Distinct structure and signaling potential of the gamma delta TCR complex

Alpha beta and gamma delta T cells are distinguished by the clonotypic subunits contained within their TCRs. Although the alpha beta TCR has been well characterized, much less is known about the gamma delta TCR. Here, we report that, unlike alpha beta T CRs, most gamma delta TCRs expressed on ex vivo gamma delta T cells lack CD3 delta. Despite this structural difference, signal transduction by the gamma delta TCR is superior to that of the alpha beta TCR, as measured by its ability to induce calcium mobilization, ERK activation, and cellular proliferation. Additionally, the TCR complexes expressed on primary gamma delta T cells contain only zeta zeta homodimers; however, following activation and expansion, Fc epsilon R1 gamma is expressed and is included in the gamma delta TCR complex. These results reveal fundamental differences in the primary structure and signaling potential of the alpha beta- and gamma delta TCR complexes.