Figure 4.

CD94/NKG2A receptor inhibits the specific cytolytic activity of MLC-derived T cell populations or clones. Lymphocytes were cultured in MLCs with irradiated allogeneic cells. IL-15 or IL-2 were added at day 2 and cultures were continued for additional 10 days. Cells cultured in IL-15 were harvested and analyzed for the coexpression of CD94 or NKG2A and CD3 (A and B). (C) Most cells recovered in this experiment were CD8⁺. Parallel cultures supplemented with IL-2 contained only 5% CD94⁺ T cells. NKG2A⁺ cells were <1% (data not shown). Both MLC populations were analyzed for cytolytic activity (D) against ⁵¹Cr-labeled PHA blasts bearing the stimulating alloantigens at different effector/target ratios either in the absence of added mAb (□) or in the presence of anti-CD94 (•) or anti-HLA-class I mAb (▴). Each point represents the mean of duplicate experiments. (E) Three representative allospecific CD8⁺ clones expressing both CD94 and NKG2A (KK11, KK20, and KK26) are shown. Two allospecific CD8⁺ CD94⁺ clones that did not express NKG2A are shown for comparison. Again, the effect of addition of anti-CD94 mAb (solid bars) on the specific lysis of ⁵¹Cr-labeled PHA blasts derived from the donor used as stimulator is evaluated in comparison to controls (i.e., no mAb added, open bars) or to cytolytic assays to which anti-class I mAb has been added (hatched bars). The effector/target ratio was 2:1.