Distinct molecular forms of human T cell receptor gamma/delta detected on viable T cells by a monoclonal antibody.

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Abstract
A second type of TCR molecule has been identified on human and murine T lymphocytes, which involves the protein products of the .gamma. and .delta. genes. T lymphocytes, which involves the protein products of the .gamma. and .delta. genes. T lymphocytes bearing this receptor may constitute a separate cell lineage with a distinct immune function. We have produced an mAb, which specifically detects human TCR-.gamma./.delta. in native as well as denatured states, this in contrast to previously used anti-.gamma. chain peptide sera, which only reacted with denatured protein. The receptor occurs in different molecular forms, with or without interchain disulphide bonds, in which a .delta. chain may or may not be detected by cell surface iodination. This mAb is reactive with all these receptor forms. Therefore, this antibody could be used to determine the expression of TCR-.gamma./.delta. on viable human T lymphocytes. In normal individuals, TCR-.gamma./.delta. was found on a subset composing 2-7% of CD3+ lymphocytes in peripheral blood and 0.1-1.0% in thymus. The majority of these cells do not express the CD4 or CD8 antigens, although a significant percent of CD8+ cells was found. TCR-.gamma./.delta.+ cells in peripheral blood are resting lymphocytes, as judged by ultrastructural analysis. T cell clones with different receptor types can display MHC-nonrestricted cytolytic activity, which is shown to be induced by the culture conditions, most likely by growth factors such as IL-2. This strongly suggests that TCR-.gamma./.delta. does not play a role in target cell recognition in MHC-nonrestricted cytotoxicity. The anti-TCR-.gamma./.delta. antibody can specifically induce cytotoxic activity in clones expressing the receptor, but in addition inhibit growth factor induced cytotoxicity, which indicates a regulatory role of the TCR-.gamma./.delta. CD3 complex in MHC-nonrestricted cytotoxicity.