Abou Fakher Faihaa Hkima, Rachinel Nicolas, Klimczak Martine, Louis Jacques, Doyen Noëlle
Unité des Réponses Précoces aux Parasites et Immunopathologie, Département de Parasitologie et Mycologie, Institut Pasteur, Paris, France.
J Immunol. 2009 Feb 1;182(3):1386-96. doi: 10.4049/jimmunol.182.3.1386.
In its vertebrate host, Leishmania encounters cells that express TLRs. Using genetically resistant C57BL/6 mice deficient in either TLR2, 4, or 9, we show in this study that only TLR9-deficient mice are more susceptible to infection with Leishmania major. TLR9-deficient mice resolved their lesions and controlled parasites growth with much lower efficiency than wild-type C57BL/6 mice. The absence of TLR9 also transiently inhibited the development of curative Th1 response. In an attempt to analyze the possible basis for such aberrant response in TLR9(-/-) mice, we have studied the importance of TLR9 for the activation of dendritic cells (DCs) by L. major. Results show that DCs in the draining lymph nodes are activated following infection with L. major. Furthermore, bone marrow-derived DCs as well as DCs freshly isolated from the spleen of C57BL/6 mice can be activated by either heat-killed or live L. major in vitro. In sharp contrast, L. major failed to activate DCs from TLR9(-/-) mice. Noteworthily, activation of DCs was abolished either following treatment of the parasites with DNase or after acidification of the endosomal compartment of DCs by chloroquine, pinpointing the DNA of L. major as the possible ligand of TLR9 leading to the activation of DCs. Results showed that DNA purified from L. major was indeed capable of activating DCs in a strictly TLR9-dependent manner. Moreover we showed that the L. major DNA-induced TLR9 signaling in DCs condition these cells to promote IFN-gamma production by CD4(+) T cells.
在其脊椎动物宿主中，利什曼原虫会接触到表达Toll样受体（TLR）的细胞。在本研究中，我们使用基因抗性的C57BL/6小鼠，这些小鼠分别缺乏TLR2、TLR4或TLR9，结果显示只有缺乏TLR9的小鼠对大型利什曼原虫感染更易感。与野生型C57BL/6小鼠相比，缺乏TLR9的小鼠解决其损伤并控制寄生虫生长的效率要低得多。TLR9的缺失还会短暂抑制治愈性Th1反应的发展。为了分析TLR9基因敲除（-/-）小鼠这种异常反应的可能原因，我们研究了TLR9对大型利什曼原虫激活树突状细胞（DC）的重要性。结果表明，感染大型利什曼原虫后，引流淋巴结中的DC会被激活。此外，来自C57BL/6小鼠骨髓的DC以及从脾脏中新鲜分离的DC在体外可被热灭活或活的大型利什曼原虫激活。与之形成鲜明对比的是，大型利什曼原虫无法激活TLR9基因敲除（-/-）小鼠的DC。值得注意的是，在用脱氧核糖核酸酶处理寄生虫后，或者在用氯喹酸化DC的内体区室后，DC的激活均被消除，这表明大型利什曼原虫的DNA可能是导致DC激活的TLR9配体。结果表明，从大型利什曼原虫中纯化的DNA确实能够以严格依赖TLR9的方式激活DC。此外，我们还表明，大型利什曼原虫DNA在DC中诱导的TLR9信号使这些细胞能够促进CD4(+) T细胞产生γ干扰素。
