Analysis of immunoregulatory anti-idiotypic antibodies during human schistosomiasis japonica.

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We analyzed immunological roles of anti-idiotypic T cell responses during human schistosomiasis japonica. Sera of chronic patients induced significant proliferation of T cells from individuals of previous infection. The responding cells were positive for CD3 and CD4, but were CD8-negative. Those T cells produced IFN- in response to the infected sera, whereas no detectable IL-4 and IL-5 were produced. This suggested that Th1 cells were reactive to the sera, and those could be antagonistic to Th2 cells which were tightly involved in granulomatous hypersensitivity to schistosome eggs. The serum factor(s) was observed in IgG fraction, but was different from an anti-schistosome egg antibody. In some cases chronic sera induced responses of established T cell lines specific for Schistosoma japonicum egg antigen, and it was thus highly likely that the serum factor was anti-idiotypic IgG recognizing antibodies to anti-S. japonicum egg antigen.Such anti-idiotypic antibodies were observed only in fresh patients, however, no activity was observed in individuals who had been treated more than 7 years before. When we compared the reactivities of "fresh" and "old" sera to the egg antigen fractionated by HPLC, a 400kD fraction(s) was recognized only by "fresh" patient sera. The difference in specificity of anti-schistosome IgG seemed to have influence on anti-idiotypic antibody responses in various infection phases during human infection of S. japonicum.