The mechanism(s) by which lymphokine-activated peritoneal macrophages kill Blastomyces dermatitidis was studied. Resident peritoneal macrophages from BALB/cByJ mice, when treated overnight with lymph node cells plus concanavalin A, supernatants from concanavalin A-stimulated spleen cells, or recombinant gamma interferon, were then able to kill a virulent B. dermatitidis isolate (ATCC 26199) (at levels of 25% +/- 4%, 28% +/- 8%, and 21% +/- 5%, respectively). Killing was not significantly decreased or enhanced in the presence of superoxide dismutase (450 U/ml), catalase (20,000 U/ml), dimethyl sulfoxide (300 mM), or azide (1 mM). Viable B. dermatitidis elicited a brisk oxidative burst and superoxide anion production in activated macrophages as measured by lucigenin-enhanced chemiluminescence, e.g., 10(4) cpm. However, these responses were not significantly different from those of control macrophages. Luminol-enhanced chemiluminescence responses by activated or control macrophages were meager (less than or equal to 10(2) cpm). These results indicate that activated macrophages kill B. dermatitidis by a mechanism(s) independent of products of the oxidative burst.