The Human T Cell Receptor: Analysis with Cytotoxic T Cell Clones

Employing human T lymphocyte clones and monoclonal antibodies to their surface glycoproteins, the antigen receptors on these cells have been defined. Based on functional and biochemical data, it is shown that each T cell displays two major recognition units on its surface. One structure consists of the antigen-binding region (Tin-T3) which views antigen X in the context of a polymorphic region of an MHC molecule. A second (T8 or T4) serves as an associative recognition structure for a constant region of the class I or class II molecule. The antigen-binding structure is a heterodimer of disulfide linked 49KD and 43KD subunits, which contains clonally unique variable regions. These are non-covalently associated with the 20/25KD monomorphic T3 molecule expressed on all mature human T lymphocytes. The associative-recognition element on an individual clone is either T8 or T4, depending on its subset derivation. It is likely that these glycoproteins bind to constant regions of class I or class II molecules, respectively, and are independent of the Tin-T3 complex complex.