ABSTRACT
We have investigated the possibility that proteinases released by Candida albicans participate in the early killing of three types of mice peritoneal macrophage (resident, thioglycollate-elicited, or Con-A-activated)in vitro. Phagocytic assays were performed by incubation of macrophages and C. albicans together at a 1:10 ratio for 30 min at 37 grade C in RPMI medium buffered to pH 7.0 with 12 mM Hepes without serum. With no albumin added to the medium, the medium, the macrophages were 85% to 100% damaged and unviable, to a greater extent than expected from the proportion of phagocytic cells containing germ tubes. When 10 mg/ml of albumin was added to the medium, however, 90% of the macrophages remained viable for the 2 hours of the phagocytic assay, suggesting that albumin may have acted as a substrate for or inhibitor of proteinases released by C. albicans, thereby protecting the macrophage from the proteolytic action of the proteinases. The phagocytosis of IgG-coacted erythrocytes was reduced to 43% when IgG was preincubated with the supernatant from C. albicans cultures, but the addition of 10 mg/ml albuumin or of 5 ug/ml pepstatin (an inhibitor of C. albicans acid proteinases) to the same supernatans prevented the effect on phagocytosis of IgG-coated erythrocytes. These results suggest that proteinases released from C. albicans are involved in the early killing of macrophages