Functional analysis of a novel inhibitory receptor expressed on plasmacytoid dendritic cells

抑制性受体通过对细胞功能的负性调节，在免疫反应的精细调控和终止中起着至关重要的作用。已经在不同类型的细胞上发现了许多抑制性受体。特别是，自然杀伤细胞上的抑制性受体已经得到了很好的表征。抑制性NK受体对靶细胞表面MHC-I类或相关分子的识别使NK细胞既能阻止自身杀伤，又能破坏MHC-I类分子水平降低的不适当细胞。Ly49Q是一种携带ITIM的抑制性受体，属于Ly49家族，是NK受体的一个亚家族。虽然Ly49Q与Ly49家族有很高的结构相似性和染色体定位，但Ly49Q具有不同于Ly49家族其他成员的独特功能。Ly49Q在NK和NKT细胞上不表达，但主要在巨噬细胞和浆细胞树突状细胞上表达。Ly49Q拥有英博…更多的与SHP-1和SHP-2以酪氨酸磷酸化依赖的方式联系在一起。我们在这里证明了不同的Ly49Q表达水平定义了骨髓中PDCs的顺序成熟阶段。此外，根据Ly49Q的表达，我们鉴定了不同功能的PDCs亚群。大多数CD11c~+B220~+PDCs在脾和淋巴结中高表达Ly49Q。然而，骨髓、血液、肝脏和肺中的PDCs中有相当一部分缺乏Ly49Q的表达。Ly49Q^-PDCs产生干扰素-αβ/、IL-6和IL-12p70的能力低于Ly49Q^+PDCs。然而，有趣的是，Ly49Q^-PDCs在CpG和HvJ作用下产生的肿瘤坏死因子-α水平与Ly49Q^+PDCs相当。因此，Ly49Q是揭示PDCs成熟过程和区分不同功能亚群的有用标记。我们的结果表明，PDCs的细胞因子谱在其成熟过程中会发生变化，并且PDCs在不同的成熟阶段发挥不同的免疫功能。为了了解Ly49Q的功能相关性以及巨噬细胞和树突状细胞对MHC I类分子的识别，我们开始建立表达Ly49Q的转基因小鼠。较少

Inhibitory receptors play crucial roles for fine regulation and termination of immune responses by negatively regulating cellular functions. A number of inhibitory receptors have been identified on various types of cells. In particular, inhibitory receptors on natural killer cells have been well characterized. It has been postulated that recognition of MHC class I, or related molecules, on target cells by inhibitory NK receptors allows NK cells to prevent self killing but destroy inappropriate cells possessing decreased levels of MHC class I.Ly49Q is an ITIM-bearing inhibitory receptor belonging to Ly49 family that is known as one of subfamilies of NK receptors. Even though Ly49Q is classified into Ly49 family because of highly structural similarities and of its chromosomal location, Ly49Q has unique features different from other Ly49 family members. Ly49Q is not expressed on NK and NKT cells, but predominantly expressed on macrophages and plasmacytodi dendritic cells. Ly49Q has an abi … More lity to associate with both SHP-1 and SHP-2 in a tyrosine phosphorylation-dependent manner.We here demonstrate that different expression levels of Ly49Q defined sequential maturational stages of PDCs in bone marrow. Moreover, we identified functionally different subsets of PDCs according to the expression of Ly49Q. Most CD11c^+B220^+PDCs in spleen and lymph node expressed high levels of Ly49Q. However, a significant portion of PDCs in BM, blood, liver and lung lacked Ly49Q expression. Ly49Q^- PDCs possessed lower abilities to produced IFN-αβ/, IL-6 and IL-12 p70 than Ly49Q^+ PDCs in response to TLR ligands. Interestingly, however, Ly49Q^- PDCs bore an ability to produce equivalent levels of TNF-α to Ly49Q^+ PDCs when exposed to CpG and HVJ. Thus, Ly49Q is a useful marker to reveal maturation process of PDCs and to distinguish functionally different subsets of PDCs. Our results suggest that cytokine profiles of PDCs alter during their maturational processes and that PDCs play different immunological functions depending on their maturational stages. To understand functional relevance of Ly49Q as well as MHC class I recognition by macrophages and dendritic cells, we started to establish transgenic mice expressing Ly49Q. Less