Aga Eresso, Katschinski Dörthe M, van Zandbergen Ger, Laufs Helmut, Hansen Birgit, Müller Kerstin, Solbach Werner, Laskay Tamás
Institute for Medical Microbiology and Hygiene, Medical University of Lübeck, Lübeck, Germany.
J Immunol. 2002 Jul 15;169(2):898-905. doi: 10.4049/jimmunol.169.2.898.
Macrophages are the major target cell population of the obligate intracellular parasites Leishmania. Although polymorphonuclear neutrophil granulocytes (PMN) are able to internalize Leishmania promastigotes, these cells have not been considered to date as host cells for the parasites, primarily due to their short life span. In vitro coincubation experiments were conducted to investigate whether Leishmania can modify the spontaneous apoptosis of human PMN. Coincubation of PMN with Leishmania major promastigotes resulted in a significant decrease in the ratio of apoptotic neutrophils as detected by morphological analysis of cell nuclei, TUNEL assay, gel electrophoresis of low m.w. DNA fragments, and annexin V staining. The observed antiapoptotic effect was found to be associated with a significant reduction of caspase-3 activity in PMN. The inhibition of PMN apoptosis depended on viable parasites because killed Leishmania or a lysate of the parasites did not have antiapoptotic effect. L. major did not block, but rather delayed the programmed cell death of neutrophils by approximately 24 h. The antiapoptotic effect of the parasites could not be transferred by the supernatants, despite secretion of IL-8 by PMN upon coculture with L. major. In vivo, intact parasites were found intracellularly in PMN collected from the skin of mice 3 days after s.c. infection. This finding strongly suggests that infection with Leishmania prolongs the survival time of neutrophils also in vivo. These data indicate that Leishmania induce an increased survival of neutrophil granulocytes both in vitro and in vivo.
巨噬细胞是专性细胞内寄生虫利什曼原虫的主要靶细胞群体。尽管多形核中性粒细胞（PMN）能够内化利什曼原虫前鞭毛体，但由于其寿命较短，这些细胞至今未被视为该寄生虫的宿主细胞。进行了体外共孵育实验，以研究利什曼原虫是否能改变人PMN的自发凋亡。通过细胞核形态分析、TUNEL检测、低分子量DNA片段凝胶电泳和膜联蛋白V染色检测发现，PMN与硕大利什曼原虫前鞭毛体共孵育导致凋亡中性粒细胞的比例显著降低。观察到的抗凋亡作用与PMN中caspase-3活性的显著降低有关。PMN凋亡的抑制取决于活的寄生虫，因为杀死的利什曼原虫或其裂解物没有抗凋亡作用。硕大利什曼原虫并未阻止，而是将中性粒细胞的程序性细胞死亡延迟了约24小时。尽管PMN与硕大利什曼原虫共培养时会分泌IL-8，但寄生虫的抗凋亡作用不能通过上清液传递。在体内，皮下感染3天后从小鼠皮肤收集的PMN细胞内发现了完整的寄生虫。这一发现有力地表明，利什曼原虫感染也能在体内延长中性粒细胞的存活时间。这些数据表明，利什曼原虫在体外和体内均可诱导中性粒细胞存活率增加。
