In vitro immunity of rat peritoneal macrophages to Candida albicans

Phagocytic, germ tube inducing and candidacidal activities were investigated in monolayers of peritoneal macrophages of rats. The phagocytic activities observed in macrophages of the healthy rats in the presence of normal serum, those in the presence of immune serum and of immunized rats in the presence of normal serum were 40%, 45.3% and 44.8% respectively. The percent of macrophages in which intracellular Candida formed germ tubes in the above three situations were 10, 9.59 and 10.19, respectively and the percent of intracellular Candida that formed germ tubes were 6.6, 3.7 and 4.1, respectively. The candidacidal activity observed in the above three sets of macrophages were 5.33%, 22.66% and 19.88%, respectively. Induction of germ tube in C. albicans in supplemented tissue culture medium containing normal serum was 15 per cent. These observations indicate that immunisation/sensitisation of individuals with C. albicans organisms does provide some degree of cell mediated immunity by activating macrophages. This may partly be due to the appearance of specific antibodies. It is likely that this type of immunity can be produced by subclinical infections during invasion by the commensal organism thus preventing further invasion establishment of infection and keeping the organism (C. albicans) in a state of commensalism. However, the degree of immunity so produced is so low that predisposing factors suppress it and allow establishment of infection.