Function of mouse lectin receptors

在本研究中，我们旨在阐明小鼠c型凝集素SIGNR3和DCIR1的作用。SIGNR3是小鼠DC-SIGN的同源基因，可识别酵母菌和白色念珠菌。我们建立了新的针对SGINR3的单克隆抗体，并检测了SIGNR3^+细胞的原位分布。它们被证明存在于真皮、皮下淋巴结和循环血液中。真皮和淋巴结有两种类型的SIGNR3^+细胞；一个是CD11c^+树突状细胞，另一个是巨噬细胞。在淋巴结中，它们分布在滤泡间区，靠近皮层和髓质。SIGNR3仅在血液中的CD115^+ Ly6C^<低脂>单核细胞中表达。在炎症反应期间，在引流淋巴结中观察到SIGNR3^+细胞大量增加，特别是在HEV周围。这些结果暗示SIGNR3^+单核细胞被募集到炎症组织的可能性。本研究旨在检验这种可能性。另一方面，通过Western blot和流式细胞术，不仅检测到树突状细胞中存在ITIM的DCIR1的表达，还检测到B细胞、中性粒细胞、单核细胞和巨噬细胞的表达。有趣的是，DCIR1分子在稳定状态下主要存在于细胞质中，在炎症细胞因子和TLR配体的刺激下，其表面表达上调，无需重新合成。此外，募集到炎症部位的粒细胞在细胞表面表达丰富的DCIR1。在DMSO刺激诱导分化为中性粒细胞的HL60细胞中也观察到类似的现象。DCIR1与SIGNR3共享EPN基序，并被发现与zymosan、热杀死和活的白色念珠菌结合。在与特异性抗体交联后，DCIR1被磷酸化并与SHP-1和SHP-2相关。因此，dcir1介导的信号可能参与了炎症反应的调控。

In this study, we aimed to elucidate role of mouse C-type lectins, SIGNR3 and DCIR1. SIGNR3 is a homologue of mouse DC-SIGN and recognizes zymosan and C. albicans. We established new monoclonals antibody specific for SGINR3 and examined the distribution of SIGNR3^+ cells in situ. They were shown to localize in dermis, subcutaneous lymph nodes, and circulating blood. There were two types of SIGNR3^+ cells in the dermis and node ; one was CD11c^+ dendritic cells and the other macrophages. In lymph nodes, they were distributed in interfollicular regions, near HEV in paracortex and medulla. SIGNR3 is expressed only in CD115^+ Ly6C^<int-low> monocytes in the blood. During inflammatory response, a large increase in SIGNR3^+ cells is observed in draining nodes, particularly around HEV. These results imply the possibility that SIGNR3^+ monocytes are recruited into inflamed tissue. This study aimed to examine this possibility.On the other hand, expression of DCIR1, which is characterized by the presence of ITIM in its cytoplasmic portion, was detected not only dendritic cells, but also B cells, neutrophil, monocytes and macrophages by Western blot and flowcytometry. Interestingly, DCIR1 molecules were present mainly in cytoplasm in the steady state and the surface expression was up-regulated by the stimulation with inflammatory cytokines and TLR ligands without de novo synthesis. In addition, granulocytes recruited into inflammatory site expressed abundant DCIR1 on cell surface. Similar phenomenon was also observed in HL60 cells after stimulation with DMSO that induces differentiation to neutrophil. DCIR1 shared EPN motif with SIGNR3 and was found to bind to zymosan, heat-killed and live C. albicans. Upon cross-linking with specific antibody, DCIR1 was phosphorylated and associated with SHP-1 and SHP-2. Therefore, DCIR1-mediated signal may be involved in the regulation of inflammatory response.