【摘要】 白细胞介素-21 (interleukin-21, IL-21)是共同γ链细胞因子家族的成员，在抵御多种炎症性和免疫性疾病中发挥重要作用。为了探究大口黑鲈(Micropterus salmoides) IL-21在抵御病原菌感染后的免疫应答功能，本研究克隆了大口黑鲈MsIL-21基因(GenBank No. XP＿038555572.1)的ORF，并进行了生物信息学和表达分析。结果显示，MsIL-21的ORF全长为441 bp，编码146个氨基酸。序列分析发现，MsIL-21具有IL-21蛋白的典型结构，包括4组α-螺旋和4个半胱氨酸残基。同源性分析发现，Ms IL-21与欧洲海鲈(Dicentrarchus labrax) IL-21的亲缘关系最近。qPCR分析表明，MsIL-21在健康大口黑鲈组织中普遍表达，在肝脏中表达最高。经过维氏气单胞菌(Aeromonas veronii)和鰤诺卡氏菌(Nocardia seriolae)感染后，MsIL-21在肝脏、头肾和脾脏中表达均上调。采用病原类似物脂多糖(lipopolysaccharide, LPS)、脂磷壁酸(lipoteichoic acid, LTA)和聚肌胞苷酸(polyinosinic-polycytidylic acid, Poly(I:C))刺激头肾白细胞均可诱导MsIL-21的表达。通过原核表达系统，成功表达和纯化了MsIL-21蛋白。MsIL-21蛋白刺激头肾白细胞可诱导IL-10、IL-22、IL-1β和干扰素-γ (interferon-γ, IFN-γ)的表达。综上，本研究初步证明MsIL-21可能参与抵御病原菌感染，进一步丰富了鱼类IL-21的功能研究。更多还原

【Abstract】 Interleukin-21(IL-21) is a member of the common gamma chain(γc) cytokine family and plays an important role in defense against a variety of inflammatory and immune diseases. In order to explore the immune response function of IL-21 against pathogen infection, in this study, the ORF of largemouth bass(Micropterus salmoides) MsIL-21(GenBank No. XP＿038555572.1) was cloned, and bioinformatics and expression analysis were performed. The results showed that the full length of MsIL-21 ORF was 441 bp and encoding 146 amino acids. Sequence analysis revealed that MsIL-21 had the typical structure of IL-21 protein,including 4 groups of α-helices and 4 cysteine residues. Homology analysis revealed that MsIL-21 was most closely related to IL-21 of European sea bass(Dicentrarchus labrax). qPCR analysis showed that MsIL-21 was commonly expressed in all the healthy largemouth bass tissues tested, with the highest expression in the liver.After infection with Aeromonas veronii or Nocardia seriolae, the up-regulation of expression was detected in the liver, head kidney, and spleen. Similarly, after stimulation with pathogenic analogs lipopolysaccharide(LPS),lipoteichoic acid(LTA), and polyinosinic-polycytidylic acid [Poly(I: C)], the expression of MsIL-21 could be induced in head kidney leukocytes. The recombinant MsIL-21 protein was expressed and purified by prokaryotic expression system, which induced the expression of IL-10, IL-22, IL-1β, and interferon-γ(IFN-γ)in head kidney leukocytes. Taken together, the present study initially suggests that MsIL-21 may be involved in defense against pathogenic bacterial invasion and infection. This study further enriches the functional studies of fish IL-21.更多还原