Stein V M, Baumgärtner W, Schröder S, Zurbriggen A, Vandevelde M, Tipold A
Department of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, Hannover, Germany.
J Vet Med A Physiol Pathol Clin Med. 2007 Aug;54(6):314-20. doi: 10.1111/j.1439-0442.2007.00926.x.
CD45, also called leucocyte common antigen is a transmembrane protein tyrosine phosphatase on the surface of nearly all white blood cells and has a functional role in signal transduction. In the brain, the expression of CD45 can be used to distinguish microglial cells with a characteristic phenotype of CD11b/c+ and CD45(low) from other central nervous system (CNS) macrophages which show an expression of CD11b/c+ and CD45(high). In the course of pathological changes in the CNS, microglia in rodents is known to readily upregulate expression of various surface molecules, such as CD45. Understanding the mechanisms that regulate expression of surface molecules is essential to study the pathogenesis of CNS diseases. In the present study, the expression of CD45 on microglia of 42 dogs was examined ex vivo by means of flow cytometry. The dogs were classified in two groups according to the histopathological diagnosis in the CNS. All dogs without changes in the CNS (group I; n = 22) only showed low percentages of CD45+ microglial cells. In group II consisting of 20 dogs with different intracranial diseases varying results were obtained. Thirteen dogs showed a low percentage of CD45+ microglial cells whereas seven dogs exhibited high percentages of microglial cells expressing CD45. Evaluation of expression intensity in these seven dogs revealed two subpopulations of CD45+ microglial cells: a large subpopulation with CD45(low) and a small subpopulation with CD45(high). The expression intensity of CD45(high) was comparable with that of canine monocytes. It was attempted to correlate these findings to age of the animals, underlying disease, duration of clinical signs, medical treatment, occurrence of seizure activity and the expression of other surface molecules. It appeared that dogs with high percentages of CD45+ suffered from long-lasting CNS disease with seizures. In future studies, the reason and consequences for upregulated CD45 in long-lasting CNS diseases has to be further evaluated.
CD45，也称为白细胞共同抗原，是几乎所有白细胞表面的一种跨膜蛋白酪氨酸磷酸酶，在信号转导中发挥功能作用。在大脑中，CD45的表达可用于区分具有CD11b/c+和CD45（低）特征表型的小胶质细胞与其他显示CD11b/c+和CD45（高）表达的中枢神经系统（CNS）巨噬细胞。在中枢神经系统病理变化过程中，已知啮齿动物的小胶质细胞会容易上调各种表面分子的表达，如CD45。了解调节表面分子表达的机制对于研究中枢神经系统疾病的发病机制至关重要。在本研究中，通过流式细胞术对42只犬的小胶质细胞上CD45的表达进行了体外检测。根据中枢神经系统的组织病理学诊断将犬分为两组。所有中枢神经系统无变化的犬（I组；n = 22）仅显示低百分比的CD45+小胶质细胞。在由20只患有不同颅内疾病的犬组成的II组中，获得了不同的结果。13只犬显示CD45+小胶质细胞的百分比低，而7只犬显示表达CD45的小胶质细胞百分比高。对这7只犬的表达强度评估显示CD45+小胶质细胞有两个亚群：一个CD45（低）的大亚群和一个CD45（高）的小亚群。CD45（高）的表达强度与犬单核细胞的相当。试图将这些发现与动物的年龄、潜在疾病、临床症状持续时间、药物治疗、癫痫发作活动的发生以及其他表面分子的表达相关联。似乎CD45+百分比高的犬患有伴有癫痫发作的长期中枢神经系统疾病。在未来的研究中，必须进一步评估长期中枢神经系统疾病中CD45上调的原因和后果。
