Expression of cross-reactive, shared idiotypes on anti-SEA antibodies from humans and mice with schistosomiasis

Immunoaffinity-purified antibodies against Schistosoma mansoni soluble egg Ag (SEA) from infected patients' sera differ idiotypically according to the donor's clinical form of the disease. The Id differ both by their ability to stimulate proliferation of anti-Id T cells and their recognition by anti-Id-specific sera. Also, mice infected with S. mansoni develop anti-Id T and B cell responses against mouse anti-SEA antibodies. We now show that anti-SEA antibodies from serum pools of chronic, but asymptomatic patients (AM1 and AM5) stimulate proliferation of spleen cells from mice infected with S. mansoni. However, AM8, anti-SEA antibodies from hepatosplenic patients, did not stimulate these spleen cells. The murine responses directly parallel patient studies where AM1 and AM5 Id-stimulated human PBMC, but AM8 Id did not. In competitive ELISA, using AM1 or AM-5-specific rabbit antisera or human anti-SEA mAb E5-specific rabbit antiserum, sera from mice infected for 8 and 16 wk (but not from uninfected mice) compete with AM1, AM5, or E5. These sera do not compete in the AM8/anti-AM8 competitive ELISA. Sera from 8-wk-infected mice inhibit more against AM1, AM5, and E5 than do sera from later infections, and anti-SEA immunoaffinity-purified antibodies from 8-wk-infected mice stimulate spleen cells from infected mice more than anti-SEA antibodies from sera of mice late in infection. However, spleen cells from more chronically infected mice are more responsive to either the murine or human anti-SEA antibody preparations than cells from mice with earlier infections. Both the ELISA data and lymphocyte responses indicate that anti-SEA antibodies from mice infected with S. mansoni for 8 wk bear Id cross-reactive with those expressed on anti-SEA antibodies from humans with chronic, asymptomatic schistosomiasis, but not those from hepatosplenic patients.