Identification of mechanisms for the tolerogenic predisposition of human thymic and tumor dendritic cells

树突状细胞（DC）是免疫系统的关键调节因子。为了获得更多关于人原代DC的知识，我们最近进行了转录组和表面活性组分析。我们可以证明从淋巴造血系统中分离的DC亚群显示出很强的个体发生关系。有趣的是，我们进一步发现非淋巴组织中的微环境对整体DC转录组表现出更强的影响。由于我们以前的结果是从稳态获得的，我们现在已经开始研究炎症条件下的DC亚群。我们的初步数据表明，尽管从血液、胸腺和脾组织中分离的DC亚群具有相似的DC亚群特异性TLR表达谱，但胸腺DC亚群在刺激后其细胞因子分泌减少。这与血液和脾脏DC相反，血液和脾脏DC显示出完整的活化谱，包括共刺激分子和促炎细胞/趋化因子（如IL-12和RANTES）的表达。这种缺失的胸腺DC的细胞因子和趋化因子分泌伴随着完全阻断CD 4 + T细胞极化为TH 1细胞。由于这种行为是在DC分离和体外刺激后观察到的，因此我们在此假设这种效应可能来自胸腺环境导致的强致耐受性印迹。胸腺DC的半成熟表型可能与肿瘤DC的表型相似。因此，我们进一步假设，肿瘤微环境诱导类似的表观遗传和/或转录组的变化，浸润肿瘤DC相比，在胸腺中定位的DC。为了检验我们的假设，我们在此希望i）确定人血液和胸腺DC之间的功能差异，ii）评估人胸腺和肿瘤DC亚群之间的相似性和差异，以及iii）分析实验小鼠系统中胸腺和肿瘤DC亚群的致耐受性倾向的机制。因此，为了研究从胸腺、血液和肿瘤中分离的分选的DC亚群在TLR配体刺激后的转录变化，我们将进行RNAseq分析，而这些细胞的表观遗传状态将通过ChIPseq分析来确定。此外，我们将从功能上分析候选调节机制，例如细胞内信号通路和转录因子激活的差异。DC和T细胞应答的测量将包括多色流式细胞术、CBA和PhosFlow测定。我们期望鉴定参与胸腺和肿瘤DC亚群的致耐受性易感性的关键参与者，允许开发和测试干预策略，例如促进肿瘤治疗。

Dendritic cells (DCs) are key regulators of the immune system. To gain more knowledge on human primary DCs, we recently performed transcriptome and surfactome analyses . We could demonstrate that DC subsets isolated from the lymphohematopoietic system displayed a strong ontogenetic relationship. Interestingly, we further found that the microenvironment in non-lymphoid tissues exhibited a stronger influence on the overall DC transcriptome. As our previous results were obtained from the steady-state, we have now started to investigate the DC subpopulations under inflammatory conditions. Our preliminary data demonstrate that, although the DC subsets isolated from blood, thymic, and splenic tissues have a similar DC subset specific TLR expression profile, thymic DC subsets were diminished in their cytokine secretion upon stimulation. This was in contrast to blood and splenic DCs, which displayed the full activation spectrum, including the expression of costimulatory molecules and pro-inflammatory cyto-/chemokines, such as IL-12 and RANTES. This missing cyto- and chemokine secretion of thymic DCs was accompanied by a complete block of CD4+ T cell polarization into TH1 cells. As this behavior was observed after the isolation of the DCs and their stimulation in vitro, we here hypothesize that this effect might derive from a strong tolerogenic imprinting as consequence of the thymus environment. The observed semi-mature phenotype of thymic DCs might resemble the phenotype of tumor DCs. Therefore, we further hypothesize that the tumor microenvironment induces similar epigenetic and/or transcriptomic changes in infiltrating tumor DCs compared to DCs localized in the thymus. In order to test our hypotheses, we here want to i) determine functional differences between human blood and thymic DCs, ii) evaluate similarities and differences between human thymic and tumor DC subsets, and iii) analyze the mechanisms for tolerogenic predisposition of thymic and tumor DC subsets in experimental murine systems. Thus, to investigate transcriptional changes upon TLR ligand stimulation of sorted DC subpopulations isolated from thymi, blood, and tumors, we will perform RNAseq analyses, while the epigenetic status of these cells will be determined by ChIPseq analyses. Furthermore, we will functionally analyze candidate regulatory mechanisms, such as differences in intracellular signaling pathways and transcription factor activation. The measurement of DC and T cell responses will include multi-color flow cytometry, CBA, and PhosFlow assays. We expect that the identification of the key players involved in the tolerogenic predisposition of thymic and tumor DC subsets, allows for the development and testing of intervention strategies, e.g. to promote tumor therapies.