Stoichiometry of the murine γδ T cell receptor

The T cell receptor for antigen (TCR) complex is organized into two functional domains: the antigen-binding clonotypic heterodimer and the signal-transducing invariant CD3 and TCRzeta chains. In most vertebrates, there are two different clonotypic heterodimers (TCRalphabeta and TCRgammadelta) that define the alphabeta and gammadelta T cell lineages, respectively. alphabeta- and gammadeltaTCRs also differ in their invariant chain subunit composition, in that alphabetaTCRs contain CD3gammaepsilon and CD3deltaepsilon dimers, whereas gammadeltaTCRs contain only CD3gammaepsilon dimers. This difference in subunit composition of the alphabeta- and gammadeltaTCRs raises the question of whether the stoichiometries of these receptor complexes are different. As the stoichiometry of the murine gammadeltaTCR has not been previously investigated, we used two quantitative immunofluorescent approaches to determine the valency of TCRgammadelta heterodimers and CD3gammaepsilon dimers in surface murine gammadeltaTCR complexes. Our results support a model of murine gammadeltaTCR stoichiometry in which there are two CD3gammaepsilon dimers for every TCRgammadelta heterodimer.