Reinagel M L, Taylor R P
Department of Biochemistry, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
J Immunol. 2000 Feb 15;164(4):1977-85. doi: 10.4049/jimmunol.164.4.1977.
We are developing a potential therapeutic approach for removing pathogens from the circulation of primates in which the pathogen is bound to the complement receptor (CR1) on E using a bispecific mAb complex, a heteropolymer (HP). We have used mAb this approach to demonstrate that cleared prototype pathogens are localized to, phagocytosed in, and destroyed in the liver. Extension of this work to a clinical setting will require a detailed understanding of the mechanism by which the E-bound immune complex substrates are transferred to fixed tissue macrophages in the liver, the transfer reaction. Therefore, we examined an in vitro system to study this process using bacteriophage phiX174 as a model pathogen. E containing phiX174 (bound via an anti-CR1/anti-phiX174 HP) were incubated with P388D1 murine macrophages, and the two cell types were separated by centrifugation through Ficoll. Both E and macrophages were then probed and analyzed by RIA or flow cytometry. The results indicate that all three components of the E-bound IC (phiX174, HP, and CR1) were removed from the E and internalized by the macrophages. We found that transfer requires the Fc portion of IgG, because little transfer of phiX174 occurs when it is bound to E CR1 using a HP containing only Fab fragments. These findings, taken in the context of other studies, suggest a general mechanism for the transfer reaction in which Fc receptors facilitate close juxtaposition of the macrophage to the E-bound IC which then allows a macrophage-associated protease to cleave CR1. The released IC are then internalized and processed by the macrophages.
我们正在开发一种潜在的治疗方法，用于从灵长类动物的循环系统中清除病原体，该方法是使用双特异性单克隆抗体复合物（一种异聚物，HP）使病原体与红细胞（E）上的补体受体（CR1）结合。我们已使用单克隆抗体通过这种方法证明，被清除的原型病原体定位于肝脏、在肝脏中被吞噬并被破坏。将这项工作扩展到临床环境将需要详细了解与E结合的免疫复合物底物转移至肝脏中固定组织巨噬细胞的机制，即转移反应。因此，我们研究了一种体外系统，以噬菌体phiX174作为模型病原体来研究这一过程。将含有phiX174的E（通过抗CR1/抗phiX174 HP结合）与P388D1鼠巨噬细胞一起孵育，然后通过Ficoll离心分离这两种细胞类型。接着，通过放射免疫分析（RIA）或流式细胞术对E和巨噬细胞进行检测和分析。结果表明，与E结合的免疫复合物的所有三个组分（phiX174、HP和CR1）都从E上被去除并被巨噬细胞内化。我们发现转移需要IgG的Fc部分，因为当使用仅含Fab片段的HP将phiX174与E CR1结合时，phiX174的转移很少发生。结合其他研究来看，这些发现提示了一种转移反应的一般机制，即Fc受体促进巨噬细胞与结合在E上的免疫复合物紧密并列，然后使巨噬细胞相关蛋白酶裂解CR1。释放的免疫复合物随后被巨噬细胞内化并处理。
