Michael J M, Moore J A, Chaplin H
Transfusion. 1976 Sep-Oct;16(5):408-16. doi: 10.1046/j.1537-2995.1976.16577039294.x.
Test erythrocytes (E) used to evaluate anti-complement (C') antiglobulin sera have not been adequately standardized. This report describes a previously unrecognized C4-derived antigen (temporarily called X-Ag) found on E generally believed to be coated only with the C3d subcomponent of C3, X-Ag occurred on all E coated in vitro with C' by low ionic strength-sucrose or cold agglutinin methods and on E from ten of ten patients whose cells had been C' coated in vivo. It was not removed by incubating these cells with trypsin or fresh compatible serum. This antigen was found on "C4-only-coated" red blood cells made with normal or congenitally C2-deficient serum but not on cells similarly prepared with congenitally C4-deficient serum. It was not identified on E coated with C' via the alternate pathway, normal trypsinized cells, nor cells coated only with IgG. Absorption experiments utilizing purified complement components and subcomponents and G200 Sephadex fractions of normal human serum strongly suggest that X-Ag is a subcomponent of C4(C4d). These results show that at least one C' subcomponent other than C3d occures on both in vitro and in vivo C3d-coated erythrocytes and must be taken into account when such cells are used to evaluate antiglobulin reagents.
用于评估抗补体（C'）抗球蛋白血清的试验红细胞（E）尚未得到充分标准化。本报告描述了一种以前未被识别的C4衍生抗原（暂称为X抗原），该抗原在通常认为仅被C3的C3d亚组分包被的E上被发现。X抗原出现在所有通过低离子强度蔗糖法或冷凝集素法在体外被C'包被的E上，以及出现在其细胞在体内已被C'包被的10名患者的所有E上。用胰蛋白酶或新鲜的相容血清孵育这些细胞并不能去除该抗原。在由正常血清或先天性C2缺陷血清制备的“仅被C4包被”的红细胞上发现了这种抗原，但在由先天性C4缺陷血清类似制备的细胞上未发现。在通过替代途径被C'包被的E、正常胰蛋白酶处理的细胞或仅被IgG包被的细胞上未鉴定出该抗原。利用纯化的补体成分和亚成分以及正常人血清的G200葡聚糖凝胶级分进行的吸收实验强烈表明，X抗原是C4（C4d）的一种亚成分。这些结果表明，除C3d外，至少一种C'亚成分出现在体外和体内被C3d包被的红细胞上，并且在使用此类细胞评估抗球蛋白试剂时必须予以考虑。
