C3AR1 and periodontitis: Compared to C3ar1+/+ and C3ar1+/− mice, C3ar1−/− mice retained gingival papilla morphology, relative epithelial integrity and significantly reduced neutrophil infiltration in the ligated side, with no significant differences between C3ar1+/+ and C3ar1+/− mice, indicating that C3aR deletion alleviates periodontal soft tissue destruction and inflammatory cell infiltration (Green arrow) in periodontitis mice (Fig. 3a, b).