Role of PD-1/PD ligand system in the pathogenesis of rheumatoid arthritis

本研究的目的是澄清(1)我们首次描述的抑制共刺激系统PD-1/PD-L配体（PD-L1）是否存在于类风湿关节炎（RA）中，(2)如果存在，PD-1/PD-L系统的异常是否导致RA的诱导。以下是我们取得的成就：RA患者的滑液（SF）中含有PD-1+CD4+T细胞，而在骨关节炎患者的外周血或SF中基本未检测到此类细胞。这些细胞也表达CTLA-4，且细胞内IL-10呈阳性，因此被认为具有抑制功能。干扰素(IFN)- γ在体外培养的滑膜细胞上强烈诱导细胞表面PD-L1的表达，而其他共刺激分子如B7.1和B7.2则没有。应用新制备的单克隆抗体免疫组织化学方法检测RA患者关节组织中PD-1和PD-L1的表达。PD-L1在滑膜组织表层细胞和内皮细胞上强烈表达。PD-L1也在大部分表达PD-L1的浸润细胞上表达。目前正在用冷冻样品的双染色法研究哪种细胞表达pp - 1，这些细胞产生哪些细胞因子。胶原诱导关节炎（CIA）小鼠滑膜细胞PD-L1阳性，部分骨髓细胞PD-L2阳性。给CIA小鼠抗PD-L1抗体倾向于抑制关节炎的发生。已知PD-1敲除（KO）小鼠自然发生关节炎，由于缺乏PD-1系统，这些小鼠的CIA很可能比野生型小鼠的CIA更严重，这再次表明PD-1/PD-L1系统参与了RA的病因学。使KO小鼠无特定病原体的过程目前正在进行中。

The aim of the investigation is to clarify whether (1) the abnormalities of the inhibitory co-stimulatory system PD-1/PD-L ligand (PD-L1), which we first described, exist in rheumatoid arthritis (RA) and (2) if so, the abnormalities of PD-1/PD-L system result in the induction of RA. The followings are our achievements ;1. Synovial fluid (SF) from RA patients contained PD-1+CD4+T cells, while such cells were essentially not detected in peripheral blood or SF from osteoarthritis patients. These cells were considered to have the inhibitory function since they also expressed CTLA-4 and were positive for the intracelluar IL-10. Interferon (IFN)-gamma strongly induced the cell-surface expression of PD-L1, but not the other co-stimulatory molecules such as B7.1 and B7.2, on cultivated synovial cells in vitro.2. The expression of PD-1 and PD-L1 in articular tissue of RA patients was examined immunohistochemically using the newly developed monoclonal antibodies. PD-L1 was strongly expressed on the surface layer cells of synovial tissue and the endothelial cells. PD-L1 was also expressed on the majority of infiltrated cells expressed PD-L1. It is currently under examination by the double staining method on frozen samples what kind of cells express PP-I and which cytokines these cells produce.3. On collagen induced arthritis (CIA) mice, synovial cells were positive for PD-L1 while some of the bone marrow cells were PD-L2 positive. Administration of anti PD-L1 antibodies to the CIA mice tended to inhibit the onset of arthritis.4. PD-1 knockout (KO) mice are known to develop arthritis naturally, and it is highly, possible that CIA on these mice is severer than CIA on wild type mice due to the lack of PD-1 system, which again indicate the involvement of PD-1/PD-L1 system on the etiology of RA. The process to make the KO mice specific pathogen free is currently on-going.