Schistosoma japonicum: Highly irradiated cercariae as a test for specific immunity in rhesus monkeys

Abstract A knowledge of the prechallenge state of immunity to schistosomes in immunized hosts is important for the study of immunoprophylaxis. In rhesus monkeys immunized with highly X-irradiated Schistosoma japonicum cercariae, the state of immunity can be determined by studying the lesions in skin which has been biopsied after a test inoculation with cercariae exposed to 48,000 R. If eosinophilic vesicles or pustules in the dermis are found at 12 hr, and if neither schistosomula nor giant cells are encountered on Day 6, the monkey may be regarded as having acquired a solid immunity. This test has been verified in three monkeys having a strong acquired resistance to schistosomes and appears to be harmless, because the cercariae used in the test die in the skin without involvement of other organs.