Characterization of human lymphocyte subpopulations: alloreactive cytotoxic T-lymphocyte precursor and effector cells are phenotypically distinct from Leu 2+ suppressor cells.

The OKT8/Leu 2+ human T-cell subset contains cells which perform suppressor and cytotoxic functions. We have recently produced two monoclonal antibodies (termed 2D2 and D12) which define four subpopulations of human E+ cells. Previous studies have shown that the Leu 2+ cells that suppress T-cell proliferative responses have the 2D2+D12+ phenotype. In the present studies, we have used these antibodies and fluorescence-activated cell sorter techniques to characterize the phenotype of cytotoxic T lymphocytes generated in allogeneic mixed lymphocyte cultures. These studies indicate that the cytolytic effector cells which recognize class I major histocompatibility antigens express the 2D2+D12- phenotype. The phenotype of the precursor cells for these cytotoxic T cells was similarly demonstrated to be 2D2+D12-. The subset of E+ cells with NK cytolytic activity expressed the 2D2-D12+ phenotype. These data demonstrate that the Leu 2+ precursor and effector cytotoxic T cells reactive against class I alloantigens are phenotypically distinct from the Leu 2+ cells previously shown to suppress T-cell proliferative responses.