Local complement activation regulates Fas-mediated T-cell apoptosis. (A) Polyclonal naive (> 90% CD62L^hi, CD44^lo, not shown) CD4⁺ H-2^b WT or B6.MRL^lpr T cells were stimulated in vitro with allogeneic H-2^d WT, Daf1^−/−, or C3^−/− macrophages and stained for annexin V on day 4. Results are means plus or minus SD of triplicate wells. The experiment was repeated with identical results. *P < .05. Data are representative of 3 individual experiments. (B) Representative flow plots of annexin V⁺ Mar T cells after stimulation for 3 days with WT, Daf1^−/−, or C3^−/− macrophages and HYDby peptide plus 10 μg/mL anti-FasL antibody or control. The percentage of cells within the gated region is listed in each panel. *P < .05 versus controls. (C) Total live (annexin V⁻) Mar T cells after 3 days in culture with WT or C3^−/− macrophages and HYDby peptide plus 10 μg/mL anti-FasL antibody or control. Results are means plus or minus SD of 2 experiments. *P < .05 versus control antibody. (D) Percentage annexin V⁺ polyclonal H-2^b WT or C5aR^−/− CD4 T cells after 4 days stimulation with allogeneic WT or Daf1^−/− H-2^d macrophages in the presence or absence of 10 μg/mL of anti-FasL antibody. Data are representative of 2 individual experiments. *P < .05 versus WT controls.