Cooper K M, Moore M
J Immunol Methods. 1983 Jun 10;60(3):289-303. doi: 10.1016/0022-1759(83)90287-9.
Treatment of artificial immune complexes (ICs) with 2.5% polyethylene glycol (PEG)--conditions under which C1q-binding activity is routinely measured in the fluid phase--produced marked changes in molecular size as determined by Sepharose 6B chromatography. The effect of PEG on the C1q-binding capacity of ICs, was therefore investigated using a solid phase (SP) system. PEG enhanced the binding of aggregated human gammaglobulin (AHG) and artificial ICs to SP-C1q and, in reverse experiments, also increased the binding of C1q to SP-AHG. The degree of enhancement varied according to the Ag:Ab ratio employed; the binding of ICs formed in moderate Ab excess was only modestly enhanced but that of complexes formed at slight Ab excess, equivalence and Ag excess was markedly elevated. The profile of PEG-induced enhancement of binding paralleled that of similar ICs in the C1q fluid phase system, suggesting that C1q binding in the latter may be influenced by PEG. However, the C1q-binding activity of in vivo-formed ICs seemed to be relatively unaffected by PEG since enhanced binding was comparable in control and pathological sera. The results indicate that PEG causes cross-linking and aggregation of ICs (and possibly other serum proteins) which may alter their biological activity and hence influence the results of IC assays that employ this agent.
用2.5%聚乙二醇（PEG）处理人工免疫复合物（ICs）——在该条件下通常在液相中测定C1q结合活性——通过琼脂糖6B层析测定，分子大小发生了显著变化。因此，使用固相（SP）系统研究了PEG对ICs的C1q结合能力的影响。PEG增强了聚集的人γ球蛋白（AHG）和人工ICs与固相C1q的结合，在反向实验中，也增加了C1q与固相AHG的结合。增强程度根据所用的抗原：抗体比例而有所不同；在抗体中度过量时形成的ICs的结合仅略有增强，但在抗体轻度过量、等价和抗原过量时形成的复合物的结合则显著升高。PEG诱导的结合增强曲线与C1q液相系统中类似ICs的曲线平行，表明后者中的C1q结合可能受PEG影响。然而，体内形成的ICs的C1q结合活性似乎相对不受PEG影响，因为在对照血清和病理血清中增强的结合相当。结果表明，PEG导致ICs（可能还有其他血清蛋白）交联和聚集，这可能改变它们的生物学活性，从而影响使用该试剂的IC检测结果。
