Studies on the immunological disturbance in murine schistosomiasis japonica from the viewpoint of the interleukin cascade reaction.

We examined the mechanisms of disturbed T-lymphocyte function that occurred during Schistosoma japonicum infection of BALB/c mice from the viewpoint of the interleukin cascade reaction. Each point of the interleukin cascade reaction was examined. First, IL-1 production by adherent peritoneal or spleen cells, as a source of macrophages, was normal or rather enhanced during the infection, the values being 100-180% of the control. Secondly, proliferative response to exogenous IL-1 of thymocytes from S. japonicum-infected mice progressively decreased during 3-7 weeks of infection. Thirdly, IL-2 production of S. japonicum-infected mice was significantly inhibited, even at 2 weeks of infection, and the activity was 10-20% of the control at 5-8 weeks of infection. Diminished IL-2 production was not caused by suppressive factors, such as PGE2 or suppressor macrophages, or a decrease in the number of IL-2 producing T cells. Finally, the response to exogenous IL-2 in S. japonicum-infected mice was suppressed markedly by 4 weeks of infection, and the responsiveness was reduced to 20% of the control at 8 weeks of infection. The mechanisms of disturbances in T-cell functions in S. japonicum-infected mice are discussed.