Reduced capacity of C3^-/-macrophages for immune stimulation in vivo. BALB/c mice (n = 12/group) were given either C3^+/+ or C3^-/- C57BL/6 thioglycollate-elicited macrophages by intraperitoneal injection. The primed mice then received a C57BL/6 donor skin graft. T-cell responses in those BALB/c mice were then measured ex vivo by MLR at day 3 of coculture. The production of IL-2 (A) and IFN-γ (B) was measured by ELISA. Skin graft survival is shown in panel C. Data were analyzed by log-rank test. Solid line indicates C3^+/+ macrophages (n = 9); dashed line, C3^-/- macrophages (n = 6). P < .001. An additional experiment is shown in panel D, in which BALB/c mice (n = 10/group) were primed by skin grafting from C57BL/6 donors and rechallenged with C3^+/+ or C3^-/- C57BL/6 macrophages. T-cell responses in those BALB/c mice were then measured ex vivo by MLR. The production of IFN-γ was measured by ELISA (D). (A-B,D) Results from each animal are shown as separate data points, and all data points were analyzed by Student t test. P values are for comparisons between the 2 mouse groups. Additional results for MLR at days 1 to 5 of coculture are presented in Figure S3.