Experimental cutaneous leishmaniasis. 3. Effects of thymectomy on the course of infection of CBA mice with Leishmania tropica.

This paper describes the course of infection and the immunological response in thymus-deprived and normal CBA mice after intradermal inoculation with promastigotes of L. tropica. Infection of normal mice resulted in the development of a cutaneous ulcer healing within 12 weeks. As the infection progressed and the draining lymph nodes increased in weight, changes in the paracortical and follicular regions were accompanied by the development of delayed hypersensitivity and the production of antibodies detectable by immunofluorescence and a parasite agglutination test. Lesions in thymectomized irradiated mice healed more slowly and the draining lymph nodes were smaller than in normal mice. Follicular reactions were feeble and paracortical activity depressed. The most noticeable feature of these lymph nodes was a persistent and intense macrophage infiltration. Delayed hypersensitivity and antibodies detectable by immunofluorescence were correspondingly low; but parasite agglutinating antibody was not depressed. The course of infection and immunological response of a control group of sham thymectomized, irradiated mice resembled that of normal mice. These experiments indicate that thymus-dependent cell populations play an important role in the response of mice to infection with L. tropica.