Gutiérrez-Kobeh L, Cabrera N, Pérez-Montfort R
Departamento de Microbiologia, Universidad Nacional Autónoma de México, México, D.F., México.
J Parasitol. 1997 Apr;83(2):234-41.
Some Entamoeba histolytica strains resist complement-mediated lysis by serum. Susceptible and resistant strains activate the complement system equivalently, but resistant amebas evade killing by membrane attack complexes. Our objective was to determine the mechanism by which trophozoites of E. histolytica resist lysis by human serum. Amebas were made resistant to lysis by incubation with increasing concentrations of normal human serum. The possibility that resistant cells ingest membrane attack complexes was explored by subcellular fractionation of susceptible and resistant trophozoites treated with sublytic concentrations of human serum containing radiolabeled C9. In both cases, most of the label was in the fractions containing plasma membrane. The susceptible strain consistently showed more label associated with these fractions than the resistant strain. Thus, the possibility that the membrane attack complexes were released to the medium was explored. Both resistant and susceptible trophozoites release to the medium similar amounts of material excluded by Sepharose CL-2B in the presence or absence of normal human serum. Labeled C9 elutes together with the main bulk of proteins from the medium: this indicates that it is not in vesicles or high molecular weight aggregates. Coincubation of susceptible amebas with lysates of resistant trophozoites confers resistance to susceptible cells within 30 min. Resistance to lysis by serum can also be acquired by susceptible amebas after coincubation with lysates from human erythrocytes or after feeding them with whole human red blood cells. Resistant but not susceptible trophozoites show intense immunofluorescent staining on their surface with anti-human erythrocytic membrane antibody. These results suggest that amebas acquire resistance to lysis by serum by incorporating into their membranes complement regulatory proteins.
一些溶组织内阿米巴菌株可抵抗血清介导的补体溶解作用。敏感菌株和耐药菌株同等程度地激活补体系统，但耐药阿米巴可逃避膜攻击复合物的杀伤作用。我们的目的是确定溶组织内阿米巴滋养体抵抗人血清溶解的机制。通过用浓度递增的正常人血清孵育，使阿米巴对溶解产生抗性。通过对用含放射性标记C9的人血清亚裂解浓度处理的敏感和耐药滋养体进行亚细胞分级分离，探讨了耐药细胞摄取膜攻击复合物的可能性。在这两种情况下，大部分标记物都存在于含有质膜的级分中。与耐药菌株相比，敏感菌株始终显示与这些级分相关的标记物更多。因此，探讨了膜攻击复合物释放到培养基中的可能性。在有或没有正常人血清的情况下，耐药和敏感滋养体释放到培养基中的被琼脂糖CL-2B排除的物质数量相似。标记的C9与培养基中的大部分蛋白质一起洗脱：这表明它不存在于囊泡或高分子量聚集体中。敏感阿米巴与耐药滋养体裂解物共同孵育30分钟内可使敏感细胞产生抗性。敏感阿米巴与人类红细胞裂解物共同孵育或喂食全人类红细胞后，也可获得对血清溶解的抗性。耐药但不敏感的滋养体用抗人红细胞膜抗体处理后，其表面显示强烈的免疫荧光染色。这些结果表明，阿米巴通过将补体调节蛋白整合到其膜中而获得对血清溶解的抗性。
