Identification of the ligands of gamma delta T cells

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The purpose of this study is to characterize the T cell receptor (TCR) complex of dendritic epidermal T cells (DETC) as a representative of gamma delta T cells and to identify a possible ligand (s) of TCR gamma delta.TCR is composed of TCR alpha beta or TCR gamma delta associated with CD3 gamma, delta, epsilon and zeta-zeta homodimer. In zeta-chain deficient mice, the degree of TCR expression is significantly reduced. We examined TCR expression of gamma delta T cells which are localized in epithelia and found that the expression of TCR in these mice was not reduced at all. By immunoprecipitation using anti TCR antibodies, gamma chain of Fc receptor for IgE (Fc epsilon R1 gamma=Fc gamma) was utilized instead of zeta chain in DETC and IEL.The signicance of the presense of Fc gamma chain in signal transduction or physiological functions of gamma delta T cells is now under investigation.With regard to the ligands of gamma delta T cells, the most probable cadidates were heat shock proteins (HSP). We tested several HSPs by fluorescence microscopy, FACS and T cell proliferation assay. DETC,neither freshly semi-purified cells nor cell lines did bind or respond to any HSPs tested. We concluded that the ligands of DETC were not HSPs.We next examined the cytokine responsiveness of DETC using DETC cell lines (8.27SD and 10.31). We wanted to know whether cytokines produced by keratinocytes are able to affect the functions of DETC.DETC responded to IL-2 or IL-4 equally well but not IL-7 which was thought to be a growth factor of gamma delta T cells. The epidermal cytokines could not influence the response.In Aly mice, there are no lymphnodes developed. We determined whether DETC were still present or not. In Aly mutant mice, DETC were completely normal in number and the expression of TCR gamma delta. We now investigate whether the functions of DETC are also normal or not.