Nude mouse: a new experimental model for Pneumocystis carinii infection.

Experimental infection with both human- and rat-derived Pneumocystis carinii has been produced in nude mice by intrapulmonary injection of lung homogenates that contained P. carinii and by environmental transmission. Most infected mice did not appear ill, and their lungs exhibited a mild and nonspecific inflammatory response. Thus, P. carinii can be transmitted from one animal species to another, and this result suggests that a defect in thymic-dependent lymphocytes is important in the development of the infection. Experimental work with P. carinii in the nude mouse should be performed in isolators because of the communicability of the organism.