| The alpha beta T Cell Receptor (TCR) is a multi-subunit protein complex composed of an alpha beta heterodimer in complex with CD3 subunits (epsilon, gamma, delta, zeta). The TCR endows T lymphocytes with immune specificity and controls their effector functions. Each person possesses a vast repertoire of TCRs that is generated by the well-studied processes of somatic recombination and thymic selection. pMHC multimers have been generated as a means for studying antigen specific T cell responses. Until now, testing the structural integrity of these reagents was not possible and posed a critical problem for those using the technology. While some groups study antigen specific T cell responses, others are more focused on defining the structure of the TCR/CD3 complex. For some time the stoichiometry of the complex has been debated, but a composition of alpha, beta, epsilon, gamma, epsilon, delta, zeta, zeta is generally agreed upon. The currently accepted model represents a monovalent complex; however, previously published work proposed a model for bivalent TCR complexes (alpha, beta, epsilon, gamma, epsilon, delta, zeta, zeta * 2). To elucidate the valency of the TCR, we have generated a novel antibody against the human TCRalpha chain, as well as new technological platforms including immunoprecipitation detected by flow cytometry (IP-FCM) and size exclusion chromatography. The sensitivity of these techniques allows for an accurate determination between the possibility of a monovalent, bivalent, and multivalent protein complex. Our results strongly suggest that a population of surface expressed, fully assembled TCRs exist as a bivalent complex in its native state. Further investigation is required to determine the functional relevance of the bivalent TCR complex. With a more sound understanding of the biochemical structure of the TCR, more effective manipulation strategies of T cell mediated immune processes can be achieved. |
