Arvieux J, Reboul A, Bensa J C, Colomb M G
Biochem J. 1984 Mar 1;218(2):547-55. doi: 10.1042/bj2180547.
The binding of C1q to the human macrophage cell line U937 has been studied. Fluorescence microscopy with fluorescein-conjugated F(ab')2 anti-C1q antibody showed that 100% of the cell population is able to bind exogenous C1q. Monomeric C1q binding to U937 cells is very weak at normal ionic strength (I0.15) and was therefore investigated at I0.07, conditions which stabilize the binding. However, aggregation of C1q on dextran sulphate or a lipid A-rich lipopolysaccharide allowed a firm, binding at I0.15. Quantitative binding studies with monomeric 125I-C1q showed a concentration-dependent, saturable, specific and reversible binding involving specific membrane receptors. Scatchard plots of C1q binding indicated [1.6 +/- 0.7 (1 S.D.)] X 10(6) sites per cell with an equilibrium constant of (2.9 +/- 1.8) X 10(7) M-1 at I0.07. The location of the molecule region mediating C1q binding was established with collagen-like fragments prepared by partial pepsin digestion, confirming earlier results obtained by inhibition studies.
已经对C1q与人巨噬细胞系U937的结合进行了研究。用荧光素偶联的F(ab')2抗C1q抗体进行荧光显微镜检查表明，100%的细胞群体能够结合外源性C1q。在正常离子强度（I0.15）下，单体C1q与U937细胞的结合非常弱，因此在I0.07（稳定结合的条件）下进行了研究。然而，C1q在硫酸葡聚糖或富含脂质A的脂多糖上的聚集允许在I0.15下牢固结合。用单体125I-C1q进行的定量结合研究表明，存在涉及特定膜受体的浓度依赖性、可饱和、特异性和可逆结合。C1q结合的Scatchard图表明，在I0.07时，每个细胞有[1.6±0.7（1个标准差）]×10(6)个位点，平衡常数为(2.9±1.8)×10(7) M-1。通过部分胃蛋白酶消化制备的胶原样片段确定了介导C1q结合的分子区域的位置，证实了早期通过抑制研究获得的结果。
