Carter R H, Spycher M O, Ng Y C, Hoffman R, Fearon D T
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
J Immunol. 1988 Jul 15;141(2):457-63.
We sought biochemical evidence for a role of C receptors types 1 (CR1) and 2 (CR2) in B cell activation. A flow cytometer was used to measure the fluorescence of tonsillar cells that had been loaded with the calcium-dependent indicator indo-1, and cells were stimulated by cross-linking cell-bound DA4.4 anti-IgM, Yz-1 anti-CR1 or HB5 anti-CR2 with goat anti-mouse IgG. There was a direct dose-response relationship between the proportion of cells having increased cytoplasmic free calcium concentration (Cai) after addition of second antibody and the amount of cell-bound Fab' DA4.4. In contrast, no rise in Cai was observed after cross-linking bound Yz-1 or HB5. To determine whether CR1 or CR2 could modify the increase in Cai induced by cross-linking membrane IgM, Cai was monitored after addition of second antibody to cells bearing combinations of either Yz-1 or HB5 with a limited amount of DA4.4. The combination of Yz-1 with DA4.4 yielded little or no further increase in the percentage of cells responding to cross-linking with elevated Cai compared with DA4.4 alone. However, the combination of HB5 with limited DA4.4 synergistically enhanced this response, resulting in stimulation that was equivalent to that obtained with optimal concentrations of DA4.4. The synergistic effect of CR2 was also observed with avidin as the cross-linking reagent for bound biotinylated HB5 and DA4.4, occurred in the presence of EGTA, and did not require T cells. Studies of the proliferation of B cell-enriched PBMC demonstrated that, whereas HB5 coupled to Sepharose alone induced little or no DNA synthesis, the combination of HB5 with limited DA4.4 on Sepharose induced a dose-related synergistic increase in the incorporation of [3H]thymidine.
我们探寻了1型补体受体（CR1）和2型补体受体（CR2）在B细胞活化中发挥作用的生化证据。使用流式细胞仪测量已加载钙依赖性指示剂indo-1的扁桃体细胞的荧光，通过用山羊抗小鼠IgG交联细胞结合的DA4.4抗IgM、Yz-1抗CR1或HB5抗CR2来刺激细胞。添加二抗后细胞质游离钙浓度（Cai）升高的细胞比例与细胞结合的Fab' DA4.4量之间存在直接的剂量反应关系。相比之下，交联结合的Yz-1或HB5后未观察到Cai升高。为了确定CR1或CR2是否可以改变交联膜IgM诱导的Cai增加，在向携带Yz-1或HB5与有限量DA4.4组合的细胞中添加二抗后监测Cai。与单独使用DA4.4相比，Yz-1与DA4.4的组合导致对交联反应且Cai升高的细胞百分比几乎没有进一步增加或没有增加。然而，HB5与有限量DA4.4的组合协同增强了这种反应，导致刺激效果等同于用最佳浓度的DA4.4所获得的刺激效果。当使用抗生物素蛋白作为结合的生物素化HB5和DA4.4的交联剂时，也观察到了CR2的协同作用，该作用在EGTA存在的情况下发生，并且不需要T细胞。对富含B细胞的外周血单核细胞增殖的研究表明，单独与琼脂糖偶联的HB5几乎不诱导或不诱导DNA合成，而琼脂糖上HB5与有限量DA4.4的组合诱导[3H]胸苷掺入呈剂量相关的协同增加。
