Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Infectology, 17493 Greifswald-Insel Riems, Germany.
Dev Comp Immunol. 2011 Jul;35(7):752-63. doi: 10.1016/j.dci.2011.02.008. Epub 2011 Feb 23.
CD8, belonging to the TCR complex, is the main marker molecule of CTLs. Although CD8 genes have been detected in many fish species, the analysis of teleost CD8+ cells has been limited because of the lack of antibodies. Using newly established mAbs against rainbow trout CD8α, we found high ratios of CD8α+ cells in trout thymus, gill and intestine, but relatively low abundance in pronephros, spleen and blood. Accordingly, tissue sections revealed many CD8α+ cells in thymus, numerous intra- and subepithelial CD8α+ cells in intestine and gill and few scattered CD8α+ cells in spleen and pronephros. In secondary lymphoid tissues, CD8α+ lymphocytes, which did not react with anti-thrombocyte or anti-IgM mAbs, expressed CD8α, CD8β and TCRα, while Ig and CD4 transcripts were found in CD8α⁻ lymphocytes. In contrast, considerable CD4 expression in CD8α+ thymocytes suggests the presence of double-positive early T cells. Highly expressed TCRγ, LAG3 and CTLA4 in CD8α+ lymphocytes imply that they constitute a heterogeneous population different from found in non-mucosal tissues. PHA stimulation resulted in an up-regulation of CTL effector genes (perforin, granulysin and IFN-γ) in CD8α+ pronephrocytes, while both Th1 (IFN-γ) and Th2 (IL-4/13A) cytokines were up-regulated in CD8α⁻ pronephrocytes. Although the basic characteristics of CD8α+ lymphocytes seem similar in teleost and mammals, features such as the low proportion of teleost CD8α+ lymphocytes in blood and their high abundance in respiratory tissue reveal a unique dynamics and distribution.
CD8 属于 TCR 复合物，是 CTL 的主要标记分子。尽管在许多鱼类物种中都检测到了 CD8 基因，但由于缺乏抗体，对硬骨鱼类 CD8+细胞的分析受到限制。我们使用新建立的抗虹鳟鱼 CD8α 的 mAb，发现 CD8α+细胞在虹鳟鱼胸腺、鳃和肠道中的比例较高，但在肾前体、脾脏和血液中的丰度较低。因此，组织切片显示胸腺中有许多 CD8α+细胞，肠道和鳃中有大量的上皮内和上皮下 CD8α+细胞，而脾脏和肾前体中只有少量散在的 CD8α+细胞。在次级淋巴组织中，不与抗血小板或抗 IgM mAb 反应的 CD8α+淋巴细胞表达 CD8α、CD8β 和 TCRα，而 CD8α−淋巴细胞中则发现 Ig 和 CD4 转录物。相比之下，CD8α+胸腺细胞中大量表达 CD4 表明存在双阳性早期 T 细胞。CD8α+淋巴细胞中高度表达的 TCRγ、LAG3 和 CTLA4 表明它们构成了一个不同于非黏膜组织的异质群体。PHA 刺激导致 CD8α+肾前体细胞中 CTL 效应基因（穿孔素、颗粒酶和 IFN-γ）的上调，而 Th1（IFN-γ）和 Th2（IL-4/13A）细胞因子在 CD8α−肾前体细胞中均上调。尽管硬骨鱼类 CD8α+淋巴细胞的基本特征在硬骨鱼类和哺乳动物中似乎相似，但硬骨鱼类 CD8α+淋巴细胞在血液中的比例较低，在呼吸组织中的丰度较高等特点揭示了其独特的动态和分布。
