Defects in phagocytic functions.

Phagocytic cells play a critical role in host defence against bacterial infections, often seen as frequent infectious episodes in patients with granulocytopenia, a quantitative phagocytic disorder encountered not infrequently in clinical practice, and in the more rare patients who have a clinically significant qualitative disorder, i.e., a normal number of phagocytes but defects in phagocyte function. In addition to infective agents, phagocytes can be activated by noninfectious structures such as immune complexes. In either case, phagocyte activation, also, inevitably results in destruction of the host's own tissues. Consequently, the degree of phagocyte activity is a double-edged sword: hypoactivity renders the host susceptible to infections while hyperactivity leads to undue phagocyte-mediated tissue injury. This review will discuss the physiology and qualitative defects, including hypoactivity, hyperactivity and inappropriate activation of phagocyte function, as well as the management of the patients.