慢性乙型肝炎患者外周血树突状细胞PD-L1表达的相关研究

目的：探讨慢性乙型肝炎（CHB）患者外周血树突状细胞（DCs）的PD—L1表达水平，及其对DCs刺激T细胞增殖的影响。方法：采集22例慢性HBeAg阳性CHB患者、8例急性恢复期乙型肝炎（AHB）患者和10例健康人（NC）的外周血，分离单个核细胞（PBMC）并诱导DCs的增殖和活化。相对荧光定量PCR测定DCs的PD—L1、PD—L2分子mRNA水平，流式细胞术测定DCs表面PD—L1和PD—L2的表达率。同时，测定外周血DCs刺激同种异体反应性T细胞增殖的能力，及抗PD—L1单抗对CHB组DCs刺激功能的影响。结果：体外成功诱导了外周血DCs的增殖和成熟。与NC组相比较，CHB组和AHB组患者外周血DCs内PD—L1的mRNA水平均显著增高（P均〈0．05），但CHB组和AHB组间差异无统计学意义。CHB组患者外周血DCs表面PD—L1表达率较AHB组、NC组均有明显增高（P均〈0．01）。而外周血DCs的PD—L2 mRNA水平及PD—L2在DCs表面的表达率在各实验组之间无明显差异（P均〉0．05）。CHB组外周血DCs刺激T细胞增殖的功能较AHB组和NC组明显降低（P均〈0．01），抗PDL1抗体能显著增强CHB患者DCs刺激T细胞反应的能力。CHB患者外周血DCs表面PD—L1表达率与血清HBV病毒载量成正相关（r=0．34，P=0．007）。结论：外周血DCs表面PDL1表达水平在慢性HBeAg阳性乙肝患者明显升高，抗PD—L1抗体可有效增强CHB患者外周血DCs刺激T细胞增殖反应的能力，表明PD—L1的高表达可能与T细胞免疫反应低下和HBV病毒高复制密切相关。

PD-L1 expression in circulating dendritic cells of patients with chronic hepatitis B

OBJECTIVE: To determine the PD-L1 expression levels in circulating dendritic cells(DCs) of patients with HBeAg positive chronic hepatitis B, and to investigate the effects of anti-PD-L1 antibody on DCs stimulating capacity of allogeneic lymphocytes. METHODS: DCs were separated and induced from 22 HBeAg positive chronic hepatitis B patients (CHB), 8 acute resolved hepatitis B patients (AHB) and 10 healthy blood donors. PD-L1 and PD-L2 expression in DCs were determined using real-time RT-PCR and flow cytometry. The potential of circulating DCs on the proliferation of allogeneic T cells was detected and a specific monoclonal antibody against PD-L1 was used in alternative experiments. Serum HBV-DNA titers were measured using real-time PCR, and HBV markers and liver function were also evaluated. RESULT: The expression of PD-L1 but not PD-L2 was upregulated in circulating DCs of CHB patients, compared to AHB patients and healthy controls (both P<0.01). CHB patients with greater than 106 copies /ml of serum HBV DNA loads had a higher level of PD-L1 in circulating DCs than those with less than 106 copies/ml (P<0.05), and the high expression of PD-L1 in DCs was positively correlated with the plasma viral load. Moreover, the potential of circulating DCs from CHB patients was significantly decreased compared with healthy controls or AHB patients, while the blockade of PD-L1 using anti-PD-L1 monoclonal antibody increased the ability of DCs on the proliferation of allogeneic T cells in vitro. Conclusion: High expression of PD-L1 on circulating DCs may be associated with T cell exhaustion and persistent high levels of HBV DNA replication in chronic hepatitis B patients.