Given the well-established disadvantageous role for C5aR, and the efficacy of C5aR antagonists and anti-C5a antibodies in acute DSS- and TNBS-induced colitis in rodents [12]–[15], it may be of interest to assess if C3aR and C5aR co-operate in IBD pathogenesis. This evidence concerns the gene C3AR1 and inflammatory bowel disease.