Specificity of OKT4⁺ cytotoxic T lymphocyte clones

OKT4⁺, HLA-DR-specific CTL were cloned by limiting dilution, and two clones were evaluated. One clone, B8, specifically recognized DR6 antigens, whereas another clone, C6, recognized an Ia-like determinant on some DR 3, 5, and 6 target cells. Both clones were OKT3⁺, OKT4⁺ and OKT8^-, and their cytolysis could be blocked by OKT3 and OKT4, but not OKT8, antibodies. A panel of monoclonal antibodies that recognize DR molecules blocked target cell recognition by these OKT4⁺ CTL. Although clone B8 recognized a DR6-specific determinant, clone C6 appeared to recognize a supratypic determinant that may be common to some DR molecules (e.g., MT2) or possibly another human Ia-like antigen (e.g. SB). The availability of OKT4⁺ CTL clones should help to dissect the Ia-like antigens recognized by human T cells.