Myones B L, Dalzell J G, Hogg N, Ross G D
Department of Medicine, University of North Carolina, Chapel Hill 27599.
J Clin Invest. 1988 Aug;82(2):640-51. doi: 10.1172/JCI113643.
Previous investigations of p150,95 (CD11c), the third member of the CD18 membrane glycoprotein family that includes CR3 (Mac-1 or CD11b) and LFA-1 (CD11a), had demonstrated that solubilized p150,95 bound to iC3b-agarose in a manner similar to isolated CR3. The current study showed that membrane surface p150,95 also expressed iC3b-receptor activity and was probably the same as the neutrophil receptor for iC3b- or C3dg-coated erythrocytes (EC3bi or EC3dg) that had been previously designated CR4. Normal neutrophil and macrophage CR4-dependent EC3bi rosettes were inhibited by monoclonal anti-p150,95, and cells from a patient with CD18 deficiency did not form CR4-dependent EC3bi rosettes. With neutrophils that bore large amounts of CR1 and CR3 and little p150,95, EC3bi were found primarily via CR1 and CR3, and demonstration of p150,95-dependent rosettes required large amounts of fixed iC3b, low-ionic strength buffer, and antibody blockade of CR1 and CR3. By contrast, culture-derived macrophages expressed eight times more p150,95 than did monocytes and EC3bi were bound to both p150,95 and CR3 when EC3bi bore small amounts of fixed iC3b and assays were carried out in isotonic buffer. Comparison of the amounts of CR1, CR3, and CR4 in various tissues by immunoperoxidase staining revealed that CR4 was the most abundant C3 receptor molecule on tissue macrophages, and suggested that CR4 might be involved in clearance of C3-opsonized particles or immune complexes.
先前对p150,95（CD11c）的研究表明，其作为CD18膜糖蛋白家族的第三个成员，包括CR3（巨噬细胞-1或CD11b）和LFA-1（CD11a），溶解的p150,95以类似于分离的CR3的方式与iC3b-琼脂糖结合。当前研究表明，膜表面的p150,95也表达iC3b受体活性，并且可能与先前命名为CR4的iC3b或C3dg包被的红细胞（EC3bi或EC3dg）的中性粒细胞受体相同。正常中性粒细胞和巨噬细胞的CR4依赖性EC3bi花环被单克隆抗p150,95抑制，并且来自CD18缺陷患者的细胞不形成CR4依赖性EC3bi花环。对于携带大量CR1和CR3且p150,95很少的中性粒细胞，主要通过CR1和CR3发现EC3bi，并且p150,95依赖性花环的证明需要大量固定的iC3b、低离子强度缓冲液以及CR1和CR3的抗体阻断。相比之下，培养来源的巨噬细胞表达的p150,95比单核细胞多八倍，并且当EC3bi携带少量固定的iC3b且在等渗缓冲液中进行检测时，EC3bi与p150,95和CR3都结合。通过免疫过氧化物酶染色比较各种组织中CR1、CR3和CR4的量，发现CR4是组织巨噬细胞上最丰富的C3受体分子，并表明CR4可能参与C3调理颗粒或免疫复合物的清除。
