Tarleton R L, Kemp W M
J Immunol. 1981 Jan;126(1):379-84.
Previous studies have indicated that adult schistosomes have an affinity for both IgG and C; however, thorough investigations on the possible presence of receptors for these serum proteins on the adult schistosome tegument have not been attempted. The present study presents evidence for both IgG-Fc and C3 receptors on adult schistosomes. An indirect assay utilizing fluoresceinated Staphylococcus aureus was developed to detect antigen-antibody (Ag-Ab) and antigen-antibody-C (Ag-Ab-C) binding to adult parasites. Detection of Ag-Ab and Ag-Ab-C complex binding was dependent on the presence of a metabolic inhibitor in the incubation mixture presumably to prevent shedding of bound complexes. Ag-Ab complex binding required the presence of an intact Fc on the IgG of the complex and could be partially inhibited by preincubation of parasites in heat-aggregated IgG or an isolated Fc preparation. Binding of Ag-Ab-C complexes was dependent on active C3 in the C source but not on an intact Fc on the IgG of the complex. Ag-Ab-C binding could be blocked by prior incubation of parasites in heat-aggregated IgG-C but not by C alone. Binding of host serum proteins to IgG-Fc and C3 receptors on adult schistosomes may aid parasite survival by helping to prevent immune detection.
以往的研究表明，成年血吸虫对IgG和补体C都有亲和力；然而，尚未尝试对成年血吸虫体表上这些血清蛋白的受体可能存在情况进行全面研究。本研究提供了成年血吸虫存在IgG-Fc和C3受体的证据。开发了一种利用荧光标记金黄色葡萄球菌的间接检测方法，以检测抗原-抗体（Ag-Ab）和抗原-抗体-补体C（Ag-Ab-C）与成年寄生虫的结合。Ag-Ab和Ag-Ab-C复合物结合的检测取决于孵育混合物中代谢抑制剂的存在，推测这是为了防止结合复合物的脱落。Ag-Ab复合物的结合需要复合物IgG上存在完整的Fc，并且可以通过在热聚集IgG或分离的Fc制剂中预孵育寄生虫来部分抑制。Ag-Ab-C复合物的结合取决于补体C来源中的活性C3，但不取决于复合物IgG上的完整Fc。Ag-Ab-C的结合可以通过在热聚集IgG-C中预孵育寄生虫来阻断，但单独的补体C不能阻断。宿主血清蛋白与成年血吸虫上的IgG-Fc和C3受体的结合可能通过帮助防止免疫检测来辅助寄生虫存活。
