LEISHMANIA MAJOR INFECTED MACROPHAGE ACTIVATION OF NAIVE T CELLS

实验感染小鼠的原生动物寄生虫，利什曼原虫重大，已被证明是一个非常有用的工具，研究免疫反应机制。最值得注意的是，该模型已经证明了辅助性T细胞亚群的功能二分法也存在于对病原性感染的人类免疫应答中。T细胞介导的免疫应答由抗原呈递细胞（APC）启动，其将源自细胞内病原体的抗原展示在表面MHC分子上。巨噬细胞长期以来被认为是重要的MHC II类APC，但被真实的病原体感染的巨噬细胞的抗原呈递仍在很大程度上未被表征。利什曼原虫模型为探索巨噬细胞在激活T辅助细胞中的作用提供了相当大的潜力，因为利什曼原虫寄生虫仅在宿主巨噬细胞内复制，并引起直接和明确的MHC II类限制性反应。本文提出的实验使用独特的抗原呈递系统来探索T细胞对感染的巨噬细胞应答的启动的三个阶段。首先，将确定MHC II类分子结合利什曼原虫抗原的细胞内区室。实验将解决这个隔间是否与利什曼原虫寄生的寄生虫空泡相同。其次，将表征利什曼原虫感染的巨噬细胞的共刺激能力。将测定B7和CD 40分子的组成性和诱导性表达，并测试其在T细胞活化中的作用。这些实验可以揭示细胞内利什曼原虫或T细胞参与对感染的巨噬细胞的共刺激能力的影响。最后，将研究感染的巨噬细胞对IL-12的转录。IL-12对于应答T细胞分化为Th 1细胞是必需的，Th 1细胞是控制L.严重感染巨噬细胞是IL-12最可能的来源，但利什曼原虫可能干扰IL-12的诱导。将在巨噬细胞分化的两个阶段，即感染后立即和IFN γ和TNF α激活后，测试通过CD 40的T细胞依赖性IL-12诱导。这些研究将证明巨噬细胞分化响应感染和抗原特异性T细胞接合的独特模式。技术将建立进一步探索细胞内病原体，巨噬细胞APC和响应T细胞之间的分子串扰。

Experimental infection of mice with the protozoan parasite, Leishmania major, has proven to be an extremely useful tool for investigating immune response mechanisms. Most notably, this model has demonstrated the functional dichotomy of T helper cell subsets also present in human immune responses to pathogenic infections. T cell-mediated immune responses are initiated by antigen presenting cells (APCs), which display antigens derived from intracellular pathogens on surface MHC molecules. Macrophages have long recognized as important MHC class II APCs, but antigen presentation by macrophages infected with real pathogens is still largely uncharacterized. The Leishmania model provides considerable potential for exploring the role of macrophages in activating T helper cells, because Leishmania parasites replicate exclusively within host macrophages and elicit a direct and well-defined MHC class II-restricted response. The experiments proposed here use a unique antigen presentation system to explore three stages in the initiation of a T cell response to infected macrophages. First, the intracellular compartment where MHC class II molecules bind Leishmania antigens will be defined. Experiments will address whether this compartment is identical to the parasitophorous vacuole where Leishmania parasites reside. Second, the co-stimulatory capacity of Leishmania-infected macrophages will be characterized. The constitutive and induced expression of B7 and CD40 molecules will be determined and their role in T cell activation will be tested. These experiments may reveal an effect of intracellular Leishmania or T cell engagement upon the co-stimulatory capacity of the infected macrophage. Finally, the transcription of IL-12 by infected macrophages will be investigated. IL-12 is necessary for the differentiation of responding T cells into Th1 cells, the appropriate subset for controlling L. major infection. Macrophages are the most likely source of IL-12 but Leishmania may interfere with IL-12 induction. T cell dependent IL-12 induction via CD40 will be tested at two stages of macrophage differentiation, immediately after infection and following activation by IFNgamma and TNFalpha. These studies will demonstrate a distinct pattern of macrophage differentiation in response to infection and antigen-specific T cell engagement. Techniques will be established for further exploration of the molecular crosstalk between intracellular pathogens, macrophage APCs, and responding T cells.