Russell D G
Eur J Biochem. 1987 Apr 1;164(1):213-21. doi: 10.1111/j.1432-1033.1987.tb11013.x.
The interaction between Leishmania promastigotes and their vertebrate host's complement system results not only in parasite lysis but also, due to surface-bound complement components, in increased macrophage binding potential. In this study we demonstrate, with the use of isolated complement components, that activation is via the alternative complement pathway, initiated by direct deposition of C3 onto the parasite surface. The predominant C3 acceptor site on the promastigotes was initially identified as the glycoprotein gp63 by anti-C3 antibody immunoprecipitation of radioiodinated promastigotes following incubation in the alternative pathway initiators C3, and factors B and D. The C3-binding properties of gp63 were confirmed and quantified, in relation to other surface antigens, by incubating parasites in iodinated C3 and immunoprecipitating bound C3 with antibodies directed against different promastigote surface antigens. The other abundant surface antigen, the glycolipid 'excreted factor', did not show any C3-binding activity. Further demonstration was provided by incubating liposomes containing either gp63 or excreted factor in iodinated C3 and factors B and D. Only gp63-containing liposomes bound C3. Considering that both gp63 and the excreted factor have recently been implicated in attachment and uptake by macrophage, these findings may have considerable bearing in the determination of which of the macrophage surface receptors identify which parasite ligand.
利什曼原鞭毛体与其脊椎动物宿主的补体系统之间的相互作用不仅导致寄生虫裂解，而且由于表面结合的补体成分，还会增加巨噬细胞的结合潜力。在本研究中，我们使用分离的补体成分证明，激活是通过替代补体途径进行的，由C3直接沉积在寄生虫表面引发。在替代途径启动剂C3、因子B和D中孵育后，通过抗C3抗体对放射性碘化前鞭毛体进行免疫沉淀，最初将前鞭毛体上主要的C3受体位点鉴定为糖蛋白gp63。通过在碘化C3中孵育寄生虫并用针对不同前鞭毛体表面抗原的抗体免疫沉淀结合的C3，相对于其他表面抗原，证实并定量了gp63的C3结合特性。另一种丰富的表面抗原，糖脂“排泄因子”，未显示任何C3结合活性。通过在碘化C3、因子B和D中孵育含有gp63或排泄因子的脂质体提供了进一步的证明。只有含有gp63的脂质体结合C3。鉴于gp63和排泄因子最近都与巨噬细胞的附着和摄取有关，这些发现可能对确定哪些巨噬细胞表面受体识别哪些寄生虫配体具有重要意义。
