Segmental homology between T-cell receptors and immunoglobulin variable regions: evidence that antisera to synthetic JH1 peptide react with murine and human T-cell products.

To determine precisely the nature of serological determinants shared between T-cell surface molecules and immunoglobulin variable regions, the capacity of antisera directed against a synthetic peptide corresponding to the entire JH 1 region of classical immunoglobulin plus five residues of the D region were tested for their capacity to bind to T-cell membranes and isolated T-cell products. The anti-JH 1 antisera reacted with normal and monoclonal in vitro grown T-cell lines as judged by microhemagglutination and binding in enzyme-linked immunosorbent assays. Immunologically cross-reactive membrane components disclosed by immunoblot transfer analysis ("Western blots") consisted of major components in the molecular weight range 30-35,000 and minor components in the range 65-70,000. The major product of the human T-cell leukemia line MOLT-3 had an approximate mass of 34,000 Da, a value consistent with the predicted size of the molecule specified by the recently described putative T-cell receptor gene YT35. The 65 to 70,000-Da components are most probably tightly associated dimers of the 30 to 35,000-Da forms. It was possible to align the JH sequences of molecules reactive with the anti-JH 1 antisera and other characterized VH sequences of molecules known to be cross-reactive with T-cell products. This facilitated a comparison disclosing clear segmental homology between the protein sequence derived from the YT35 gene and immunoglobulin VH framework regions sharing approximately 50% of sequence identity. The identification of VH-related T-cell products (termed VT-bearing molecules) with products of putative T-cell receptor genes gained further support by N-terminal sequence of the 68,000-Da product of the 70-N2 T-cell line which showed homology to the predicted N-terminal region of the YT35 product. These serological and protein chemical data, coupled with the comparison to gene sequence, show that T-cell components that bear serological determinants cross-reactive with VH show segmental homology with products of putative T-cell receptor genes and immunoglobulin VH.