CD27 is a member of tumor necrosis factor receptor superfamily, and plays a central role in B cell-mediated immune response in mammals. However, the functional characterization of CD27 molecule remains unclear in bony fish. In this study, the CD27 molecule of Nile tilapia (OnCD27) was cloned and its functional characterization was identified by pursuing the expression patterns in T cell-dependent (TD) response and B cell differentiation process. The open reading frame (ORF) of OnCD27 is 666 bp of the nucleotide sequence, encoding a protein of 221 amino acid including two TNFR domains in the extracellular region. Bioinformatics analysis indicated that OnCD27 was highly homologous to other bony fish and similar to mammals. Tissue distribution analysis displayed that the relative expression of OnCD27 was highest in spleen among the examined tissues. The OnCD27 expression was significantly up-regulated in spleen and head kidney post-challenge of a TD antigen keyhole limpet hemocyanin (KLH) in vivo. Following recombination Oreochromis niloticus IL10 ((r)OnIL10) protein stimulation in vitro, the up-regulation of OnCD27 expression was detected during the process of B cell differentiation. Further, analysis of OnCD27 expression in different B cell subsets revealed that the OnCD27 expression in P50 plasma-like cells was remarkable higher than P60 plasmablast-like and P70 naïve mature B cells. Moreover, the OnCD27 transcripts presented a higher expression level in IgM^lo plasma-like cells than IgM^hi activated B cells. In summary, the collective results may provide that OnCD27 plays roles in T cell-dependent response and B cell differentiation in Nile tilapia.

CD27 是肿瘤坏死因子受体超家族的成员，在哺乳动物的 B 细胞介导的免疫反应中起核心作用。然而，CD27 分子的功能特征在硬骨鱼中仍不清楚。在这项研究中，克隆了尼罗罗非鱼 (OnCD27) 的 CD27 分子，并通过追踪 T 细胞依赖性 (TD) 反应和 B 细胞分化过程中的表达模式来鉴定其功能特征。OnCD27 的开放阅读框 (ORF) 是 666 bp 的核苷酸序列，编码 221 个氨基酸的蛋白质，包括胞外区的两个 TNFR 结构域。生物信息学分析表明，OnCD27与其他硬骨鱼高度同源，与哺乳动物相似。组织分布分析表明OnCD27的相对表达在检查的组织中脾脏中最高。所述OnCD27表达显著在TD抗原匙孔血蓝蛋白（KLH）的脾和头肾攻击后上调体内。在体外重组Oreochromis niloticus IL10 ((r)OnIL10) 蛋白刺激后，在B 细胞分化过程中检测到OnCD27表达的上调。此外，对不同 B 细胞亚群中 OnCD27 表达的分析表明，P50 浆样细胞中的OnCD27表达显着高于 P60 浆母细胞样和 P70 幼稚成熟 B 细胞。此外，OnCD27转录物在 IgM ^lo浆样细胞中的表达水平高于 IgM ^hi激活的 B 细胞。总之，集体结果可能表明 OnCD27 在尼罗罗非鱼的 T 细胞依赖性反应和 B 细胞分化中起作用。