Partial characterization of T cell components related to defined VH (VT) markers

Certain antigen-binding surface molecules and factors of T cells possess serological determinants related to immunoglobulin (Ig)-heavy-chain-variable regions (VH). We obtained sufficient quantities (greater than 100 micrograms) of homogenous VH-related T-cell molecules (VTM) for biochemical studies from normal murine thymocytes and by growing large quantities of monoclonal T-cell leukemia lines expressing the determinants. A solid phase immune adsorbent prepared from the IgG fraction of rabbit anti-IgT serum was used to isolate VTM from formic acid-solubilized T cells. The VTM from murine thymocytes and T-cell lines had Mr of 65,000-68,000. The VTM from distinct cell lines differ by isoelectric focusing and resolution of tryptic peptides indicating clonal restriction. VTM lack conventional light- or heavy-chain-constant region determinants but cross-react with antisera directed against defined VHa allotypes and JH peptides. The detection of a cross-reaction with a synthetic JH peptide is consistent with recently published data identifying JH-related sequences in putative T-cell receptor genes. The amino acid compositions of the VTM were distinct from those of mammalian Ig, major histocompatibility complex (MHC) antigens, and viral glycoproteins, but significant similarities occur with Ig V regions or heavy chains of primitive vertebrates. The results indicate that the VH-bearing T-cell products are not classical Ig, but bear limited VH-cross-reactive determinants.