Immune responses to Schistosoma mansoni in rhesus monkeys with multiple chronic and early primary infections.

Immunological reactivity in 10 rhesus monkeys was monitored over a 22-week period. Cellular and humoral responses of three animals were studied after primary infection with Schistosoma mansoni. Two uninfected animals served as controls. Increased lymphocyte proliferative responsiveness to mitogens and adult worm antigen was evident during the prepatent period of the infection. Marked suppression of these responses occurred during the acute phase of the disease, but by weeks 9 and 11 the animals were again responsive to mitogens and antigen, respectively, and remained so throughout the remainder of the observation period. No antibody response to various cercarial, adult worm, and egg antigens could be detected until weeks 5 to 7, after which these responses also persisted. Comparison of the immunological reactivities of these animals with primary infection and those of five chronically infected immune animals indicated possible correlations between protective immunity and (i) strong Cercarienhüllenreaktion reactivity, and (ii) lymphocyte proliferative responsiveness to adult worm antigen.