Alcolea J M, Antón L C, Marqués G, Sánchez-Corral P, Vivanco F
Complement. 1987;4(1):21-32. doi: 10.1159/000463004.
The binding properties of activated C4 to immune complexes (ovalbumin-rabbit IgG antiovalbumin) were studied by using 125I-IgG in the immune complexes or performing the C4 binding assays in the presence of 14C-iodoacetamide. High molecular weight complexes formed between C4 and IgG could be detected by the incorporation of 14C-iodoacetamide in the -SH group generated in the nascent C4b during the activation process. The same complexes with an apparent molecular weight of 180,000 daltons were detected when the immune aggregates contained 125I-IgG. Two-dimensional SDS-PAGE analysis of the C4b-IgG covalent complexes indicated: In the absence of control proteins, the complexes are formed by the alpha'-chain of C4b and the H chain of the antibody. The alpha'-H complexes are 36% sensitive to hydroxylamine and 64% resistant. This is consistent with the presence of two populations of C4, which are not equivalent in their covalent binding with immune complexes. Covalent complexes C4-C4b or C4b(like)-C4b(like) are generated during the C4 activation and they are detected as alpha-alpha' or alpha-alpha complexes, respectively. Interaction of C4b with the L chain of the antibody molecule also seems to occur, but to a lesser extent than with the H chain.
通过在免疫复合物中使用125I-IgG或在14C-碘乙酰胺存在下进行C4结合试验，研究了活化的C4与免疫复合物（卵清蛋白-兔IgG抗卵清蛋白）的结合特性。在活化过程中，新生C4b中产生的-SH基团中掺入14C-碘乙酰胺，可检测到C4与IgG之间形成的高分子量复合物。当免疫聚集体含有125I-IgG时，检测到同样表观分子量为180,000道尔顿的复合物。对C4b-IgG共价复合物进行二维SDS-PAGE分析表明：在没有对照蛋白的情况下，复合物由C4b的α'-链和抗体的重链形成。α'-H复合物对羟胺的敏感性为36%，抗性为64%。这与存在两种C4群体一致，它们与免疫复合物的共价结合并不等同。在C4活化过程中产生共价复合物C4-C4b或C4b(样)-C4b(样)，分别检测为α-α'或α-α复合物。C4b与抗体分子轻链的相互作用似乎也会发生，但程度小于与重链的相互作用。
