Interactions between human bronchoalveolar macrophages and Blastomyces dermatitidis conidia: demonstration of fungicidal and fungistatic effects.

The effects of human bronchoalveolar macrophages (BAMs) on Blastomyces dermatitidis conidia were investigated. Macrophage monolayers were incubated for 5 days with or without interferon (IFN)-gamma or macrophage colony-stimulating factor (M-CSF) before challenge with conidia for 48 h at 37 degrees C. Hyphal growth (germination) was inhibited 12% by resident BAMs (P < .05). In contrast, resident BAMs blocked conidial phase transition by 88% (P < .05). Intermediate forms, aggregates of large cells in clums (not conidia or yeasts by morphologic criteria), appeared after incubation with BAMs and grew into typical yeasts once removed from the BAMs. IFN-gamma and M-CSF inhibited the ability of BAMs to block phase transition but not germination. Human BAMs demonstrated fungicidal and fungistatic activity against B. dermatitidis conidia independent of reactive oxygen intermediates and had greater effects on phase transition than on germination. The phase transition-associated fungicidal and fungistatic activities of BAMs were inhibited by IFN-gamma and M-CSF.