Hoover D L, Berger M, Oppenheim M H, Hockmeyer W T, Meltzer M S
Infect Immun. 1985 Jan;47(1):247-52. doi: 10.1128/iai.47.1.247-252.1985.
Mechanisms that mediate recovery from leishmanial infection have not been fully characterized but are generally believed to involve interactions between T lymphocytes and macrophages. A major role for serum-mediated effector mechanisms in the protection of humans from reinfection with Leishmania, however, has not been ruled out. In this report, amastigotes of L. donovani were incubated with dilutions of serum from normal subjects and from patients with kala-azar. Normal serum was cytotoxic for parasites at a dilution of greater than or equal to 1:20. Cytotoxicity did not occur in the presence of EDTA, was abolished by heating serum to 56 degrees C for 30 min, and was not diminished by prior adsorption of normal serum with parasites at 0 degree C. Killing proceeded normally in the presence of magnesium-ethylene glycol-bis(beta-aminoethyl ether)-N, N-tetraacetic acid, however, and was fully effected by C2-deficient serum. These studies indicated that killing of amastigotes, unlike that of promastigotes, was mediated via the alternate pathway of serum complement. In further studies, cytotoxicity of normal serum was enhanced three- to fivefold by factors in patient serum. This enhanced cytotoxicity also proceeded via the alternate complement pathway. Factors that enhanced cytotoxicity were characterized as parasite-specific immunoglobulin G: they eluted with immunoglobulin G on column chromatography, were adsorbed by immobilized staphylococcal protein A, and were not removed from the parasite surface by extensive washing. Thus, infection of individuals with L. donovani resulted in the production of a new, qualitatively and quantitatively distinct immune mechanism directed against the amastigote form of the parasite, namely, antibody-directed, alternate complement pathway-mediated cytotoxicity. These results provide a mechanistic framework for a role of humoral factors in human resistance to reinfection with L. donovani.
介导利什曼原虫感染恢复的机制尚未完全明确，但一般认为涉及T淋巴细胞与巨噬细胞之间的相互作用。然而，血清介导的效应机制在保护人类免受利什曼原虫再次感染中的主要作用尚未被排除。在本报告中，将杜氏利什曼原虫无鞭毛体与正常受试者和黑热病患者的血清稀释液一起孵育。正常血清在稀释度大于或等于1:20时对寄生虫具有细胞毒性。在存在乙二胺四乙酸（EDTA）的情况下不发生细胞毒性，将血清加热至56℃ 30分钟可消除细胞毒性，并且在0℃用寄生虫预先吸附正常血清不会降低细胞毒性。然而，在存在镁-乙二醇双（β-氨基乙基醚）-N，N-四乙酸的情况下杀伤正常进行，并且完全由C2缺陷血清实现。这些研究表明，与前鞭毛体不同，无鞭毛体的杀伤是通过血清补体的替代途径介导的。在进一步的研究中，患者血清中的因子使正常血清的细胞毒性增强了三到五倍。这种增强的细胞毒性也通过替代补体途径进行。增强细胞毒性的因子被鉴定为寄生虫特异性免疫球蛋白G：它们在柱色谱上与免疫球蛋白G一起洗脱，被固定化葡萄球菌蛋白A吸附，并且通过大量洗涤不会从寄生虫表面去除。因此，杜氏利什曼原虫感染个体导致产生一种针对寄生虫无鞭毛体形式的新的、在质量和数量上均不同的免疫机制，即抗体介导的、替代补体途径介导的细胞毒性。这些结果为体液因子在人类抵抗杜氏利什曼原虫再次感染中的作用提供了一个机制框架。
