Kazatchkine M D, Fearon D T
Unité d'Immunopathologie and INSERM U28, Hôpital Broussais, Paris, France.
Immunodefic Rev. 1990;2(1):17-41.
CR1 (CD35) and CR2 (CD21) are structurally related integral transmembrane glycoproteins that function as cellular receptors for human C3b and C3dg, respectively. The primary sequence of the most common structural allotype of CR1 and that of CR2 have been established, and ligand binding on the molecules has been mapped. CR1 and CR2 genes are located in close vicinity in the RCA locus of chromosome 1. CR1 has a wide cellular/tissular distribution and mediates a variety of biologic functions, including the transport of C3-bearing immune complexes on erythrocytes, enhancement of phagocytosis, induction of IL-1 secretion and enhancement of B-cell differentiation. Expression of CR2 is restricted to B lymphocytes and follicular dendritic cells. The receptor modulates B-cell growth. CR2 also serves as the receptor for EBV and determines the cellular tropism of the virus. This review discusses the molecular biology and functional characteristics of CR1 and CR2. It focuses on alterations of expression of the receptors in disease, with particular emphasis on the genetic and acquired factors that contribute to the defective expression of CR1 in patients with systemic lupus erythematosus.
补体受体1（CR1，即CD35）和补体受体2（CR2，即CD21）是结构相关的整合跨膜糖蛋白，分别作为人C3b和C3dg的细胞受体发挥作用。CR1最常见结构同种异型和CR2的一级序列已确定，并且分子上的配体结合位点也已定位。CR1和CR2基因位于1号染色体RCA基因座附近。CR1具有广泛的细胞/组织分布，并介导多种生物学功能，包括红细胞上携带C3的免疫复合物的转运、吞噬作用增强、白细胞介素-1分泌诱导以及B细胞分化增强。CR2的表达仅限于B淋巴细胞和滤泡树突状细胞。该受体调节B细胞生长。CR2还是EB病毒的受体，并决定病毒的细胞嗜性。本文综述讨论了CR1和CR2的分子生物学及功能特性。重点关注疾病中受体表达的改变，特别强调导致系统性红斑狼疮患者CR1表达缺陷的遗传和后天因素。
