Cell-mediated immunity to schistosomes. Evaluation of mechanisms operating against lung-stage parasites which might be exploited in a vaccine.

This report describes parallel studies examining T cell and cytokine responses to Schistosoma mansoni in mice and man. The prevalence of IFNg production amongst murine (C57BL/6) T cell lines and clones, plus good DTH reactivity by IFNg-secreting clones, highlights the predominance of the Th1 response in the pulmonary immunity characteristics of the murine irradiated vaccine model. In human studies, effects of anti-cytokine antibodies on the proliferation of PBMC from human patients to various soluble schistosome antigen preparations have been examined. Data suggest that both Th1 (against early antigens) and Th2 (against late antigens) responses are present. A role for IL-10 is highlighted in chronic intestinal, but not acute or chronic hepatosplenic patients, as a downregulator of responses which are associated with morbidity and are against late stage antigens.