Supplementary Material for: Tumor-Infiltrating T Cells Concurrently Overexpress CD200R with Immune Checkpoints PD-1, CTLA-4, and TIM-3 in Non-Small-Cell Lung Cancer

<b><i>Introduction:</i></b> CD200R has been reported to be the receptor for the immune checkpoint molecule CD200 and can transduce immune-suppressive signals. In this study, we mainly focused on the expression level of CD200R in T cells in pulmonary artery (PA) blood and non-small-cell lung cancer (NSCLC) tumor tissue. <b><i>Methods:</i></b> Immune cells were isolated from dissected tumor samples and PA blood of NSCLC patients and analyzed with multiparameter flow cytometry. The co-expression of CD200R with other immune checkpoints, including programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), was also investigated. <b><i>Results:</i></b> CD200R expression was observed on the surface of approximately 75% of T cells among tumor-infiltrating leukocytes (TILs). Compared to T cells extracted from TILs, only 55% of T cells extracted from PA blood exhibited CD200R expression. Moreover, with higher expression of CD200R, the expression of other immune checkpoints, including PD-1, CTLA-4, and TIM-3, was also increased in tumor-infiltrating T cells compared to T cells in PA blood. <b><i>Conclusions:</i></b> Our results showed that those tumors were dominated by T cells expressing CD200R together with other checkpoints, which suggests a phenotypic change after T cell infiltration into the tumor, such as T cell exhaustion.

**<i>引言：</i>** CD200受体（CD200R）已被证实为免疫检查点分子CD200的受体，能够转导免疫抑制信号。本研究重点关注CD200R在非小细胞肺癌（NSCLC）患者肺动脉血及肿瘤组织T细胞中的表达水平。
**<i>方法：</i>** 从非小细胞肺癌患者的手术切除肿瘤样本及肺动脉血中分离免疫细胞，采用多参数流式细胞术进行分析。同时探究CD200R与程序性细胞死亡蛋白1（PD-1）、细胞毒性T淋巴细胞相关蛋白4（CTLA-4）以及T细胞免疫球蛋白黏蛋白域蛋白3（TIM-3）等其他免疫检查点的共表达情况。
**<i>结果：</i>** 在肿瘤浸润淋巴细胞（TILs）中，约75%的T细胞表面可检测到CD200R表达。相较于肿瘤浸润T细胞，肺动脉血来源的T细胞中仅55%表达CD200R。此外，与肺动脉血中的T细胞相比，肿瘤浸润T细胞内CD200R的表达水平越高，PD-1、CTLA-4及TIM-3等其他免疫检查点的表达水平也随之升高。
**<i>结论：</i>** 本研究结果表明，此类肿瘤以共表达CD200R与其他免疫检查点的T细胞为主要浸润成分，这提示T细胞浸润进入肿瘤后发生了表型改变，例如T细胞耗竭（T cell exhaustion）。