Richards M L, Katz D H
Division of Immunology, Medical Biology Institute, La Jolla, CA 92037.
Crit Rev Immunol. 1991;11(2):65-86.
Recent studies have established that the low affinity Fc receptor for IgE (Fc epsilon RII/CD23) is a structurally and functionally unique immunoglobulin receptor. DNA sequence analysis predicts that, in contrast to other FcR, Fc epsilon RII is not a member of the immunoglobulin gene superfamily and, indeed, is inserted into the membrane in opposite orientation from most other membrane proteins. While the Fc epsilon RII of macrophages, eosinophils, and platelets mediate IgE-dependent cytotoxicity and promote phagocytosis of IgE-antigen complexes, the function of Fc epsilon RII on B lymphocytes remains unclear. Much effort has been directed toward establishment of its role in IgE regulation, but the plurality of B cell Fc epsilon RII expression, i.e. greater than 90% of the mu + /delta + B lymphocytes, is incongruous with simply a role in regulating only IgE responses. Hence, the discovery that Fc epsilon RII is identical to the B-cell activation antigen, CD23, together with its novel structural features, suggests an additional more important role for this interesting protein and would explain the disparity between a commonly expressed receptor with apparently limited functions.
最近的研究证实，免疫球蛋白E的低亲和力Fc受体（FcεRII/CD23）是一种结构和功能独特的免疫球蛋白受体。DNA序列分析预测，与其他FcR不同，FcεRII不是免疫球蛋白基因超家族的成员，实际上，它以与大多数其他膜蛋白相反的方向插入膜中。虽然巨噬细胞、嗜酸性粒细胞和血小板的FcεRII介导IgE依赖性细胞毒性并促进IgE-抗原复合物的吞噬作用，但FcεRII在B淋巴细胞上的功能仍不清楚。人们为确定其在IgE调节中的作用付出了很多努力，但B细胞FcεRII表达的多样性，即超过90%的μ+/δ+B淋巴细胞，与仅在调节IgE反应中起作用并不相符。因此，FcεRII与B细胞活化抗原CD23相同这一发现，连同其新颖的结构特征，表明这种有趣的蛋白质还有一个更重要的作用，并可以解释一种普遍表达但功能明显有限的受体之间的差异。
