Rokeach L A, Jannatipour M, Hoch S O
Agouron Institute, La Jolla, CA 92037.
J Immunol. 1990 Feb 1;144(3):1015-22.
The U snRNP associated B'/B polypeptides are primary targets of Sm autoantibodies in patients with systemic lupus erythematosus. We have bacterially expressed a Sm-B'/B autoantigen from Raji cells as a fusion with the anthranilate synthase protein from Escherichia coli. The recombinant Sm-B'/B fusion displays comparable immunologic reactivity to the native protein when tested with both monoclonal and polyclonal antibodies. To map Sm-B'/B epitopes, we constructed a series of 12 anthranilate synthase fusions spanning different regions of Sm-B'/B and tested such fusions on immunoblots against a panel of characterized sera. In this manner, we have identified six epitopes, five of which overlap the proline-rich carboxyl-terminus of the protein. Some of these epitopes appear to be conformational. The human sera tested can be divided, according to the epitopes they recognize, into six groups. Finally, we have shown that anti-Sm recognition of the (U1)RNP-specific A protein is attributable to cross-reactivity between the Sm-B'/B and A autoantigens.
U1 小核糖核蛋白相关的 B'/B 多肽是系统性红斑狼疮患者中 Sm 自身抗体的主要靶标。我们已通过细菌表达了来自 Raji 细胞的 Sm-B'/B 自身抗原，使其与大肠杆菌的邻氨基苯甲酸合酶蛋白融合。当用单克隆抗体和多克隆抗体进行检测时，重组的 Sm-B'/B 融合蛋白与天然蛋白表现出相当的免疫反应性。为了绘制 Sm-B'/B 表位图谱，我们构建了一系列 12 个邻氨基苯甲酸合酶融合蛋白，它们跨越 Sm-B'/B 的不同区域，并在免疫印迹上针对一组特征明确的血清检测这些融合蛋白。通过这种方式，我们鉴定出了六个表位，其中五个与该蛋白富含脯氨酸的羧基末端重叠。其中一些表位似乎是构象性的。根据所识别的表位，所检测的人血清可分为六组。最后，我们已证明对（U1）核糖核蛋白特异性 A 蛋白的抗 Sm 识别归因于 Sm-B'/B 与 A 自身抗原之间的交叉反应。
