CTLA4-Ig blocks allogeneic T-cell proliferation stimulated by FL cells. Cocultures of allogeneic T cells and FL cells were performed as described in the Fig 4 legend. CTLA4-Ig (10 μg/mL) was added to the FL cells 30 minutes before coculture and was present throughout the culture. As control an irrelevant fusion protein (control-Ig, 10 μg/mL) was used. Approriate controls (T cells, FL cells) were less than 1,800 cpm. Three experiments with three different T-cell donors were performed (shown here FL4, FL12, and FL16).