The immunology of infection

When micro-organisms invade, conserved pattern recognition receptors activate innate defences including phagocytes, cytokines and complement followed by acquired immune responses mediated by T cells and B cells. Many pathogens have evolved specific mechanisms that enable them to evade host defences. An increasing number of individual human genes that influence the outcome of specific infections have been identified. Deficiency of specific components of the immune system (as a result of either genetic or acquired disorders) can predispose to characteristic patterns of infection. The immune response may also contribute to the pathogenesis of infectious disease as a result of excessive cytokine production or immune complex formation.