Processes

• Phagocytes


  1. Neutrophils - produced in the bone marrow -innate and secrete cytokines to attract phagocytes. Multilobed nucleus and grainy.
  2. Macrophages - produced in the bone marrow - innate
  3. Monocytes - Kidney shaped nucleus
• Lymphocytes


  Have large nucleuses and smaller than phagocytes.

  1. T cells - Mature in the thymus gland. Helper, Killer, Regulatory, Memory. Cell mediated immune response.
  2. B cells - Mature in bone marrow. Plasma and Memory. Humoral immune response.
• Phagocytosis - non specific

  1. Chemicals attract the phagocyte to the pathogen.
  2. Phagocytes recognises the pathogen as a 'non-self' cell
  3. Phagocyte engulfs the pathogen by endocytosis and is surrounded by a vacule - Phagosome.
  4. Phagosome combines with lysosome containing digestive enzymes forming a phagolysosome.
  5. Digestive enzymes break down the pathogen and waste is removed by exocytosis.
• Phagocytosis - Specific


  • Phagocytosis is done by a macrophage
  • Antigens from the broken down pathogen bind to maceophage antigens forming a - Histocompatibility complex (MHC)
  • Display antigens on the plasma membrane and becomes an APC - Antigen presenting cell.
• Specific immune response


  1. Antigen from pathogen or APC are present
  2. Detected by

  • T lymphocytes - cell mediated
  • B lymphocytes - humoral
• Cell mediated response


  • APC has antigens complemetry to receptor on t helper cell which stimulates the immune response - Colonal selection
  • Cloning by mitosis of the T cell and then differentiation into different t cells. - T helper, T regulator, T killer cells. - Colonal expansion and differentiation.
• Humoral response


  • In response to pathogens
  • Activated T helper cells bind to pathogen receptors on b cells - colonal selection
  • Activated T cell release interleukins which activate other b cells.
  • B cells rapidly divide by mitosis into - B plasma cells and B memory cells. - Colonal expansion.
  • Plasma cells produce specific and complementary antibodies which bind to the antigens, disabling them.
• Secondary response


  If the body is infected by the same pathogen again B memory cells rapidly divide into B plasma cells

  • Much faster response as primary response is skipped.