C5aR plays an inhibitory role in Matrigel plug angiogenesis. (A) Angiogenesis was assessed using the in vivo Matrigel plug assay. (A) Six hours and 3 days after Matrigel implantation, C57BL/6 WT mice were injected with control IgG or anti-C5 (clone BB5.1, 750 μg per mouse). After 7 days, angiogenesis was assessed within the explanted Matrigels. Data are mean ± SEM (n = 10 Matrigels per group) and are shown as percentage of control. Area of neovascularization in WT mice treated with IgG control represents the 100% value. *P < .005. (B) Matrigel angiogenesis was quantified in WT and C5aR^−/− mice. Data are mean ± SEM (n = 5 Matrigels per group) and are shown as percentage of control. The area of neovascularization of WT mice represents the 100% control. *P < .01. (C) Six hours after Matrigel implantation, WT and C5aR^−/− mice were injected with control liposomes or clodronate liposomes to deplete macrophages and after 7 days angiogenesis was assessed within the explanted Matrigels. Data are mean ± SEM (n = 8 Matrigels per group) and are shown as percentage of control. Area of neovascularization in WT mice treated with control liposomes represents the 100% control. *P < .05; ns, not significant.