Heinz H P, Burger R, Golan M D, Loos M
J Immunol. 1984 Feb;132(2):804-8.
The effect of a purified monoclonal anti-C1q anti-body (Ab 242 G3) on the function of C1q, a subcomponent of the first component of complement C1, was studied. No inhibition of purified activated C1 was observed, whereas binding of the Ab to fluid phase C1q, to C1q bound to immune complexes (EAC1q), or to serum C1 in fluid phase resulted in a dose-dependent inhibition of the hemolytic activity of C1. In contrast, when the effect of the Ab on serum C1 bound to immune complexes (EAC1) was measured, no inhibition, but a dose-dependent enhancement, of the hemolytic activity was obtained. The dose-response curve of the Ab-treated cell-bound serum C1 was indistinguishable from that of activated C1. Isolated Fab fragments of this Ab did not cause an increase in C1 activity. After separation of the A, B, and C chains of C1q by SDS-PAGE, Ab 242 G3 reacted in immunoblotting selectively with the C chain. These data indicate that cross-linking of C1q via the C chain of C1q might lead to an internal activation of C1.
研究了纯化的单克隆抗C1q抗体（Ab 242 G3）对补体C1第一成分的亚成分C1q功能的影响。未观察到对纯化的活化C1的抑制作用，而该抗体与液相C1q、与结合在免疫复合物上的C1q（EAC1q）或液相血清C1的结合导致C1溶血活性呈剂量依赖性抑制。相反，当测量该抗体对结合在免疫复合物上的血清C1（EAC1）的作用时，未观察到抑制作用，反而获得了溶血活性的剂量依赖性增强。经该抗体处理的细胞结合血清C1的剂量反应曲线与活化C1的曲线无法区分。该抗体的分离Fab片段未引起C1活性增加。通过SDS-PAGE分离C1q的A、B和C链后，Ab 242 G3在免疫印迹中与C链选择性反应。这些数据表明，通过C1q的C链对C1q进行交联可能导致C1的内部活化。
