TLR-dependent formation of multinucleated giant cells

在分枝杆菌感染中，多核巨细胞（MGCs）是由巨噬细胞在严格调控的过程中产生的，这一过程仅限于多细胞肉芽肿。在前三年的资助中，我们已经描述了toll样受体2激活通过诱导复制应激和DNA损伤反应来指导多倍体MGC，从而导致修饰的细胞分裂和有丝分裂缺陷。在这个过程中一个重要的中间体是一氧化氮，它会导致DNA损伤并损害p53的功能。因此，分枝杆菌似乎矛盾地从抗菌努力中获利，通过驱动转化为允许的MGCs。在接下来的三年里，我们的目标是进一步确定MGC形成的分化机制，因为它们形成了合理的治疗靶点。我们的中心假设是，共同单核细胞祖细胞（cops）是专用的MGC前体。伴随骨髓输出和募集到感染部位，cmps获得了一种新的表型，表达典型的单核细胞表面标记，但保留了增殖能力和MGC前体潜能。此外，我们认为髓系转录因子IRF8对MGC的抗菌功能至关重要。具体目的是：a)确定源自cmps的MGC形成和功能的转录程序；b)确定IRF8在组织巨噬细胞发育中的定性作用；c)分析MGC中的免疫代谢。在缺乏IRF8作为分枝杆菌感染的模型免疫缺陷的情况下，破译MGC形成的细胞和转录先决条件有望揭示增强抗分枝杆菌免疫的新策略。

In mycobacterial infections multinucleated giant cells (MGCs) arise from macrophages in a tightly regulated process, which is confined, to multicellular granulomas. In the first three years of funding we have delineated that Toll-like receptor 2 activation instructs polyploid MGC via induction of replication stress and a DNA damage response leading to modified cell divisions and mitotic defects. An important intermediate in this process is nitric oxide, which causes DNA damage and impairs p53 function. Thus mycobacteria appear to paradoxically profit from antimicrobial efforts by driving transformation into permissive MGCs. In the upcoming three years we aim at further defining differentiation mechanisms underlying MGC formation, since they form rational therapeutic targets. Our central hypothesis is that common monocyte progenitors (cMoPs) are dedicated MGC precursors. Concomitant to bone-marrow egress and recruitment to the site of infection, cMoPs acquire a novel phenotype with expression of typical monocyte surface markers, yet preservation of proliferative capacity and MGC precursor potential. Moreover, we propose that the myeloid transcription factor IRF8 is essential for full antimicrobial MGC function. The specific aims are a) to define the transcriptional program in the formation and function of MGC originating from cMoPs, b) to define the qualitative role of IRF8 in the development of tissue macrophages, and c) to analyze immunometabolism in MGC. Deciphering the cellular and transcriptional preconditions for MGC formation, with lack of IRF8 as a model immunodeficiency for mycobacterial infections, is expected to reveal novel strategies to boost antimycobacterial immunity.