Dissecting pathogen persistence- versus clearance-promoting functions of monocyte-derived cell populations during L. major infection

组织损伤和感染导致免疫细胞从血流中大量募集。在这些募集的细胞中，单核细胞产生多功能的吞噬细胞系统，其可以吸收和中和病原体，激活适应性免疫系统，但也诱导组织修复。尽管在各种疾病模型中进行了深入研究，但仍不清楚特定单核细胞亚群的不同功能在募集到组织后是如何诱导的，以及这些功能如何有助于控制感染。这一问题对于胞内病原体如L.主要，单核细胞来源的细胞可以作为病原体细胞内生长的小生境，也可以作为对抗感染的效应细胞。主要具有不同的细胞内增殖速率，表现出特征性的基因表达模式，并被效应T细胞差异性地接合。这种差异如何与单个单核细胞衍生的亚群的不同作用有关，即在多大程度上它们促进病原体的细胞内存活和持续存在，或通过激活免疫系统清除病原体，尚不清楚。严重的皮肤感染为了实现这一目标，我们将采用荧光报告系统，使我们能够在体内追踪单核细胞在感染部位的募集和激活。(2)不同的亚群如何与T细胞相互作用并调节T细胞效应功能？为此，我们将通过活体2-光子显微镜在体内，并通过活细胞成像和RNA测序离体，不同的单核细胞衍生的细胞亚群的相互作用和激活效应T细胞的能力进行调查。(3)在不同的单核细胞衍生细胞亚群中特异性表达的候选基因如何影响这些亚群在促进病原体持久性与清除方面的作用？为了研究这个问题，我们将应用混合骨髓嵌合模型结合部分细胞耗竭，以解决候选基因缺陷对病理和感染course.The拟议的研究应关键有助于我们理解的机制和动力学的不同单核细胞衍生的细胞亚群如何影响感染过程中的细胞内在与细胞外在的影响。鉴于单核细胞广泛参与各种感染性、炎性和恶性疾病，阐明控制这种免疫刺激与免疫调节功能的机制可以指导特异性靶向单核细胞中这种平衡的新治疗策略。

Tissue damage and infection results in the massive recruitment of immune cells from the bloodstream. Among these recruited cells, the monocytes give rise to a versatile system of phagocytes which can take up and neutralize pathogens, activate the adaptive immune system, but also induce tissue repair. Despite intense investigation in a variety of disease models, it has remained unclear how the different functions of specific monocyte subsets are induced after recruitment to the tissue, and how these functions contribute to the control of infections. This question is especially important for the infection with intracellular pathogens such as L. major, for which monocyte-derived cells can serve both as niches for intracellular growth of the pathogen, but also as effector cells fighting the infection.In our previous work, we have identified distinct subsets of monocyte-derived cells that harbour L. major with different intracellular proliferation rates, exhibit characteristic gene expression patterns, and are differentially engaged by effector T cells. How such differences relate to distinct effects of the individual monocyte-derived subsets, i.e. to what extent they promote intracellular survival and persistence of the pathogen, or pathogen clearance by activating the immune system, is unclear yet.The objective of the proposed research is therefore to investigate the following questions:(1) How are the monocyte-derived cell subsets are recruited to, and activated at, the site of L. major skin infection? To achieve this, we will employ fluorescent reporter systems that allow us to track in vivo the recruitment and activation of monocytes to the site of infection.(2) How do the different subsets interact with T cells and modulate T cell effector functions? For this, we will investigate by intravital 2-photon microscopy in vivo, and by live cell imaging and RNA sequencing ex vivo, the capacity of different monocyte-derived cell subsets to interact with and activate effector T cells.(3) How do candidate genes shown to be specifically expressed in distinct monocyte-derived cell subsets impact on the role of these subsets in promoting pathogen persistence versus clearance? To investigate this question, we will apply mixed bone marrow chimeric models combined with partial cell depletion to address cell-intrinsic versus cell extrinsic effects of candidate gene deficiencies on pathology and infection course.The proposed research should critically contribute to our understanding of the mechanisms and dynamics of how different monocyte-derived cell subsets impact on the course of infection. Given the widespread involvement of monocytes in a variety of infectious, inflammatory and malignant diseases, elucidating the mechanisms that control such immunostimulatory versus immunomodulatory functions could guide novel therapeutic strategies targeting this balance specifically in monocytes.