Adaptive Immunity to Bacteria

• The adaptive and innate responses work together to destroy bacteria

• The adaptive response ensures the innate response is carried out efficiently

Humoral

• Complement activation of the classical pathway
  • Production of IgM and IgG makes the complement system more efficient

Cell-Mediated

• Help for macrophages
  • IgG production (T-helper type II cells and B cells) which improves phagocytosis by opsonisation
  • Infected macrophages are rescued by T-helper type I cells when phagocytosis and digestion mechanisms fail to eliminate the pathogen

Extracellular Infection

• Complement and phagocytosis

• B cell and T helper type II cell stimulation

• Production of IgM which activates the classical cascade

• Class switching of IgM to IgG which is a good opsonin and targets bacterial Fcγ receptor expressed by macrophages and neutrophils

Vesicular Infection

• The infected macrophage secretes IL-12

• IL-12 stimulates T-helper type I cells which release IFN-γ

• IFN-γ triggers the macrophages to kill the pathogens inside