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Schistosoma mansoni cercariae were used to infect CBA-J mice, a strain characterized by possessing a high level of NK cells. 4 days after infection with cercariae, the natural cytotoxic capacity of these mice, as measured by NK and ADCC, reached a peak level of enhancement significantly greater than that of uninfected controls. Infection by this parasite appears to activate natural cell-mediated immune defense systems. Further observation of the pattern of response of NK and ADCC effector cells to infection by cercariae may reveal important information regarding the inherent immunity to the schistosome infection.

Athymic nude mouse homozygotes (nu/nu) and the heterozygote nu/nu+ were injected intraperitoneally with 2 mg of cyclosporin-A (CS-A) twice, 72 and 1 h prior to analysis. We have found that in vivo administration of CS-A results in a significant suppression of natural killer (NK) cell and antibody-dependent cell-mediated cytotoxic (ADCC) activity which probably play an important role in tumor and graft rejection. T cells were also suppressed, in contrast, B cells were found to be immunocompetent as determined by cell proliferation and antibody-forming capacity in response to mitogens and antigens. The identity of cells mediating NK cell and ADCC activity and its relationship to T lymphocytes are also discussed.