| First Author | Prabagar MG | Year | 2013 |
| Journal | Cell Death Differ | Volume | 20 |
| Issue | 4 | Pages | 535-45 |
| PubMed ID | 23238564 | Mgi Jnum | J:228267 |
| Mgi Id | MGI:5705729 | Doi | 10.1038/cdd.2012.160 |
| Citation | Prabagar MG, et al. (2013) SIGN-R1, a C-type lectin, enhances apoptotic cell clearance through the complement deposition pathway by interacting with C1q in the spleen. Cell Death Differ 20(4):535-45 |
| abstractText | Complements, such as C1q and C3, and macrophages in the splenic marginal zone (MZMs) play pivotal roles in the efficient uptake and processing of circulating apoptotic cells. SIGN-R1, a C-type lectin that is highly expressed in a subpopulation of MZMs, regulates the complement fixation pathway by interacting with C1q, to fight blood-borne Streptococcus pneumoniae. Therefore, we examined whether the SIGN-R1-mediated classical complement pathway plays a role in apoptotic cell clearance and immune tolerance. SIGN-R1 first-bound apoptotic cells and this binding was significantly enhanced in the presence of C1q. SIGN-R1-C1q complex then immediately mediated C3 deposition on circulating apoptotic cells in the MZ, leading to the efficient clearance of them. SIGN-R1-mediated C3 deposition was completely abolished in the spleen of SIGN-R1 knockout (KO) mice. Given that SIGN-R1 is not expressed in the liver, we were struck by the finding that C3-deposited apoptotic cells were still found in the liver of wild-type mice, and dramatically reduced in the SIGN-R1 KO liver. In particular, SIGN-R1 deficiency caused delayed clearance of apoptotic cells and aberrant secretion of cytokines, such as TNF-alpha, IL-6, and TGF-beta in the spleen as well as in the liver. In addition, anti-double- and single-stranded DNA antibody level was significantly increased in SIGN-R1-depleted mice compared with control mice. These findings suggest a novel mechanism of apoptotic cell clearance which is initiated by SIGN-R1 in the MZ and identify an integrated role of SIGN-R1 in the systemic clearance of apoptotic cells, linking the recognition of apoptotic cells, the opsonization of complements, and the induction of immune tolerance. |
