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 re ceptor (TCR) binding to an antigen followed by signal transduction via the invariant subunits of the TCR/CD3 complex. Gammadelta TCR cells a re a small subset of T cells that populate both the epithelial and lym phoid tissues and have unique antigen specificity and function. Howeve r, the composition of invariant chains within the gammadelta TCR/CD3 c omplex has not been well characterized. Here we report that, unlike th e majority of alphabeta T cells, gammadelta T cells isolated from sple en and intestinal epithelial tissue express high levels of the gamma c hain of the high-affinity receptor for IgE (FcepsilonRIgamma) as one i nvariant 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 utilizat ion of distinct receptor signaling components may enable the coupling of antigen stimulation to the activation of different signal transduct ion pathways in alphabeta and gammadelta T cells.