A monoclonal antibody to gamma interferon blocks augmentation of natural killer cell activity induced during systemic cryptococcosis.

These studies demonstrate that the cytotoxic activity of splenic natural killer (NK) cells is augmented in both nu/nu and nu/+ mice during systemic cryptococcosis. Both the kinetics and the regulation of NK cell activity differed in Cryptococcus neoformans-infected nu/nu and nu/+ mice. Greater augmentation was observed following challenge with 10(5) cells than with smaller inocula, and augmented NK cell activity was not always associated with enhanced control of systemic cryptococcosis. Infection with a nonencapsulated strain of C. neoformans induced an early but transient increase in splenic NK cell activity in nu/nu and nu/+ mice. Injection of capsular polysaccharide induced a transient augmentation of splenic NK cell activity in nu/+ mice but caused a persistent increase in splenic NK cell activity in nu/nu mice. In vivo treatment with monoclonal antibody to gamma interferon abrogated the augmentation of splenic NK cell activity induced during cryptococcal infections in both nu/nu and nu/+ mice and enhanced the susceptibility of nu/+ mice to C. neoformans to a greater extent than it did that of nu/nu mice. These results suggest that gamma interferon is an important mediator of resistance to C. neoformans.