Immune responses during human schistosomiasis mansoni. XV. Anti-idiotypic T cells can recognize and respond to anti-SEA idiotypes directly.

We previously have shown that former patients and patients with active cases of schistosomiasis mansoni have T lymphocytes in their PBMC that proliferate when exposed to immunoaffinity-purified antibodies against Schistosoma mansoni soluble egg antigens (SEA). These T cell anti-idiotypic responses required the participation of adherent cells, but the role of these cells in the response to the Id has been unclear. We now show that chloroquine does not interfere with Id-elicited stimulation of cells from former patients but completely inhibits their response to the SEA. F(ab')2 fragments of anti-SEA Id are stimulatory, and excess normal human IgG does not alter anti-Id responses. Soluble Id F(ab) fragments are not stimulatory, but rather inhibit stimulation by the intact Id from which they were made. Either intact Id or their F(ab')2 fragments can stimulate non-adherent T cells in the absence of adherent cells if an exogenous source of purified or recombinant human IL-1 is supplied. Nonstimulatory F(ab) fragments can stimulate nonadherent cells if they are bound first to Sepharose 4B and presented in conjunction with IL-1. Thus, T cells from former schistosomiasis patients can react with polyclonal anti-SEA-related Id directly. Under these conditions T cell proliferation requires receptor cross-linking and a source of IL-1 but does not require either "processing" of Id or MHC co-presentation.