During immune activation, CD25 is expressed by T cells, and its soluble form (sCD25) is released into the extracellular matrix and the bloodstream. In humans, serum sCD25 concentrations are used as a surrogate marker for autoimmune diseases, malignancies, and transplant rejection. However, a canine-specific assay for the measurement of sCD25 in dog serum has not previously been described. Therefore, the aims of this study were to develop and analytically validate a radioimmunoassay to measure sCD25 in canine serum, to establish a reference interval for canine sCD25, and to test the clinical utility of this assay with serum samples for dogs with various diseases. A competitive radioimmunoassay (RIA) was developed and analytically validated. Analytical validation consisted of lower limit of detection (LLOD), dilutional parallelism, spiking recovery, and intra- and inter-assay variability using pooled surplus canine serum samples. A reference interval was established in healthy dogs and serum samples from dogs with various types of neoplasia, IBD, liver disease, suspected pancreatitis, or suspected small intestinal disease and serum samples with an increased C-reactive protein concentration (CRP) were analyzed to test the clinical utility of the assay. LLOD was calculated to be 0.5 ng/mL. The mean (±SD) observed-to-expected ratio (O/E) for serial dilutions was 101.7 ± 14.0%, and the mean (± SD) O/E for spiking recovery was 93.2 ± 4.2%. Coefficients of variation (CVs) for intra-assay variability were ≤12.5% (mean ± SD: 7.5 ± 4.2%), and inter-assay CVs were ≤15.7% (mean ± SD: 11 ± 4.4%). A reference interval (RI) for canine sCD25 of 1.2-4.2 ng/mL was established from a population of 112 clinically healthy dogs. Dogs with neoplasia and dogs with suspected small intestinal disease had decreased concentrations of serum sCD25 when compared to healthy dogs (p < 0.0001, respectively). However, the majority of clinical samples used in this study were within the reference interval. Median concentrations of serum sCD25 were 1.9 ng/mL for healthy dogs. Dogs with cancer, IBD, liver disease, suspected pancreatitis, or suspected small intestinal disease, as well as sera with an increased serum CRP concentration, had median serum sCD25 concentrations of 1.6 ng/mL, 2.1 ng/mL, 2.2 ng/mL, 1.7 ng/mL, 1.5 ng/mL, and 1.8 ng/mL, respectively. Thus, the RIA described here is linear, accurate, precise, and reproducible for measuring sCD25 in canine serum. However, this assay shows little clinical utility of sCD25 as a biomarker for dogs with inflammatory, autoimmune, and/or neoplastic conditions.

中文翻译：

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放射免疫分析法的发展，分析验证和初步临床评估，用于测量犬血清中的可溶性CD25浓度。

在免疫激活过程中，CD25由T细胞表达，其可溶性形式（sCD25）释放到细胞外基质和血液中。在人类中，血清sCD25浓度用作自身免疫性疾病，恶性肿瘤和移植排斥的替代标志物。然而，先前没有描述用于测量狗血清中sCD25的犬特异性测定。因此，本研究的目的是开发和分析验证放射免疫测定法，以测定犬血清中的sCD25，建立犬sCD25的参考区间，并用该血清样本对患有各种疾病的狗进行该试验的临床实用性。开发了竞争性放射免疫分析（RIA）并进行了分析验证。分析验证包括检测下限（LLOD），稀释平行度，加标回收率，以及使用合并的多余犬血清样本进行的测定内和测定间变异性。建立健康犬的参考间隔，并从患有各种类型的肿瘤，IBD，肝病，疑似胰腺炎或疑似小肠疾病的犬的血清样本中进行分析，并分析C反应蛋白浓度（CRP）升高的血清样本以进行检测测定的临床效用。LLOD经计算为0.5ng / mL。连续稀释液的平均观察值/预期值（O / E）为101.7±14.0％，加标回收率的平均（±SD）O / E为93.2±4.2％。批内变异性的变异系数（CVs）≤12.5％（平均值±SD：7.5±4.2％），批间变异CV≤15.7％（平均值±SD：11±4.4％）。犬sCD25的参考间隔（RI）为1.2-4。从112名临床健康狗的种群中确定了2 ng / mL。与健康犬相比，患有肿瘤的犬和怀疑患有小肠疾病的犬的血清sCD25浓度降低（分别为p <0.0001）。但是，本研究中使用的大多数临床样品均在参考区间内。健康犬血清sCD25的中位数浓度为1.9 ng / mL。患有癌症，IBD，肝病，疑似胰腺炎或疑似小肠疾病以及血清CRP浓度升高的狗的血清sCD25浓度中值分别为1.6 ng / mL，2.1 ng / mL，2.2 ng / mL，分别为1.7 ng / mL，1.5 ng / mL和1.8 ng / mL。因此，此处描述的RIA是线性的，准确的，精确的且可重复的，可用于测定犬血清中的sCD25。然而，