Immunity

• What is an antigen?

  • Proteins on the cells surface that trigger an immune response from lymphocytes
• What are the 2 types of white blood cell?

  • Phagocytes- non specific
  • Lymphocytes- specific
• What happens in phagocytosis?

  • The phagocyte's receptors detect the chemical or antigen on the pathogen
  • The phagocyte changes shape to engulf the pathogen
  • The pathogen is contained in a vesicles called a phagosome
  • A lysosome in the phagocyte fuses with the phagosome to form a phagolysosome
  • The lysosome releases lysozyme enzymes which hydrolyse the pathogen
• What do T lymphocytes respond to?

  • Any foreign antigen presenting cell
  • Such as a macrophage form phagocytosis, a toxin, a transplant a virus, cancer and infected
• What is the cell mediated response (T lymphocytes)?

  • Helper T cells attach to foreign antigen presenting cells
  • Helper T cells then replicate by Mitosis
  • Helper T cells differentiate into memory cells or cytotoxic T cells
  • These also stimulate B lymphocytes and phagocytes
  • Cytotoxic T cells kill the entire foreign antigen presenting cell by perferating the membrane with perforin enzyme, the cell will then shrivel or burst with water causing lysis
• What is the humoral response (B lymphocytes)?

  • B cells present antibodies on their surface
  • Then the B cell collides with a Helper T cell presenting a complimentary antigen it initiates replication by mitosis (clonal expansion)
  • B cells then differentiate into plasma cells or memory B cells
  • Plasma cells make antibodies
  • Memory B cells can rapidly differentiate into plasma cells in future exposure
• How do antibodies work?

  • Antibodies don't directly kill pathogens, they mark them for destruction by phagocytes etc
• What is agglutination?

  • When antibodies bind to multiple antigens causing them to clump together and be located easier by phagocytes for phagocytosis
• What is active immunity?

  • When your body creates its own immunity when exposed to an antigen, such as vaccines, being exposed to a virus etc
• What is a vaccine?

  • A dead or weakened version of a pathogen
• How do vaccines work?

  • The body is exposed to the vaccine/pathogen
  • The B cells undergoes clonal expansion and undergoes mitosis
  • These cells differentiate into plasma cells to produce antibodies
  • They can also differentiate into B memory cells which can rapidly differentiate into plasma cells in future exposure
• What is direct monoclonal antibody therapy?

  • When antibodies are complimentary to only one type of attachment protein such as cancer cells
  • This prevents chemical binding and uncontrolled cell division of the
• What is indirect monoclonal antibody therapy?

  • When an antibody is only complimentary to 1 antigen but has a drug attached to it to only harm that cell Such as cancer
• What are the stages of the ELISA test?

  • First mobile antibody is complimentary to the antigen being tested for and has a colored dye attached
  • Second antibody is immobile and complimentary to the antigen aswell so when the antigen binds it brings the first antibody with it, this causes that line of dye on a test to confirm positive test for the antigen
  • The third antibody is immobile and complimentary to JUST the first antibody, which causes the line of dye to prove the test worked becsude the first antibody moved whether positive or negative