TCR-ALPHA-BETA CHAINS ASSOCIATE WITH THE PLASMA-MEMBRANE INDEPENDENTLY OF CD3 AND TCR-ZETA CHAINS IN MURINE PRIMARY T-CELLS

The TCR is a multisubunit complex composed of the clonotypic alpha/bet a disulfide-linked heterodimer and noncovalently linked invariant CD3 gamma epsilon and CD3 delta epsilon and TCR zeta chains. Recent studie s demonstrate that the surface expression of CD3 components can occur independently of the clonotypic TCR complexes in both thymocytes and s plenic T cells. In this study, we report that free noncovalently assoc iated TCR alpha beta heterodimers that exist independently of CD3 and TCR zeta chains are expressed on the cell surface of immature thymocyt es and peripheral T cells, but not of T cell lines and T cell hybridom as. This suggests that the regulation of surface expression of TCR alp ha beta heterodimers differs between primary T cells and T cell lines or T cell hybridomas. The isolation and biochemical characterization o f surface clonotype-independent CD3 complexes and free membrane-associ ated TCR alpha beta complexes may provide a structural basis for the q uantitative difference in amount of T cell proliferation stimulated by anti-CD3 epsilon and anti-TCR beta.