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 TCRζ chains. In most vertebrates, there are two different clonotypic heterodimers (TCRαβ and TCRγδ) that define the αβ and γδ T cell lineages, respectively. αβ- and γδTCRs also differ in their invariant chain subunit composition, in that αβTCRs contain CD3γɛ and CD3δɛ dimers, whereas γδTCRs contain only CD3γɛ dimers. This difference in subunit composition of the αβ- and γδTCRs raises the question of whether the stoichiometries of these receptor complexes are different. As the stoichiometry of the murine γδTCR has not been previously investigated, we used two quantitative immunofluorescent approaches to determine the valency of TCRγδ heterodimers and CD3γɛ dimers in surface murine γδTCR complexes. Our results support a model of murine γδTCR stoichiometry in which there are two CD3γɛ dimers for every TCRγδ heterodimer.