Faaber P, Capel P J, Koene R A
Clin Exp Immunol. 1981 Sep;45(3):590-4.
When citrate plasma and serum of the same individual were tested simultaneously in the C1q-binding assay (C1qBA), binding levels in plasma were found to be 90-400% higher than in serum. The difference in 125I-Clq binding was due to the presence of fibrinogen in plasma. It was shown that complex formation between fibrinogen and 125I-Clq occurs and that this complex precipitates in the presence of polyethylene glycol, leading to the false positive results in the ClqBA. When heparin plasma was used to the assay, heparin itself also induced an increase in 125I-C1q binding that was not based on the presence of immune complexes. The effect of both fibrinogen and heparin could be inhibited by addition of protamine sulphate. Therefore, pretreatment of plasma with protamine sulphate makes it possible to use plasma samples for a reliable determination of C1q-binding levels. However, serum that is well clotted should be used preferentially.
当在C1q结合试验（C1qBA）中同时检测同一个体的枸橼酸盐血浆和血清时，发现血浆中的结合水平比血清中的高90 - 400%。125I-Clq结合的差异是由于血浆中存在纤维蛋白原。结果表明，纤维蛋白原与125I-Clq之间会形成复合物，并且该复合物在聚乙二醇存在的情况下会沉淀，从而导致C1qBA出现假阳性结果。当使用肝素血浆进行该试验时，肝素本身也会导致125I-C1q结合增加，而这并非基于免疫复合物的存在。硫酸鱼精蛋白的添加可以抑制纤维蛋白原和肝素的作用。因此，用硫酸鱼精蛋白对血浆进行预处理可以使血浆样本用于可靠地测定C1q结合水平。然而，应优先使用充分凝固的血清。
