Tas S W, Klickstein L B, Barbashov S F, Nicholson-Weller A
Department of Medicine, Harvard Medical School, Charles A. Dana Research Institute, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
J Immunol. 1999 Nov 1;163(9):5056-63.
Previously, we showed that soluble C1q bound specifically to CR1 on transfected cells. If the CR1-C1q interaction were to participate in immune complex clearance, then this interaction should support E adhesion. Using a tip plate adhesion assay, we found that immobilized C1q mediated adhesion of human E. E binding to C1q was specifically inhibited by polyclonal anti-CR1 Fab fragments. Intact C1 was not efficient as an adherence ligand until it was treated with EDTA or the C1 inhibitor to remove the C1r2C1s2 complex from C1, leaving C1q. Titration of C1q alone, C4b alone, and C1q + C4b indicated that the two complement ligands were additive in their ability to support CR1-mediated adhesion of E. Analysis of binding to immobilized CR1 using a BIAcore instrument documented that C1q, C4b, and C3b binding were independent events. Additionally, C1q-dependent binding of immune complexes and heat-aggregated IgG to E was documented. These experiments confirm that the immune adherence receptor in humans, CR1, is the single receptor for all of the opsonic ligands of complement, provide evidence for a single C1q binding site on LHR-D of CR1, and suggest that C1q may participate in immune clearance.
此前，我们发现可溶性C1q可特异性结合转染细胞上的CR1。如果CR1 - C1q相互作用参与免疫复合物清除，那么这种相互作用应支持红细胞（E）黏附。通过尖端板黏附试验，我们发现固定化的C1q介导人红细胞的黏附。红细胞与C1q的结合可被多克隆抗CR1 Fab片段特异性抑制。完整的C1作为黏附配体效率不高，直到用EDTA或C1抑制剂处理以从C1上去除C1r2C1s2复合物，留下C1q。单独滴定C1q、单独滴定C4b以及滴定C1q + C4b表明，这两种补体配体在支持CR1介导的红细胞黏附能力上具有加和性。使用BIAcore仪器分析与固定化CR1的结合表明，C1q、C4b和C3b的结合是独立事件。此外，还记录了免疫复合物和热聚集IgG与红细胞的C1q依赖性结合。这些实验证实，人类的免疫黏附受体CR1是补体所有调理素配体的单一受体，为CR1的LHR - D上存在单一C1q结合位点提供了证据，并表明C1q可能参与免疫清除。
