A. Representative flow plots of recipient spleen cells from WT B6 and C3ar1−/− recipients of BALB/c heart grafts isolated on day 6 post-transplant, stimulated with BALB/c (donor) APCs, and stained for intracellular expression of IFNγ (top), TNFγ (middle) or extracellular CD107a/b (bottom), gated on CD8+ T cells. Numbers depict the % of cytokine+ or CD107+ cells within the outlined region. No IFNγ or TNFγ was detected following stimulation with syngeneic B6 APCs (data not shown). B-D. Quantified percentages (left panels) and total numbers (right panels) of donor-reactive IFNγ-producers (B), TNFγ-producers (C) or CD107a/b+ (D) CD8+ T cells are shown. n=8/group. E. Quantified frequencies of IFNγ-producing CD4+ and CD8+ T cells from GIL (see gating strategy in Figure S2) obtained on day 6 post-transplant from WT and C3ar1−/− recipients of BALB/c hearts. n=7/group. *p<0.05, **p<0.01, ***p<0.001; ns, not significant.