Effect of T-cell transfer on Pneumocystis carinii infection in nude mice.

The effect of transfer of spleen lymphocytes from euthymic heterozygote littermates (nu/+) or rabbit antiserum on Pneumocystis carinii (P. carinii) infection in nude (nu/nu) mice was investigated. After intravenous administration of nu/+ spleen T-cells, the number of cysts in the lung of previously infected mice was markedly decreased at day 14 and further at day 30. Intense cellular reactions were seen at day 14 and subsided lesions at day 30. Increased IgG antibody titers were observed at days 14 and 30. Multiple treatments with immune rabbit serum after infection were not effective for reducing the cyst number in the lung, neither enhanced cellular reaction, while the immune serum administered prior to infection prolonged the survival time. The results indicated an important role of T-cell mediated immunity for the resistance to P. carinii infection in mice.