As a proinflammatory cytokine of the interleukin-1 (IL-1) family, IL-18 plays important roles in host protection against bacterial, viral, and fungal infection. We cloned the open reading frame of snakehead (Channa argus) IL-18 (shIL-18) and found that it contained 609 base pairs and encoded 202 amino acid residues. The shIL-18 included a conserved IL-1-like family signature and two potential IL-1β-converting enzyme cutting sites; one was conserved in all analyzed IL-18s, but the other was unique to shIL-18. Unlike other IL-18s, shIL-18 also contained a predicted signal peptide. In this study, shIL-18 was constitutively expressed in all tested tissues, and its expression was induced by Aeromonas schubertii and Nocardia seriolae in the head kidney and spleen in vivo and by lipoteichoic acid, lipopolysaccharides, and polyinosinic-polycytidylic acid in head kidney leukocytes in vitro. Moreover, recombinant shIL-18 upregulated the expression of interferon-γ, IL-1β, and tumor necrosis factor-α1 and -α2 and promoted the proliferation of leukocytes. Taken together, these results showed that IL-18 played crucial roles in host defense against bacterial infection in fish, as it does in mammals.

作为白细胞介素-1 (IL-1) 家族的促炎细胞因子，IL-18 在宿主抵御细菌、病毒和真菌感染方面发挥着重要作用。我们克隆了蛇头（Channa argus）IL-18（shIL-18）的开放阅读框，发现它含有609个碱基对，编码202个氨基酸残基。shIL-18 包括一个保守的 IL-1 样家族特征和两个潜在的 IL-1β 转换酶切割位点；一个在所有分析的 IL-18 中都是保守的，但另一个是 shIL-18 所独有的。与其他 IL-18 不同，shIL-18 还包含预测的信号肽。在本研究中，shIL-18 在所有受试组织中均组成型表达，其表达是由舒伯特气单胞菌和诺卡氏菌在头部肾脏和脾脏中诱导表达的。体内和体外头肾白细胞中的脂磷壁酸、脂多糖和聚肌苷酸。此外，重组shIL-18上调干扰素-γ、IL-1β和肿瘤坏死因子-α1和-α2的表达，促进白细胞增殖。综上所述，这些结果表明 IL-18 在宿主防御鱼类细菌感染方面发挥着至关重要的作用，就像在哺乳动物中一样。