Figure 1: The systemic clearance of apoptotic cells which is mediated by SIGN-R1 and complement factors. SIGN-R1 first binds to apoptotic cells and this binding is enhanced by interacting with C1q in the splenic marginal zone. The SIGN-R1–C1q complex immediately mediates C3 deposition on apoptotic cells, thus promoting their systemic clearance predominantly in spleen and liver and maintaining immune tolerance. These findings are valuable to identify an integral role of SIGN-R1 and complements in apoptotic cell clearance, linking the recognition of apoptotic cells, their opsonization of complements, and the induction of immune tolerance.