Department of Endocrinology, The Second Affiliated Hospital of Soochow University, Suzhou, China.
Clinical Medicine Research Center, Affiliated Hospital 2 of Nantong University, Nantong, China.
Acta Diabetol. 2021 Sep;58(9):1239-1249. doi: 10.1007/s00592-021-01711-z. Epub 2021 Apr 23.
Chronic inflammation of autoimmune diseases, including type 1 diabetes (T1D), is mainly mediated by memory T(Tm) cells, predominantly effector memory T (Tem) cells. The roles of the programmed death-1 (PD-1) receptor on lymphocytes have been well studied in tumor and other infection models. However, little is known about the relationship between the expression of PD-1 on CD8 Tem cells and the pathogenesis of T1D.
A total of 52 patients diagnosed with T1D and 39 gender-, age-, and ethnically matched health control individuals were enrolled in this study. Peripheral blood mononuclear cells from these individuals were isolated and analyzed by flow cytometry. We evaluated the frequencies of PD-1 CD8 memory T cell subsets from patients' peripheral blood with T1D and the spleen cells of nonobese diabetic (NOD) mice in the present study. We also investigated the effects of blocking PD-1/PD-L1 pathway on islet's inflammation in NOD mice.
Frequencies of PD-1 CD8 Tem cells were decreased significantly in PBMC of patients with T1D (40.73 ± 12.72 vs 47.43 ± 15.56, *p < 0.05). The frequencies of PD-1 CD8 Tem cells were decreased in patients with T1D who were positive for two or more autoantibodies compared with the patients with one autoantibody (13.46% vs 46.95 ± 12.72%, *p < 0.05). Meanwhile, the frequencies of PD-1 CD8 central memory T (Tcm) cells were also significantly decreased in patients with two or more autoantibodies compared with other groups (≥ 2AAb vs HC 33.1 ± 8.92% vs 43.71 ± 11.78%, *p < 0.05; ≥ 2AAb vs AAb-33.1 ± 8.92% vs 41.65 ± 11.2%, *p < 0.05; ≥ 2AAb vs 1AAb 33.1 ± 8.92% vs 48.09 ± 10.58%, ***p < 0.001). The frequencies of PD-1CD8 Tem cells were positively correlated with fasting serum C-peptide levels (r = 0.4308, *p < 0.05) and C-peptide levels 2 h after meal in T1D patients (r = 0.5723, **p < 0.01). The frequencies of PD-1CD8 Tcm cells were only negatively correlated with the levels of HbA1c (r = - 0.2992, *p < 0.05). Similarly, the frequencies of PD-1CD8 Tem were significantly decreased in intervention group (anti-mouse PD-1 mAb) compared with the control group (14.22 ± 6.455% vs 27.69 ± 9.837%, *p < 0.05). Pathologically, CD8, PD-1 and PD-L1 were strongly expressed in the islets of diabetic mice after PD-1 blockade.
It is the first report of the expression of PD-1 on CD8 Tem cells in T1D in the present study. Our observations suggest that the PD-1/PD-L1 signal pathway on CD8 Tem cells of T1D subjects might identify a new pathway for delaying the occurrence and development by inhibiting autoimmunity.
自身免疫性疾病（包括 1 型糖尿病（T1D））的慢性炎症主要由记忆 T（Tm）细胞介导，主要是效应记忆 T（Tem）细胞。淋巴细胞程序性死亡-1（PD-1）受体的作用在肿瘤和其他感染模型中已经得到了很好的研究。然而，关于 T1D 患者 CD8 Tem 细胞上 PD-1 的表达与发病机制之间的关系知之甚少。
本研究共纳入 52 例 T1D 患者和 39 名性别、年龄和种族匹配的健康对照者。从这些个体的外周血单核细胞中分离出来并通过流式细胞术进行分析。我们评估了 T1D 患者外周血和非肥胖糖尿病（NOD）小鼠脾细胞中 PD-1 CD8 记忆 T 细胞亚群的频率。我们还研究了阻断 PD-1/PD-L1 途径对 NOD 小鼠胰岛炎症的影响。
T1D 患者外周血单个核细胞中 PD-1 CD8 Tem 细胞的频率明显降低（40.73±12.72 与 47.43±15.56，*p<0.05）。与仅有一种自身抗体的患者相比，两种或两种以上自身抗体阳性的 T1D 患者 PD-1 CD8 Tem 细胞的频率降低（13.46%与 46.95±12.72%，*p<0.05）。同时，与其他组相比，两种或两种以上自身抗体的患者 PD-1 CD8 中央记忆 T（Tcm）细胞的频率也明显降低（≥2AAb 与 HC 33.1±8.92%与 43.71±11.78%，*p<0.05；≥2AAb 与 AAb-33.1±8.92%与 41.65±11.2%，*p<0.05；≥2AAb 与 1AAb 33.1±8.92%与 48.09±10.58%，***p<0.001）。PD-1CD8 Tem 细胞的频率与空腹血清 C 肽水平呈正相关（r=0.4308，*p<0.05），与 T1D 患者餐后 2 小时的 C 肽水平呈正相关（r=0.5723，**p<0.01）。PD-1CD8 Tcm 细胞的频率仅与 HbA1c 水平呈负相关（r=-0.2992，*p<0.05）。同样，与对照组（抗鼠 PD-1 mAb）相比，干预组（14.22±6.455%）中 PD-1CD8 Tem 的频率显著降低（*p<0.05）。病理上，阻断 PD-1 后，糖尿病小鼠胰岛中 CD8、PD-1 和 PD-L1 表达强烈。
这是本研究首次报道 T1D 中 CD8 Tem 细胞上 PD-1 的表达。我们的观察结果表明，T1D 患者 CD8 Tem 细胞上的 PD-1/PD-L1 信号通路可能通过抑制自身免疫来识别延迟发生和发展的新途径。
