Mosser D M, Wedgwood J F, Edelson P J
J Immunol. 1985 Jun;134(6):4128-31.
Amastigote forms of Leishmania major are sensitive to lysis by fresh serum, whereas those of L. donovani are resistant. To understand the basis for this resistance we have examined the interaction of complement with amastigotes of seven strains of leishmania. Complement activation was determined by measuring the ability of amastigotes to consume complement from normal serum and by identifying parasite surface-bound C3. All of the strains that were tested activated complement, including both those that are resistant and those that are susceptible to inactivation by fresh serum. Complement consumption by amastigotes was measured as a decrease in the ACH 50 titers of serum exposed to parasites. L. major, L. donovani, and L. mexicana mexicana (strain 1VLM) amastigotes decrease titers by 35.7, 33.5, and 40.3%, respectively. The binding of C3 to amastigotes was judged qualitatively by immunofluorescence and quantitatively by a C3 radiobinding assay. L. major amastigotes bind an average of 6.6 X 10(4) molecules of C3 per parasite. L. mexicana amazonensis, L. mexicana mexicana, and L. donovani bind an average of 3.9 X 10(4), 5.9 X 10(4), and 3.7 X 10(4) molecules, respectively. In all cases, C3 binding is the result of alternative pathway activation requiring Mg++ but not Ca++. Amastigotes of the disseminating strains of leishmania represent the first example of a group of protozoa that activate early complement components leading to fixation of C3, but that are resistant to inactivation by complement.
硕大利什曼原虫的无鞭毛体形式对新鲜血清的溶解敏感，而杜氏利什曼原虫的无鞭毛体则具有抗性。为了解这种抗性的基础，我们研究了补体与七种利什曼原虫菌株的无鞭毛体之间的相互作用。通过测量无鞭毛体从正常血清中消耗补体的能力以及鉴定寄生虫表面结合的C3来确定补体激活。所有测试的菌株都激活了补体，包括那些具有抗性的菌株和那些对新鲜血清灭活敏感的菌株。无鞭毛体消耗补体的量通过测定暴露于寄生虫的血清的ACH 50滴度的降低来衡量。硕大利什曼原虫、杜氏利什曼原虫和墨西哥利什曼原虫（1VLM株）的无鞭毛体分别使滴度降低35.7%、33.5%和40.3%。通过免疫荧光定性判断C3与无鞭毛体的结合，并通过C3放射结合试验进行定量。硕大利什曼原虫的无鞭毛体每个寄生虫平均结合6.6×10⁴个C3分子。亚马逊利什曼原虫、墨西哥利什曼原虫和杜氏利什曼原虫分别平均结合3.9×10⁴、5.9×10⁴和3.7×10⁴个分子。在所有情况下，C3结合是替代途径激活的结果，需要Mg²⁺但不需要Ca²⁺。利什曼原虫传播菌株的无鞭毛体代表了一组原生动物的第一个例子，这些原生动物激活早期补体成分导致C3固定，但对补体灭活具有抗性。
