Partial characterization of T cell components related to defined V H (V T) markers

Abstract

Certain antigen-binding surface molecules and factors of T cells possess serological determinants related to immunoglobulin (Ig)-heavy-chain-variable regions (V H). We obtained sufficient quantities (> 100 μg) of homogenous V H-related T-cell molecules (V TM) 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 V TM from formic acid-solubilized T cells. The V TM from murine thymocytes and T-cell lines had M r of 65,000–68,000. The V TM from distinct cell lines differ by isoelectric focusing and resolution of tryptic peptides indicating clonal restriction. V TM lack conventional light- or heavy-chain-constant region determinants but cross-react with antisera directed against defined V Ha allotypes and J H peptides. The detection of a cross-reaction with a synthetic J H peptide is consistent with recently published data identifying J H-related sequences in putative T-cell receptor genes. The amino acid compositions of the V TM 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 V H-bearing T-cell products are not classical Ig, but bear limited V H-cross-reactive determinants.