The septic burned patient: a model for studying the role of complement and immunoglobulins in opsonization of opportunist micro-organisms.

Studies were performed to determine the effects of septicemia on complement levels and activities and opsonic function in septic and nonseptic burned patients. None of the nonseptic burned patients had consumption of classical pathway activity during their clinical course. Patients who did not survive septicemia had consumption of all of the classical complement components (C1-C5) prior to and during their septic episodes. Patients who survived septicemia had multiple patterns of classical complement pathway consumption. In these patients, classical pathway activity was restored to normal following the last positive blood culture. Alternative complement pathway consumption was demonstrated in only one of the septic burned patients, as evidenced by decreased factor B and C3b INA levels and decreased C3 and C5 conversion in sera treated with 10 mM ethylene glycol tetraacetic acid and 10 mM MgCl(2) (MgEGTA) and in untreated sera. In all of the other septic patients and in the nonseptic patients, reduction in C3 and C5 conversion in MgEGTA sera and untreated sera was not associated with decrease in factor B or C3b INA. Reduction in complement levels and activities did not reduce the ability of the patients' sera to promote phagocytosis and intracellular killing of their infecting micro-organisms by normal human peripheral polymorphonuclear leukocytes. The results indicate that measurement of classical pathway activity in burned patients can be used as a diagnostic tool for predicting the severity of septic episodes and for monitoring recovery. In addition, the observation that complement consumption did not reduce the opsonic capacity of the patients' sera for their infecting micro-organisms suggests that current concepts regarding the role of immunoglobulins and complement in opsonization of opportunist micro-organisms require re-evaluation.