Effect of H2-Bf^-/-and C4^-/-macrophages on immune stimulation. Primed alloreactive CD4⁺ T cells were prepared from 4 BALB/c mice. Thioglycollate-elicited macrophages were prepared from WT (C57BL/6), C3^-/-, C4^-/-, and H2-Bf^-/- mice (6 mice in each group). Macrophages (2 × 10⁵) from each mouse were cocultured with 2 × 10⁵ T cells. (A-B) T-cell activation was assessed at 3 days after culture by measuring the production of IL-2 and IFN-γ by ELISA. (C) T-cell proliferation was assessed at 96 hours after culture by measuring the incorporation of ³H-thymidine. Data were analyzed by Student t test. P values are for comparisons between complement-deficient and complement-sufficient macrophages; ns, no significant difference. Two further experiments were undertaken, and the results of these confirm the data shown in panel A (see Figure S5).