A new subunit of the human T-cell antigen receptor complex

Abstract

The T-cell antigen receptor binds antigen in association with a cell surface molecule encoded by the major histocompatibility complex (MHC)¹. MHC restricted recognition of antigen by this receptor leads to the complex pattern of programmed gene expression that characterizes T-cell activation. The eventual understanding of human T-cell function will require the complete elucidation of the structure of the human T-cell antigen receptor. On human T cells, clonally determined, disulphide-linked α and β chains of the receptor are non-covalently and stoichiometrically associated with three additional polypeptides known as the T3 complex^2,3. These receptor subunits are glycoproteins of relative molecular mass (M_r) 25,000 (25K) and 20K (γ and δ) and a non-glycosylated 20K protein (ε). Our studies of murine T cells show that the mouse T-cell antigen receptor consists of at least seven distinct polypeptide chains^4–6. In addition to clonotypic α and β chains, the murine complex consists of glycoproteins of 26K and 21K and endoglycosaminidase F (endo F)-insensitive polypeptides of 25K, 21K and 16K. The latter, which we have termed ζ (zeta), exists as a homodimer within the complex. The 26K component (gp26) has been shown to be the murine analogue of the human δ chain^6,7. Other cross species homologies remain to be established, however none of the described human receptor components appear similar to the murine ζ polypeptide. We report here the use of an antiserum raised against the murine ζ subunit to identify a previously unrecognized component of the human T-cell antigen receptor. This human protein is T-cell specific and biochemically similar to the murine ζ polypeptide.