Stewart W W, Johnson A, Steward M W, Whaley K, Kerr M A
Department of Pathology, University of Dundee, Ninewells Hospital and Medical School, U.K.
Mol Immunol. 1988 Dec;25(12):1355-61. doi: 10.1016/0161-5890(88)90051-x.
Radioimmunoassays for C3a and C4a have been used to measure the activation of complement in human serum by immune complexes containing DNP-BSA and each of 11 mouse anti-DNP monoclonal antibodies of varied isotype and affinity. When preformed complexes were added to serum, those containing IgG2 or IgM were potent activators of C4, whilst IgG1 complexes were less efficient. C3 activation in normal serum was similar for complexes containing IgG1, IgG2a, IgG2b or IgM. IgA complexes did not activate C3 or C4. Solubilisation of complexes was greatest for IgM and IgG2b and least for IgG2a and IgA. In serum containing Mg2+ EGTA C4 activation was abolished and the amount of C3 activation was lower for all IgG and IgM complexes. Antibodies of the same isotype did not necessarily activate complement to the same extent. Unexpectedly, three of the four IgMs activated C3 in EGTA. For IgMs, neither complement activation nor solubilisation correlated with affinity. For IgG1 antibodies, solubilisation was inversely proportional to affinity. C3 or C4 activation did not correlate with affinity.
已采用针对C3a和C4a的放射免疫测定法，来检测含二硝基苯-牛血清白蛋白（DNP-BSA）以及11种不同同种型和亲和力的小鼠抗DNP单克隆抗体中的每一种的免疫复合物对人血清中补体的激活作用。当将预先形成的复合物添加到血清中时，含IgG2或IgM的复合物是C4的强效激活剂，而IgG1复合物的效率较低。含IgG1、IgG2a、IgG2b或IgM的复合物在正常血清中的C3激活作用相似。IgA复合物不激活C3或C4。复合物的溶解情况在IgM和IgG2b中最为显著，在IgG2a和IgA中最不明显。在含有Mg2+ 乙二醇双四乙酸（EGTA）的血清中，C4激活作用被消除，并且所有IgG和IgM复合物的C3激活量均较低。同种型相同的抗体不一定会以相同程度激活补体。出乎意料的是，四种IgM中的三种在EGTA中激活了C3。对于IgM而言，补体激活和溶解均与亲和力无关。对于IgG1抗体，溶解与亲和力成反比。C3或C4激活与亲和力无关。
