Stoichiometry of the T cell antigen receptor (TCR) complex: Each TCR/CD3 complex contains one TCR α, one TCR β, and two CD3∈ chains

Abstract

The stoichiometry of the subunits that comprise the T cell antigen receptor (TCR) complex is not completely known. In particular, it is uncertain whether TCR α and TCR β proteins are present in the TCR complex as one or multiple heterodimeric pairs. In this study we have used mice transgenic for two different TCR α and two different TCR β proteins to determine the number of TCR α and TCR β chains in a single TCR complex. Individual thymocytes and splenic T cells from double TCR transgenic mice simultaneously expressed all four transgenic TCR proteins on their surfaces. Because the individual TCR α and individual TCR β proteins were biochemically distinguishable, we were able to examine associations among the transgenic TCR products. We found that each TCR α chain paired with each TCR β chain, but that each TCR complex contained only one TCR α and one TCR β protein. Furthermore, quantitative immunofluorescence revealed that T cells expressed twice as many CD3∈ as TCR β proteins. These findings demonstrate that there are precisely one TCR α, one TCR β, and two CD3∈ chains in each TCR/CD3 complex expressed on the surfaces of both thymocytes and mature T cells.