C5AR1 and rheumatoid arthritis: As one of the key effector functions, C5a-induced C5aR1 activation, is involved in numerous kidney diseases, but also cardiac remodeling in hypertension (46, 47), psoriasis (48), rheumatoid arthritis (49), complications in sepsis (50), neuropathic pain (51), or hidradenitis suppurativa (52).