HLA-DQ-controlled T cell response to soluble egg antigen of Schistosoma japonicum in humans.

We analysed regulatory mechanisms of the human T cell response to soluble egg antigen (SEA) of Schistosoma japonicum in vitro. SEA is a crude antigen mixture containing numerous epitopes. We obtained SEA-induced T cell lines from five patients with chronic schistosomiasis japonica, and tested their proliferative response to molecular weight fractions of SEA. Although all T cell lines showed strong responses to crude SEA, there was a heterogeneity in fraction-driven responsiveness. All but one T cell line tested failed to respond to SEA fraction I (mol. wt greater than 18 kD). One patient who was typed as HLA-DQw1/w4, did not show proliferation of CD4+ T cells to fraction I; however, a fraction I-driven helper T cell response was observed when we added HU-11 monoclonal antibody specific for HLA-DQw1/w4. This indicated that the patient had helper T cells to the fraction even though their response was suppressed. Because HLA-DQ had an effect on functional expression of suppressor T cells, it was suggested that there was epitope-specific regulation of the T cell response to SEA, and HLA-DQ-controlled immune suppression might be involved in the regulatory system in human chronic schistosome infection.