into specific and non-specific
    • non-specific defence mechanisms are immediate and the same for all pathogens
    • specific defence mechanisms are slower and specific to each pathogen
    • Non-specific defence mechanisms include physical/chemical barriers and phagocytosis
    • Physical/ chemical barriers are the first line of defence
    • Phagocytosis is the second line of defence
    • specific defences include cell-mediated responses and humoral responses
    • cell mediated responses involve T lymphocytes
    • humoral responses involve B lymphocytes
    • cell mediated and humoral responses are part of the third line of defence
    • Ear's defence: cerumen inhibits bacteria growth
    • eye's defence: cleansed by tears which contain a chemical that inhibits bacteria growth
    • stomach's defence: stomach acid kills most pathogens
    • mouth's defence: saliva contains lysozymes (enzyme) that breaks down bacterial cell walls
    • skin's defence: keratinised outer layer prevents water loss, dead skin cells shed regularly, melanin pigment protects from UV radiation, sweat glands produce antimicrobial chemicals
    • urinary system's defence: urine is sterile due to urethra being short and narrow, kidneys have immune cells called macrophages that destroy pathogens
    • trachea and bronchi's defence: mucous layer traps microorganisms
    • vagina's defence: acidic secretion inhibits growth of pathogens
    • Phagocytosis is a non-specific immune response where white blood cells engulf and digest foreign particles
    • Steps of phagocytosis:
      1. adherence of microbe to phagocyte
      2. Phagocyte ingests microbe
      3. Formation of phagosome
      4. Phagosome fuses with lysosome
      5. Enzymes digest microbe
      6. Indigestible material forms a residual body
      7. Waste is discharged
    • Once a phagocyte has engulfed and digested an antigen, it can become an antigen presenting cell
    • Cells involved in the specific immune response are smaller white blood cells called T and B lymphocytes
    • Lymphocytes have a specific mode of action against infection and the response is specific to the pathogen
    • The specific immune response is triggered by the recognition of an antigen via specific, complimentary cell surface receptors
    • Antibodies are proteins produced by activated B cells
    • The specificity of an antibody depends on the antigen binding sites which have a unique tertiary structure
    • All antibodies have the same constant regions
    • Plasma cells are 'clones' of B cells
    • B cells bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes
    • B cells secrete antibodies specific to antigens that are also known as 'monoclonal antibodies'
    • The antigen-binding site matches the epitopes of antigens on the surface of the pathogen
    • Antibodies are made up of 4 long polypeptide chains
    • 2 of the polypeptide chains that make up an antibody are long and called 'heavy chains'. 2 are short and are called 'light chains'
    • The hinge region of an antibody allows movement so that the antigen binding site can be placed at different angles in order to bind to the antigens
    • Agglutination- clumping of antibodies to form a mass
    • An antibody has two binding sites and so can actually bind to 2 pathogens simultaneously
    • Phagocytes bind to the antibodies that are binded to the pathogens to engulf them
    • T helper cells stimulate cytotoxin T cells, B cells and phagocytes
    • T helper cells are essential in immunity and allow the activation of specific immune cells
    • Without T helper cells a person is immunodeficient