Partial Amino Acid Sequence of Monoclonal Extracellular Antigen-Specific T Cell Proteins

Abstract
Antigen-specific molecules secreted by murine T cell hybrids (TABM) specific for 4-hydroxy 3-nitrophenyl (NP) or azobenzenearsonate (ABA) were purified from ascitic fluid by ion exchange chromatography and/or affinity for antigen. Partial amino acid sequence of reduced Mr 72,000 NP-specific polypeptides and Mr 20,000 peptides prepared by treatment of the ABA-specific immunoprotein with cyanogen bromide was obtained and a septapeptide of the NP-specific TABM shared 3/7 residues with the ABA-specific TABM. Both TABM shared residues present in 95% T cell receptor for antigen (TCR) VaL subgroup I and 83–96% murine immunoglobulin VK Fr3. These results provide evidence that extracellular antigen-specific T cell proteins are soluble analogues of TCR aL chains and belong to the immunoglobulin supergene family.