Gordon D L, Johnson G M, Hostetter M K
Immunology. 1987 Apr;60(4):553-8.
We determined in binding assays using monomeric fluid-phase iC3b and Scatchard analysis that iC3b binds to human polymorphonuclear leucocyte type 3 complement receptor (CR3), a low-density/high-affinity receptor (28,200 binding sites, affinity constant (Ka) = 2.1 +/- 0.47 X 10(6) L/M), and to the C3b receptor (CR1), a high-density/low-affinity receptor (54,700 binding sites, Ka = 1.7 +/- 2.04 X 10(5) L/M. Binding of iC3b to CR1 was confirmed by blocking experiments with polyclonal F(ab')2 antibody against CR1, and competitive binding experiments with C3b. Binding of iC3b to CR3 was demonstrated by blocking experiments with the monoclonal antibody OKM10 against the ligand binding site of CR3. Inhibition of both CR1 and CR3 did not completely reduce iC3b binding, indicating the existence of additional iC3b-binding sites on PMN. Using flow cytometric analysis of receptor expression, no positive or negative co-operativity was observed between CR1 and CR3. Expression of both receptors increased in a dose-dependent manner after incubation with f-met-leu-phe or phorbol myristate acetate; however, only CR3 expression was enhanced at very low concentrations of these stimuli. iC3b/CR3 interactions probably play a central role in host defence against microorganisms.
我们在使用单体液相iC3b的结合试验及Scatchard分析中确定，iC3b可与人多形核白细胞3型补体受体（CR3，一种低密度/高亲和力受体，有28,200个结合位点，亲和常数（Ka）=2.1±0.47×10⁶ L/M）以及C3b受体（CR1，一种高密度/低亲和力受体，有54,700个结合位点，Ka = 1.7±2.04×10⁵ L/M）结合。用抗CR1的多克隆F(ab')₂抗体进行阻断实验以及用C3b进行竞争性结合实验，证实了iC3b与CR1的结合。用抗CR3配体结合位点的单克隆抗体OKM10进行阻断实验，证明了iC3b与CR3的结合。对CR1和CR3的抑制并未完全降低iC3b的结合，这表明多形核白细胞上存在其他iC3b结合位点。通过流式细胞术分析受体表达，未观察到CR1和CR3之间存在正协同或负协同作用。用f-甲硫氨酰-亮氨酰-苯丙氨酸或佛波醇肉豆蔻酸酯孵育后，两种受体的表达均呈剂量依赖性增加；然而，在这些刺激物的极低浓度下，只有CR3的表达增强。iC3b/CR3相互作用可能在宿主抵御微生物的防御中起核心作用。
