THE GAMMA-CHAIN OF THE HIGH-AFFINITY RECEPTOR FOR IGE IS A MAJOR FUNCTIONAL SUBUNIT OF THE T-CELL ANTIGEN RECEPTOR COMPLEX IN GAMMA-DELTA-T-LYMPHOCYTES

T-cell activation is a consequence of the clonotypic T-cell antigen receptor (TCR) binding to an antigen followed by signal transduction via the invariant subunits of the TCR/CD3 complex. Gammadelta TCR cells are a small subset of T cells that populate both the epithelial and lymphoid tissues and have unique antigen specificity and function. However, the composition of invariant chains within the gammadelta TCR/CD3 complex has not been well characterized. Here we report that, unlike the majority of alphabeta T cells, gammadelta T cells isolated from spleen and intestinal epithelial tissue express high levels of the gamma chain of the high-affinity receptor for IgE (FcepsilonRIgamma) as one invariant subunit of their TCR/CD3 complex. FcepsilonRIgamma exists as both a homodimer and a heterodimer associated with the TCRzeta chain. Moreover, stimulation of the gammadelta TCR results in rapid tyrosine phosphorylation of FcepsilonRIgamma. Our results suggest that utilization of distinct receptor signaling components may enable the coupling of antigen stimulation to the activation of different signal transduction pathways in alphabeta and gammadelta T cells.