Evidence for the T3-associated 90K heterodimer as the T-cell antigen receptor

Abstract

Several surface molecules appear to be involved in antigen recognition by human T lymphocytes including the monomorphic 20/25K T3 structure present on all mature T lymphocytes and the subset-specific associative recognition elements, T4 and T8 (refs 1–8). More recently, Ti₁, a clonally unique antigen recognition structure comprised of a 49,000 molecular weight (49K) α-chain and a 43K β-chain, linked to T3 was identified on a major histocompatibility complex (MHC) class I specific T8⁺ T-cell clone, CT8_III (ref. 9). To determine whether analogous receptor molecules could be found on other T-cell clones of differing specificity, we produced monoclonal antibodies against a clonal structure (Ti₂) on an MHC class II specific T4⁺ lymphocyte, CT4_II, derived from the same donor as CT8_III. The Ti₂ structure on CT4_II is shown here to be a disulphide-linked heterodimer like Ti₁ on CT8_III and is composed of summits of similar molecular weight. Monoclonal antibodies against Ti₂ or Ti₁ block antigen specific functions of the respective clone without showing any cross-reactivity. These findings suggest that each T lymphocyte, regardless of subset derivation or specificity, uses an analogous Ti heterodimer for antigen specific function. The latter is linked to T3 and expressed on the cell surface at an identical density (30,000–40,000 sites per cell).