Figure 4.

Inhibition of cytokine production of CD28^−/− T cells by B7-1 transfectants is prevented by anti–B7-1 or by anti-CTLA4 mAb. T cell stimulations were performed as in Fig. 3 without additions, or in the presence of anti–B7-1 mAb, anti-CTLA4 mAb, or the combination. IL-2 production was determined at 24 h. Similar results were obtained for IFN-γ production (data not shown), and in at least two separate experiments.