Immunity

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  • Immunity
    • non-specific
      • mast cells
        • produce histamine
          • responsible for inflamation
            • as it makes capillary walls more permeable so more leukocytes can enter infected area
      • physical barriers
        • eg. skin, mucus
      • phagocytosis
        • phagocyte attracted infected area by chemical trail produced by non-self pathogens
          • phagocyte moves by chemotaxis process to pathogen
            • receptors on phagocyte cell surface membrane bind to pathogen
              • phagocyte membrane the forms vesicle around the pathogen called a phagosome thus engulfing it
                • phagosome fuses with lysosome in phagocyte to form phagolysosome
                  • lysosome contains digestive enzyme lysozyme which digests pathogen
                    • Neutrophiles then release fragments by process of exocytosis
                    • macrophages then associate pathogen's antigens with major histocompatibility complex (MHC) which is presented on cell surface
                      • now they are called an antigen presenting cell (APC)
                        • these then travel to lymphatic system to help stimulate specific response
    • specific
      • humoral
        • specific B lymphocyte binds to the MHC-antigen complex on APC or pathogen
          • B lymphocyte then divides by mitosis to produce...
            • memory B lymphocyte
              • for the secondary immune response
            • plasma cell
              • these only live for a few days but can produce up to 2000 specific antibodies a day
                • different antibodies have different effects on the different antigens they target
                  • agglutination = clumps the pathogen together so cannot enter self-cells and multiple pathogens can be engulfed by a single phagocyte
                  • opsonisation = antibodies coat the outside of the pathogen thus identifying it as non-self to phagocytes
                  • antitoxins = neutralise toxins produced by bacteria
                  • by lysis = pathogen destroyed by digestion and rupture of the membrane (for example by opening protien channels
      • cell mediated
        • specific helper T cells receptor (TCR) bind to antigen-MHC complex on APC with aid of CD4
          • helper T cell then...
            • divides by mitosis to produce another activated helper T cell and memory helper T cell
            • secretes cytokines
              • which activates specific cytotoxic T cell
                • cytotoxic  T cell then binds with the aid of CD8 to the pathogen's antigens
                  • then secretes perforin which perforates the pathogen's cell membrane
                    • causing lysis  causing the pathogen to undergo apoptosis
                • also divides by mitosis to produce activated cytotoxic T cell and memory cytotoxic T cell

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