The concept of an immunological network includes the possibility of interactions between receptors on T and B lymphocytes, and such interactions, should they occur, might be expected to influence the repertoire of receptors in each set of cells. Indeed, B cell idiotype specific helper T cells, both MHC-restricted and MHC-unrestricted, have been reported and have been shown to influence the expression of the B cell repertoire. Likewise, it has been reported that B cells may influence the specificity of both regulatory and MHC-restricted T cells. However, interactions between receptors on cloned, MHC-restricted helper T cells and B cells have been difficult to document. Recently, we have taken advantage of an unusual cloned helper T cell line to demonstrate that anti-T cell receptor antibody is produced by direct receptor:receptor interactions between T and B lymphocytes, and that these interactions are not MHC restricted. However, these earlier studies did not address the question of whether such interactions led to activation of B cells expressing multiple distinct antibodies, or whether direct T cell receptor:B cell receptor interactions would lead to an idiotypically restricted B cell response. To address this question, we have now examined both monoclonal and polyclonal responses to the receptor of a conventional, MHC-restricted cloned T cell line, and have shown that these responses are of limited idiotype heterogeneity. Indeed, about 60% of antibodies produced to the receptor of this cloned line share idiotypic determinants, and appear to recognize a single epitope on the receptor. Idiotypically unrelated anti-receptor antibodies, although still specific for the cloned line, recognize what appears to be a distinct epitope on the receptor. These data suggest several conclusions. First, they demonstrate further that direct receptor:receptor interactions between helper T cells and B cells can occur, and can be mutually stimulatory for the two cell types. Second, as shown previously, such interactions are not MHC restricted. Third, such interactions can lead to an idiotypically restricted B cell response. Finally, it is interesting to compared these results with those of other investigators studying idiotype-specific helper T cells. As the cloned line used in this study is a conventional, MHC-restricted, antigen specific helper T cell bearing an alpha:beta heterodimeric receptor complex, and as its interaction with B cells is MHC unrestricted and leads to idiotypically restricted antibody responses, one might propose that such cells are candidates for a clone of an idiotype-specific helper.(ABSTRACT TRUNCATED AT 400 WORDS)