HUMAN NEUTROPHIL-MEDIATED FUNGISTASIS AGAINST HISTOPLASMA-CAPSULATUM - LOCALIZATION OF FUNGISTATIC ACTIVITY TO THE AZUROPHIL GRANULES

Human neutrophils (PMN) demonstrated potent fungistatic activity again st Histoplasma capsulatum (Hc) yeasts in a sensitive microassay that q uantifies the growth of yeasts by the incorporation of [H-3]leucine. A t a PMN:yeast ratio of 1:2, PMN inhibited the growth of yeasts by 37%. Maximum inhibition of 85% to 95% was achieved at a PMN / yeast ratio of 10:1 to 50:1. Opsonization of the yeasts in fresh or heat-inactivat ed serum was required for PMN-mediated fungistasis, but ingestion of t he yeasts was not required. Recognition and phagocytosis of opsonized yeasts was via PMN complement receptor (CR) type 1 (CR1), CR3, and FcR III (CD16). PMN fungistatic activity was evident by 2 h, was maximum a t 24 h, and persisted up to 5 d. In contrast, yeasts multiplied within monocytes to a greater extent than in culture medium alone. PMN from three patients with chronic granulomatous disease (CGD) inhibited the growth of Hc yeasts by an average of 97%, compared with 86% in three n ormal controls. Furthermore, preincubation of PMN with the lysosomotro pic agent NH4Cl inhibited fungistatic activity in a concentration-depe ndent manner. Finally, experiments with subcellular fractions of PMN d emonstrated that the principal component of the fungistatic activity o f PMN was localized in the azurophil granules. These data demonstrate that human PMN possess potent fungistatic activity against Hc yeasts a nd further show that fungistasis is mediated by antimicrobial agents c ontained in the azurophil granules.