The Role of BCG/PPD‐Activated Macrophages in Resistance against Systemic Candidiasis in Mice

The main conclusions of this study are that BCG/PPD‐activated macrophages, in contrast to macrophages from control mice, exhibit an increased PMA‐induced production of H 2 O 2 . kill about one‐third of the phagocytosed Candida albicans , and cause more than 5O% inhibition of the intracellular formation of germ tubes by C albicans . Peritoneal macrophages from mice that were colonized post‐natally with C. albicans do not show increased produciion of H 2 O 2 : upon stimulation with PMA and the intracellular outgrowth of germ tubes is inhibited to only a limited degree. These macrophages are capable of killing about 2O% of the ingested C, albicans . In vivo, the number of Candida in the kidney, spleen and liver after intravenous injection of Candida albicans is significantly lower in BCG‐treated mice than in control mice. Post‐natal colonization with C. albicans has only a limited effect on the outgrowth of intravenously injected C albicans the spleen and liver but does not influence growth in the kidney. These results indicate that acquired immunity against a systemic Candida infection involves both oxidative and nonoxidative mechanisms of intracellular killing and that these mechanisms may have different effects on the yeast and hyphal forms of C. albicans .