Evaluation of Costimulatory Molecules in Peripheral Blood Lymphocytes of Canine Patients with Histiocytic Sarcoma

Histiocytic sarcoma is a rapidly progressive and fatal neoplastic disease in dogs. It is unclear whether costimulatory molecules, including CD28, cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), and programmed death-1 (PD-1), are expressed on peripheral blood lymphocytes (PBLs) of canine patients with histiocytic sarcoma. The objective of this study was to evaluate the expression of CD28, CTLA-4, and PD-1 molecules on PBLs of patients with histiocytic sarcoma, patients with other tumors, and healthy controls. Twenty-six dogs were included in the study, with eight, ten, and eight dogs in the histiocytic sarcoma, other tumor, and healthy control groups, respectively. PBLs and serum were prospectively obtained from patients diagnosed histopathologically with histiocytic sarcoma, other tumors and healthy controls. The surface expression of CTLA-4, CD28, and PD-1 on T lymphocytes was examined using flow cytometric analysis. Serum samples were frozen at −30°C until serum interferon-γ (IFN-γ) was measured by enzyme-linked immunosorbent assay. The expression level of CTLA-4 on CD4+ lymphocytes was significantly higher in the histiocytic sarcoma group than in the control group. The expression of CTLA-4 on CD8+ lymphocytes was significantly higher in the histiocytic sarcoma group than in the other two groups. In addition, the expression of PD-1 on CD8+ lymphocytes was significantly higher in the histiocytic sarcoma group than in the control group. However, no significant differences in CD28 expressions and serum IFN-γ levels were observed. The present results provided evidence showing that the expression levels of CTLA-4 on both CD4+ and CD8+ lymphocytes and PD-1 on CD8+ lymphocytes in peripheral blood obtained from dogs with histiocytic sarcoma were upregulated. The overexpressions of CTLA 4 and PD-1 suggested that antitumor immunity may be suppressed in dogs with histiocytic sarcoma.组织细胞肉瘤（Histiocytic sarcoma）是一种发生于犬类的快速进展性致死性肿瘤性疾病。目前尚不明确CD28、细胞毒性T淋巴细胞相关抗原4（CTLA-4）以及程序性死亡受体1（PD-1）这类共刺激分子，是否在组织细胞肉瘤患犬的外周血淋巴细胞（PBLs）表面表达。本研究旨在评估组织细胞肉瘤患犬、其他肿瘤患犬及健康对照犬的外周血淋巴细胞中CD28、CTLA-4与PD-1分子的表达水平。本研究共纳入26只犬，其中组织细胞肉瘤组、其他肿瘤组与健康对照组分别包含8只、10只与8只犬。本研究前瞻性地从经组织病理学确诊的组织细胞肉瘤患犬、其他肿瘤患犬及健康对照犬体内采集外周血淋巴细胞与血清样本。采用流式细胞术分析检测T淋巴细胞表面CTLA-4、CD28与PD-1的表达情况。血清样本于−30℃条件下冻存，后续通过酶联免疫吸附试验检测血清干扰素γ（IFN-γ）水平。结果显示，组织细胞肉瘤组CD4阳性淋巴细胞表面CTLA-4的表达水平显著高于健康对照组；组织细胞肉瘤组CD8阳性淋巴细胞表面CTLA-4的表达水平显著高于另外两组。此外，组织细胞肉瘤组CD8阳性淋巴细胞表面PD-1的表达水平显著高于健康对照组。但未观察到CD28表达及血清IFN-γ水平存在显著差异。本研究结果证实，组织细胞肉瘤患犬外周血中CD4阳性与CD8阳性淋巴细胞表面CTLA-4的表达水平，以及CD8阳性淋巴细胞表面PD-1的表达水平均出现上调。CTLA-4与PD-1的过表达提示，组织细胞肉瘤患犬体内的抗肿瘤免疫功能可能受到抑制。