Characterization of BATF functions in plasmacytoid dendritic cell development and type I interferon production in antiviral immune responses

浆细胞样树突状细胞（pDC）具有产生大量I型干扰素（IFN）的能力。因此，pDC在介导保护性免疫应答或引起免疫病理学的病毒感染中发挥重要且复杂的作用。此外，pDC的失调激活与自身免疫性疾病相关。pDC介导的免疫调节的细胞和分子机制知之甚少。为了鉴定pDC功能的新型调节剂，我们发现了Batf（碱性亮氨酸拉链转录因子，ATF样）在产生IFN β的pDC中的高表达。BATF与BATF 2和BATF 3一起构成AP-1转录因子大家族的一个亚家族。已知其负调控AP-1介导的基因转录，但也通过与其他转录因子如IRF家族成员相互作用而发挥正转录活性。BATF在T辅助细胞（Th）类型的分化和细胞因子产生中以及在B细胞中的类别转换重组中是必需的。到目前为止，还不知道BATF在pDC发育或功能中的意义。（i）BATF在产生I型IFN的pDC中高度表达，（ii）在Flt 3-L培养物中以及在来自Batf缺陷（Batf-/-）小鼠的次级淋巴器官中Toll样受体（TLR）9活化后，pDC的频率增加，（iii）Batf-/-pDC上DC标志物CD 11 c的表面表达水平降低，（iv）Batf-/-pDC响应于TLR 9体外活化产生的I型IFN的量增加，并且存在于淋巴细胞性脉络丛脑膜炎病毒（LCMV）感染的Batf-/-小鼠的血清中，和（v）分别与Batf+/+同窝对照相比，在Batf-/-pDC存在下的体外病毒感染率降低。此外，（vi）在Batf-/-与Batf+/+ pDCs的初步转录组分析中，I型IFN特征和DC分化基因表达的差异是可见的。我们设想的双轨工作计划涵盖分子和细胞方面：在第一轨道中，我们将定义BATF介导的pDC中I型IFN产生调节的分子机制，并在活化后对Batf-/- vs. Batf+/+ pDC中的转录和表观遗传时间模式进行全基因组分析，并鉴定活化复合物内的BATF相互作用伴侣。第二部分利用pDC特异性BATF缺陷小鼠和竞争性骨髓嵌合体研究BATF在pDC发育和分化中的作用，并描述LCMV感染中pDC特异性BATF的功能。详细分析BATF在pDC中的功能和调控途径，将为感染性疾病和干扰素病中控制BATF功能提供关键信息。

Plasmacytoid dendritic cells (pDCs) harbor the capacity to produce high amounts of type I interferons (IFNs). Thereby, pDCs play an important and complex role in viral infections mediating protective immune responses or causing immunopathology. Also, dysregulated activation of pDCs is associated with autoimmune diseases. The cellular and molecular mechanisms of pDC mediated immune regulation are poorly understood. In aiming to identify novel regulators of pDC functions we discovered a high expression of Batf (Basic leucine zipper transcription factor, ATF-like) in IFN beta-producing pDCs. BATF together with BATF2 and BATF3 comprise a subfamily of the larger group of AP-1 transcription factors. It is known to negatively regulate AP-1 mediated gene transcription, but also to exert positive transcriptional activities by interacting with other transcription factors such as IRF family members. BATF has been shown to be essential in the differentiation and cytokine production of T helper (Th) cell types and in class switch recombination in B cells. No implications for BATF in pDC development or function are known so far.In preliminary studies we made the following observations: (i) BATF is highly expressed in type I IFN producing pDCs, (ii) frequencies of pDCs are increased in Flt3-L cultures and after Toll like receptor (TLR) 9 activation in secondary lymphoid organs from Batf-deficient (Batf-/-) mice, (iii) surface expression levels of the DC marker CD11c are reduced on Batf-/- pDCs, (iv) increased amounts of type I IFN are produced by Batf-/- pDCs in response to TLR9 activation in vitro and present in the serum of lymphocytic choriomeningitis virus (LCMV) infected Batf-/- mice, and (v) viral infection rates in vitro in the presence of Batf-/- pDCs are reduced, as compared to Batf+/+ littermate controls, respectively. Also, (vi) a type I IFN signature and differences in the expression of DC differentiation genes are visible in preliminary transcriptome profiling of Batf-/- vs. Batf+/+ pDCs.The proposed study will define the mechanisms of BATF-mediated functions in pDC development and effector functions in anti-viral immunity. Our envisaged twin-track work programme covers molecular and cellular aspects: In the first track we will define the molecular mechanisms of BATF-mediated regulation of type I IFN production in pDCs and perform genome wide profiling of transcriptional and epigenetic temporal patterns in Batf-/- vs. Batf+/+ pDCs after activation and identify BATF-interaction partners within the activating complex. The second track investigates the role of BATF in pDC development and differentiation using pDC specific BATF-deficient mice and competitive bone marrow chimeras and characterizes pDC specific BATF functions in LCMV infection.Detailed analyses of the functions and pathways regulated by BATF in pDCs will provide critical information for controlled manipulation of BATF functions in infectious diseases and interferonopathies.