Evidence for involvement of the gamma, delta T cell antigen receptor in cytotoxicity mediated by human alloantigen-specific T cell clones.

The vast majority of mature T cells express the alpha, beta TCR and use this receptor to recognize Ag in association with MHC determinants. Recent reports indicate that a small subpopulation of CD3+ T cells does not express alpha, beta TCR and lacks CD4 and CD8 molecules, but expresses another TCR heterodimer designated gamma, delta. To date, however, there are very few examples of gamma, delta TCR-bearing T cells which have Ag-specific functions and the precise role of the gamma, delta TCR remains unknown. In an attempt to explore the function of the gamma, delta TCR in man, we generated a panel of CD3+, CD4-, CD8- T cell clones from cultures of normal T cells stimulated with allogeneic lymphoblastoid cell line (LCL). All of the clones stained with mAb to gamma, delta TCR determinants, and Northern blot analysis of total cellular RNA revealed mature gamma- and delta-chain transcripts and immature beta-chain transcript. The clones displayed cytolytic activity against their specific stimulating LCL, but not irrelevant LCL, and killing was inhibited by a mAb to HLA class I (HLA-A,B,C) determinants, suggesting that these cells recognized class I MHC antigenic determinants on specific stimulator/target cells. Cytolysis by these clones was markedly inhibited by low concentrations (0.00001 to 0.001 microgram/ml) of mAb to CD3 or TCR delta-chain, but high concentrations (0.1 to 20 micrograms/ml) of the same antibodies enhanced cytotoxicity. When absorbed to plastic tissue culture wells, anti-CD3 mAb stimulated the clones to proliferate. These results indicate that alloantigen specific, gamma, delta TCR+, CD4-, CD8- T cell clones can be reproducibly generated in vitro, and that the gamma, delta TCR plays a direct role in the specific recognition and cytolysis displayed by these clones.