Comparison of corticosteroid- and L3T4+ antibody-immunosuppressed mouse models of Pneumocystis carinii pneumonia for evaluation of drugs and leukocytes.

An immunologically immunosuppressed mouse model of Pneumocystis carinii pneumonia using antibody developed by Dialynas et al. (Immunol. Rev. 74:29-55, 1983) directed to L3T4+ T cells (referred to as L3T4+ antibody) was compared with a corticosteroid-immunosuppressed mouse model. Corticosteroid- or L3T4+ antibody-immunosuppressed BALB/c mice transtracheally inoculated with P. carinii developed severe infections within 5 weeks after inoculation and responded to treatments with an echinocandin B analog, LY302146, or trimethoprim plus sulfamethoxazole so that they had decreased numbers of P. carinii cysts and trophozoites. LY302146 appeared to be more effective in L3T4+ antibody-immunosuppressed mice than in dexamethasone-immunosuppressed mice. Leukocyte populations in lungs of both mouse models during development of infection and during treatment were compared by using immune cell-specific staining. Lungs of L3T4+ antibody-immunosuppressed mice had many more cells detected with pan-B antibody and pan-T antibody than dexamethasone-immunosuppressed mice and the lungs of successfully treated mice had about the same numbers of macrophages as those of nonimmunosuppressed uninfected mice. The immunologically immunosuppressed model will allow study of cytokines and other immune modulators alone and in combination with drugs.