Human lymphocytes expressing a TCR gamma/delta.

A minor subset of T lymphocytes express a TCR composed of gamma and delta chains. This subset differs from conventional T cells for a number of phenotypic and functional characteristics. TCR gamma/delta + cells simultaneously lack both CD4 and CD8 antigens. Cloning of CD4-8-peripheral blood lymphocytes, under limiting dilution conditions, revealed that they are homogeneously composed of cytolytic cells which efficiently lyse tumor target cells. Formal proofs have been provided that TCR gamma/delta + cells are able to recognize antigens. For example, they proliferated in response to allogeneic mixed lymphocyte culture (MLC), in addition MLC-derived TCR gamma/delta + cells specifically lysed PHA-induced blast cells bearing the stimulating alloantigens. The selection of monoclonal antibodies (MoAbs) specific for TCR gamma/delta molecules allowed to identify two distinct subsets of TCR gamma/delta + cells. These MoAbs, termed BB3 and delta-TCS-1 (or the equivalent A13) respectively, induced specific activation of cloned cells expressing the corresponding antigenic determinants (as assessed by measurements of intracellular Ca2+ and/or lymphokine production of cytolytic activity). Analysis of the distribution of subsets expressing different forms of TCR gamma/delta, showed that the BB3-reactive form is prevalent in the peripheral blood. In contrast, delta-TCS-1-reactive cells are relatively infrequent in peripheral blood, but represent the majority of TCR gamma/delta + in the tissues.