Effects of stimulation and suppression of cell-mediated immunity on experimental cryptococcosis.

A model of cryptococcosis was developed using intraperitoneal infections of guinea pigs. This model shared characteristics with cryptococcosis in humans and was used to study the effects of immunosuppression and immunostimulation on cryptococcosis. Female guniea pigs survived longer than males; perphaps this was related to a greater capacity of their monocytes to kill cryptococci. A brief course of cortisone shortened survival of females and resulted in depressed immune and inflammatory responses, which persisted long after cortisone was stopped. Stimulation of the immune response by treatment with cryptococci in Freund complete adjuvant improved survival in males. Preliminary studies indicated the usefulness of this model for the study of other potential immunostimulants, including immune lymphocytes, transfer factor prepared from immune lymphocytes, and levamisole. Overall, long-term survivors appeared to clear disseminated cryptococci from extraperitoneal sites including brain, rather than prevent dissemination of cryptococci from the peritoneal cavity. The quantity of the inflammatory response in infectious foci, rather than the ability of individual leukocytes to kill crytococci, may have determined the outcome of most infections.