EXTRACELLULAR (SOLUBLE) ANTIGEN-SPECIFIC T-CELL PROTEINS RELATED TO THE T-CELL RECEPTOR FOR ANTIGEN (STCRR) - SEROLOGIC AND PRIMARY AMINO-ACID-SEQUENCE SIMILARITY TO T-CELL RECEPTOR-ALPHA CHAINS AND ASSOCIATION WITH CYTOKINES

Antigen-specific-effected immunoregulation by T lymphocytes is mediate d by extracellular proteins produced by T lymphocytes, These immunopro teins bind specifically to nonprocessed antigen and either induce anti gen-specific immunoregulatory T cells (tsfi) or effect regulation (tsf e). T cell proteins that bind specifically to nonprocessed antigen hav e ben termed ''T cell antigen-binding molecules'' (TABM), and by defin ition, tsfe and tsfi are, in part, TABM. To characterize tsfi, tsfe, a nd TABM and understand the relationships and function of these immunop roteins, me have combined the efforts of two laboratories to compare t sfi, tsfe, and TABM isolated by each laboratory, Data obtained in one laboratory were reproduced by the other, and all reagents prepared by each laboratory were exchanged, TABM, tsfi, and tsfe were found to exp ress TCRC alpha epitopes but not TCRC beta epitopes, The amino acid se quence of a tryptic peptide of a T cell hybridoma TABM specific for ni trophenylhydroxy acetate (NP) is similar to a TCR alpha chain and TCR pre-alpha chain amino acid sequence, ELISA and immunoblotting demonstr ated that M-r 77,000 T cell hybrid-derived tsfi, tsfe, and TABM are no ncovalently associated with M-r 15,000-16,000 interleukin-10 (IL-10). ELISA also demonstrated that tsfi and tsfe are associated with I-J. Th e ability of tsfi and tsfe to suppress a mixed lymphocyte reaction was prevented by anti-IL-10 or anti-I-J antibodies, suggesting that antig en-specific immunoregulatory T cell proteins function by an antigen-sp ecific focusing of immunoregulatory cytokines.