Pulmonary cryptococcosis in the rat.

We evaluated a rat model of pulmonary cryptococcosis. Rats immunized subcutaneously with cryptococcal antigen developed peritoneal but not pulmonary macrophage migration inhibition factor (MIF) to cryptococcal cell extract antigens. They did not develop MIF to capsular polysaccharide antigens. Conversely, when rats were immunized subcutaneously with heat-killed cryptococcus neoformans, migration inhibition factor was detected in alveolar but not in peritoneal macrophages. Finally, rats given viable cryptococci subcutaneously developed both pulmonary and extrapulmonary cell-mediated immune responses. When viable C. neoformans were administered directly into bronchi of the right lung, immunologically intact rats developed hard nodular lesions in the ipsilateral lung. These contained caseous centers with numerous cryptococci seen on histologic examination. Over the course of 9 months, the lesions shrunk and disappeared. In contrast, congenitally athymic (nude) rats developed progressive cryptococcosis with widespread dissemination. The rat appears to be a useful model for study of pulmonary cryptococcosis.