C3AR1 and endometriosis: Other members of the complement activation pathway, such as complement C3a receptor 1 (C3AR1) and V-set and immunoglobulin domain containing 4 (VSIG4), are also known in endometriosis, and upregulation of complement and coagulation pathways in endometriosis has been well-reported in several studies (15, 29, 39, 40).