C5AR1 and obesity due to melanocortin 4 receptor deficiency: In contrast, increased levels of C3, properdin, C1q, factors H and B, C4, and adipsin and decreased levels of circulating C2 and C5a have been associated with successful implantation as indicated by a study comprising Middle Eastern (Qatar) women with obesity undergoing in vitro fertilization (IVF)-assisted conception (341).