Antibodies to synthetic peptides corresponding to variable-region first-framework segments of T cell receptor. Detection of T cell products and cross-reactions with classical immunoglobulins.

Recent studies at the gene level have shown that T cells express rearranged genes for four types of T cell receptors that are strongly homologous to classical immunoglobulins in the joining region and in the framework 1 (Fr1) and 3 segments of the variable region. Based upon the homologies in gene sequence, it follows that the gene products would show similarities in amino acid sequence and in the folding of the proteins so that cross-reactivities in antigenic determinants would be expected between variable regions of the T cell receptors and classical immunoglobulins. We have synthesized peptides corresponding to predicted protein sequences of the Fr1 residues of T cell receptor alpha, beta- and gamma-chains and have produced antibodies in rabbits against these synthetic peptides. Use of antisera and affinity-purified antipeptide antibodies indicated that high-titer antibodies could be raised that were specific for individual Fr1 peptides. Cross-reactions among Fr1 peptides of T cell receptors and immunoglobulin light chains were observed. In addition, some rabbit antisera raised against classical polyclonal immunoglobulins or affinity-purified immunoglobulin-like T cell receptors were found to exhibit binding activity against Fr1 peptides of T cell receptor beta- and gamma-chains. The sequence homology, although real among the Fr1 of T cell receptors and immunoglobulin light chains, is moderate and the antigenic cross-reaction must reflect the configuration and types of amino acids present. The development of antipeptide antibodies holds promise for the characterization of T cell receptors of various T cell sources and also offers a new means for the identification of molecules related to rearranging immunoglobulins.