Fungicidal activity of murine broncho-alveolar macrophages against Blastomyces dermatitidis

The fungicidal activity of murine broncho-alveolar macrophages (BAM) against the yeast form of a virulent strain of Blastomyces dermatitidis was studied in the small-volume wells of a Terasaki plate. In a 4-h fungicidal assay, significant killing (16-33%) of the fungus by unstimulated BAM was demonstrated with BAM from normal mice and from mice rendered immune to lethal infection with B. dermatitidis. No significant differences between the activity of BAM from these two sources could be identified. Addition of 10% autologous normal or immune serum did not augment the macrophage fungicidal activity. Simultaneous experiments with peritoneal macrophages (PM) also gave reproducible killing of the yeast form in the wells of the Terasaki plate, but in the larger wells of microtitration plates, PM showed no significant fungicidal activity. On the other hand, BAM had similar fungicidal activity against B. dermatitidis in Terasaki and microtitration-plate wells. The modest fungicidal activity of BAM from immune mice against B. dermatitidis suggests that the resistance of immune mice to respiratory challenge is likely to be based on some augmentation of this first line of defence.