Immune response

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  • Immune response
    • Antigens
      • Proteins on surface of cells that generate an immune response when detected by the body
      • Used by immune system to identify pathogens, abnormal body cells, toxins and cells from other individuals of same species
    • 1: Phagocytes engulf pathogens
      • 1) Phagocyte recognises foreign antigens on pathogen
      • 2: Cytoplasm of phagocyte moves around pathogen, engulfing it
      • 3: Pathogen now contained in a phagocytic vacuole in cytoplasm of phagocyte
      • 4: Lysosome containing lysozymes fuses with phagocytic vacuole. Lysozymes break down pathogen
      • 5: Phagocyte presents pathogens antigens to activate other immune system cells
    • 2: Phagocytes activate T-cells
      • Type of white blood cell. Receptor proteins on surface- bind to complementary antigens with phagocytes
      • Activates T-cell.
      • Helper t cells release chemical signals that activate/stimulate phagocytes/ cytotoxic t cells which kill abnormal/foreign cells
      • Helper t cells also activate b cells which secrete antibodies
    • 3: B cells
      • Type of white blood cell. covered with antibodies- proteins which bind to antigen to form antigen-antibody complex.
      • Each b cell has different shaped antibody, so bind to different shaped antigen
      • 1) When antibody on surface of b cell  meets complementary antigen, they bind.
      • 2) With other substances from helper t cells this activates b cell- clonal selection
      • 3) Activated b cell divides into plasma cells
    • 4: Plasma cells
      • Plasma cells identical to b cells. Secrete antigen specific antibodies- monoclonal antibodies
      • Bind to antigens on surface of pathogen to form antigen-antibody complexes
      • Antibody has two binding sites- can bind to two pathogens at same time. Pathogens become clumped together- agglutination
      • Phagocytes bind to antibodies and phagocytose many pathogens at once.This leads to destruction of pathogens carrying this antigen


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