Kierszenbaum F, Ramirez M A
Department of Microbiology and Public Health, Michigan State University, East Lansing 48824-1101.
Infect Immun. 1990 Jan;58(1):119-23. doi: 10.1128/iai.58.1.119-123.1990.
The numerous reports on lysis of blood (trypomastigote) forms of Trypanosoma cruzi by specific antibodies plus complement have systematically shown that a certain proportion of parasites survives. However, it is not known whether the insensitive organisms represent a subpopulation (or clones) or a certain developmental phase of otherwise morphologically identical parasites. In this work, we established that partial lysis was not due to the use of insufficient amounts of lytic reagents. Thus, supernatants of lytic reaction mixtures killed the same proportion of T. cruzi as previously unused reagents. Moreover, in parallel tests in which the trypomastigote concentration was up to four times greater than that used in standard lysis tests, the percentages of lysis were comparable. Incubation periods as long as 4 h did not increase the extent of lysis beyond the value observed after only 1 h, indicating that the routinely used 1-h incubation was appropriate. The extent of lysis was not increased by additional amounts of antibody, complement, or both. Instead, trypomastigotes surviving immune lysis, washed, and incubated with fresh diluent for 45 to 120 min before being used in new lysis tests did manifest additional sensitivity to immune lysis. Three successive infections in mice with parasites which had survived immune lysis led to the production of trypanosomes that displayed the same level of resistance to immune lysis as the original, untreated parasite population. Of interest, the average parasitemias of these groups of mice did not evidence a tendency to increase, as might have occurred if an immune-lysis-resistant subpopulation had been selected. Since trypomastigotes exhibiting resistance to immune lysis can eventually become sensitive, resistance to immune lysis does not represent an insensitive parasite subpopulation. This resistance appears to be modulated by the presence of the lytic reagents and might involve expression of as yet unidentified surface components playing a role in complement activation.
关于特异性抗体加补体对克氏锥虫血液（锥鞭毛体）形态的裂解作用，众多报告系统地表明一定比例的寄生虫能够存活。然而，尚不清楚这些不敏感的生物体是代表一个亚群（或克隆），还是形态上相同的寄生虫的某个发育阶段。在这项研究中，我们确定部分裂解并非由于使用了不足量的裂解试剂。因此，裂解反应混合物的上清液杀死克氏锥虫的比例与先前未使用的试剂相同。此外，在平行试验中，锥鞭毛体浓度比标准裂解试验中使用的浓度高至四倍，裂解百分比仍具有可比性。长达4小时的孵育期并未使裂解程度超过仅1小时后观察到的值，这表明常规使用的1小时孵育是合适的。额外增加抗体、补体或两者的量并不会增加裂解程度。相反，经免疫裂解存活的锥鞭毛体，洗涤后与新鲜稀释液孵育45至120分钟，然后用于新的裂解试验，确实表现出对免疫裂解的额外敏感性。用经免疫裂解存活的寄生虫连续三次感染小鼠，导致产生的锥虫对免疫裂解的抗性水平与原始未处理的寄生虫群体相同。有趣的是，这些小鼠组的平均寄生虫血症并未显示出增加的趋势，而如果选择了抗免疫裂解的亚群可能会出现这种情况。由于对免疫裂解表现出抗性的锥鞭毛体最终可能会变得敏感，因此对免疫裂解的抗性并不代表不敏感的寄生虫亚群。这种抗性似乎受到裂解试剂存在的调节，可能涉及尚未鉴定的表面成分的表达，这些成分在补体激活中起作用。
