Host defence mechanisms: evaluation and roles of acquired defects and immunotherapy.

The development of an infectious process is a result of the interaction of the three determinants of infection: the infecting organism, the local site of infection and systemic host defences. Interaction of the various components is important in an understanding of the development of sepsis. Acquired defects of host defence mechanisms are attributable to a variety of factors and can be both the cause and the result of sepsis. The burn injury illustrates alterations in host defence and the interaction of the determinants of sepsis. Methods of evaluating the components of host defence are available, though sometimes difficult; in the future, evaluation of the effect of one component on another will become clinically feasible, allowing more complete assessment of acquired defects. Immunotherapy is not yet widely available; however, definition of the acquired defects of host defence mechanisms in surgical patients may eventually lead to introduction of effective treatment.