communicable diseases + the immune system

• viruses

  • smaller than bacteria, no cell structure
  • entirely dependent on their host to survive
  • HIV -
• how are pathogens digested

  phagocytes engulf pathogens into a phagosome, which fuses with a lysosome - enzymes digest the pathogen
• clonal selection

  activation of the correct B or T lymphocyte with a complementary receptor
• clonal expansion

  mitotic division of selected T-cell to make clones