Regulation of the human T-cell response toSchistosoma japonicum egg antigen by concomitant cellular and humoral mechanisms in vitro

Serum-mediated regulation of T-cell responses specific for soluble egg antigen (SEA) ofSchistosoma japonicum was tested in human hosts. When we added autologous serum to SEA-specific human T-cell lines (CD3+, 4+, 8–), we observed suppression of T-cell proliferation, and this suppressive activity was detected in the immunoglobulin-G2 (IgG₂) subclass. Suppression was dose-dependent and antigen-specific. T-cell proliferation induced by only one SEA fraction of >18 kDa was modulated in the presence of 100 g/ml autologous as well as allogeneic infected IgG₂. This SEA fractiondriven proliferation was also regulated by suppressor T-cells through distinct suppressive mechanisms. Our results suggest that T-cell responses to a particular component(s) of SEA are strictly regulated through both cellular and humoral mechanisms in human chronicS. japonicum infection.