primary immune responses

• activation of T helper cells 


  bacterium engulfed by macrophage

  macrophage becomes APC

  APC binds to T helper cell

  T helper cell activates and divides into T memory cells and T helper cells
• what is APC 


  antigen presenting cell
• clonal selection 


  antigen binds to B cell

  B cell becomes APC

  activated T helper cell bind to APC

  T helper cells produce cytokines that stimulate the B cell

  B cells divide into B memory and effector cells

  B effector cells differentiate into plasma cells

  plasma cells release antibodies
• role of T killer cells 


  bacterium infects host cell

  host cell becomes APC

  T killer cell binds to APC

  T killer cells divide into active and memory T killer cells

  active T killer cells bind to APC

  T killer cell release chemicals that destroy infected cell