Effect on parasite eradication of Pneumocystis carinii-specific antibodiesproduced in the presence or absence of CD4(+) alpha beta T lymphocytes

The contribution of specific antibodies (Ab) to successful clearance of Pne umocystis carinii from host pulmonary tissues has received increasing atten tion. Sera collected from diseased recombinase-activating gene (RAG)-1(-/-) , TCR beta x delta(-/-), TCR beta(-/-) and A beta(-/-) mutants as well as f rom aerogenic parasite-exposed (aero) and intranasally (i.n.) infected C57B L/6 mice were transferred to RAG-1(-/-) mutants inoculated with freshly iso lated parasites. All sera, except for RAG-1(-/-) serum, contained P. carini i-specific Ab of varying isotype concentrations. Four weeks after serum tre atment pulmonary parasite numbers were reduced slightly by A beta(-/-) and C57BL/6-aero sera, and markedly by TCR beta(-/-) and G57BL/6-i.n. sera. Our data reveal: (1) T cells are essential, and CD4(+) T cells are important f or formation of protective Ab; (2) at least in the absence of alpha beta T cells, gamma delta T cells provide help for protective Ab. In vitro treatme nt of bronchoalveolar lavage cells with the different sera largely led to c omparable results. Opsonizing Ab impeding parasite attachment to host cells , as well as Ab possibly neutralizing parasite-secreted products were impli cated; Furthermore, serum components other than Ab appear to participate in resistance to fungal manifestation.