Effects of particulate beta-1,3 glucan on human, rat, and guinea pig complement activity.

Particulate glucan, a beta-1,3-linked polyglucose derived from Saccharomyces cerevisiae, has been demonstrated to have a wide range of immunopotentiating effects. Glucan administration is associated with the modification of a variety of experimentally induced infectious disease states as well as the inhibition of growth of implantable and spontaneous tumors. The present study was designed to evaluate the effect of glucan upon activation of the complement system in rats and guinea pigs. Additional studies were performed to determine the in vitro activating effect of glucan and zymosan on complement activity of human serum. Glucan activated both the classical pathway of normal human sera and the alternate pathways in C2hu-deficient sera in vitro releasing anaphylatoxins such as C3a. The intravenous injection of glucan activated the alternate pathway of guinea pig plasma. The influence of glucan on complement depletion induced by cobra venom factor (CVF) was also ascertained. Complement activation by glucan may contribute, in part, to the enhanced resistance of the host against tumor growth as well as infectious episodes.