免疫肿瘤学研究揭示了免疫细胞在诱导和消除癌症中的矛盾作用。由肿瘤浸润淋巴细胞表达的程序性细胞死亡蛋白 1 (PD1) 和由肿瘤细胞表达的程序性细胞死亡配体 1 (PDL1) 是调节抗肿瘤适应性免疫反应的免疫检查点蛋白。本研究旨在验证犬组织中市售的 PDL1 抗体，然后应用人类病理学中使用的标准化方法和评分系统，评估不同类型犬肿瘤中的 PDL1 免疫阳性情况。为了证明交叉反应性，通过蛋白质印迹测试了单克隆抗体 (22C3) 和多克隆抗体（编码 A1645）。在犬组织细胞提取物中观察到两种抗体的交叉反应性；然而，多克隆抗体（编码 A1645）表现出更高的信号特异性。根据已知表达 PDL1 的人类对应物选择犬肿瘤组织型。使用多克隆抗 PDL1 抗体对 168 个肿瘤进行了免疫组织化学分析。仅膜标记被认为是阳性的。在肿瘤细胞和浸润性免疫细胞中均检测到 PDL1 标记。以下肿瘤呈免疫阳性：黑色素瘤（17 个中的 17 个；100%）、肾细胞癌（17 个中的 4 个；24%）、鳞状细胞癌（17 个中的 3 个；18%）、淋巴瘤（14 个中的 2 个；14%）、尿路上皮癌（18 例中的 2 例；11%）、肺癌（20 例中的​​ 2 例；10%）和乳腺癌（31 例中的 1 例；3%）。胃癌（10 例中有 0 例；0%）和肠癌（24 例中有 0 例；0%）呈阴性。这项研究的结果表明，PDL1 在一些犬类肿瘤中表达，其中在黑色素瘤中的患病率较高。

Immuno-oncology research has brought to light the paradoxical role of immune cells in the induction and elimination of cancer. Programmed cell death protein 1 (PD1), expressed by tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PDL1), expressed by tumor cells, are immune checkpoint proteins that regulate the antitumor adaptive immune response. This study aimed to validate commercially available PDL1 antibodies in canine tissue and then, applying standardized methods and scoring systems used in human pathology, evaluate PDL1 immunopositivity in different types of canine tumors. To demonstrate cross-reactivity, a monoclonal antibody (22C3) and polyclonal antibody (cod. A1645) were tested by western blot. Cross-reactivity in canine tissue cell extracts was observed for both antibodies; however, the polyclonal antibody (cod. A1645) demonstrated higher signal specificity. Canine tumor histotypes were selected based on the human counterparts known to express PDL1. Immunohistochemistry was performed on 168 tumors with the polyclonal anti-PDL1 antibody. Only membranous labeling was considered positive. PDL1 labeling was detected both in neoplastic and infiltrating immune cells. The following tumors were immunopositive: melanomas (17 of 17; 100%), renal cell carcinomas (4 of 17; 24%), squamous cell carcinomas (3 of 17; 18%), lymphomas (2 of 14; 14%), urothelial carcinomas (2 of 18; 11%), pulmonary carcinomas (2 of 20; 10%), and mammary carcinomas (1 of 31; 3%). Gastric (0 of 10; 0%) and intestinal carcinomas (0 of 24; 0%) were negative. The findings of this study suggest that PDL1 is expressed in some canine tumors, with high prevalence in melanomas.