Molecular signaling in the regulation of dendritic cell function

* 树突状细胞（DC）是免疫反应协调的关键参与者。树突状细胞的成熟状态对T细胞功能有着深远的影响。已知成熟DC（mDC）诱导有效的T细胞应答，而未成熟DC（iDC）和半成熟DC（smDC）促进和维持T细胞耐受性。驱动DC发挥免疫原性或调节功能的分子机制尚不完全清楚。我们用低剂量的GM-CSF或GM-CSF+IL-4从NOD和Balb/c小鼠的骨髓中产生DC。我们发现用GM-CSF产生的DC具有半成熟表型，产生大量的IL-10但较少的IL-12，并且具有降低的活化CD 8 + T细胞的能力。用GM-CSF+IL-4产生的LPS活化的DC完全成熟，产生大量的IL-12但较少的IL-10，并诱导CD 8 + T细胞的强烈增殖。Western blot分析显示smDCs中MAP激酶ERK 1/2持续激活，但mDCs中没有。我们还发现ERK 1/2激活参与IL-10的产生而不影响DC表型。NF-？B组分p52、p65和RelB显示p52/p65在smDC中优先活化，而p52/RelB在mDC中优先活化。这些结果表明，RelB在NF？B复合物和ERK 1/2的激活参与了成熟抵抗DC的发育及其增加的IL-10产生。对CREB、AP 1和C/EBP结合能力的分析表明，C/EBP同工型在smDC中被激活，但在mDC中没有。这些结果表明，Rel/B和C/EBP在DCs成熟阶段的控制中起关键作用。已知C/EBP 3转录因子参与巨噬细胞的分化和活化。例如，来自C/EBP 3-KO小鼠的巨噬细胞产生较少的IL-12，并且不能诱导Th 1应答。此外，我们的初步数据支持这样的观点，即在smDC中被激活的C/EBP 3亚型在调节性smDC的产生中起关键作用。假设C/EBP 3转录因子同种型及其调节物触发前体DC（pDC）选择性分化为调节性smDC或效应mDC。目的：*1）分析C/EBP 3在smDC或mDC产生中的相对作用。*2）鉴定触发pDC分化为smDC和mDC的C/EBP 3同种型配偶体。*3）研究C/EB β 1受体或/和β 2受体 * 的激活剂同种型或其抑制剂同种型LIP是否调节smDC和mDC的表型和功能。* 重要性：了解控制DC分化为调节性smDC或效应性mDC的机制将提高我们对基础免疫学的认识，并可能有助于设计用于治疗自身免疫性疾病和病毒感染的新靶向疗法。**

***Dendritic cells (DCs) are key players in the orchestration of the immune response. DCs maturation status has a profound effect on T cell functions. Mature DCs (mDCs) are known to induce an effective T cell response whereas immature (iDCs) and semimature DCs (smDCs) promote and maintain T cell tolerance. The molecular mechanisms that drive DCs to immunogenic or to regulatory functions are not fully known. We have generated DCs from bone marrow of NOD and Balb/c mice either with low doses of GM-CSF or with GM-CSF+IL-4. We found that DCs generated with GM-CSF had a semimature phenotype, produced high amounts of IL-10 but less IL-12, and had a decrease capacity to activated CD8+ T cells. LPS-activated DCs generated with GM-CSF+IL-4 were fully mature, produced large amounts of IL-12 but less IL-10 and induce strong proliferation of CD8+ T cells. Western blot analysis revealed a sustained activation of MAP kinase ERK 1/2 in smDCs but not in mDCs. We also found that ERK1/2 activation is involved in IL-10 production without affecting DCs phenotype. The analysis of NF-?B components p52, p65 and RelB, showed that p52/p65 is preferentially activated in smDCs whereas p52/RelB is preferentially activated in mDCs. These results suggest that the absence of RelB in NF?B complex and that the activation of ERK1/2 are involved in the development of maturation-resistant DCs and their increased IL-10 production. The analysis of the binding capacity of CREB, AP1 and C/EBP which are known for their contribution to increase the expression of costimulatory molecules, and their interaction with NF-kB component, revealed that C/EBPß isoform is activated in smDCs but not in mDCs. These results suggest that Rel/B and C/EBPß played a key role in the control of maturation stage of DCs.***Rational The C/EBPß transcription factors are known to be involved in differentiation and activation of macrophages. For example, macrophages from C/EBPß-KO mice produced less IL-12 and could not induce a Th1 response. Furthermore, our preliminary data support the notion that C/EBPß isoforms, which were activated in smDC, played a critical role in the generation of regulatory smDCs.***Hypothesis C/EBPß transcription factor isoforms and their regulators trigger the selective differentiation of precursor DCs (pDCs) into regulatory smDC or effector mDCs.***Objectives:***1) to dissect relative role of C/EBPß in the generation of smDcs or mDCs. ***2) to identify C/EBPß isoforms partners that trigger differentiation of pDCs into smDC and mDCs. ***3) to investigate whether the activator isoforms of C/EBPß LAP or/and LAP* or its inhibitor isoform LIP regulate smDCs and mDCs phenotypes and functions. ***Significance: Understanding the mechanisms that control differentiation of DCs into regulatory smDCs or effector mDCs will improve our knowledge of basic immunology and may help to design new targeted therapeutics for the treatment of autoimmune diseases and viral infections. **