Interleukin-6 (IL-6) is a pleiotropic cytokine with crucial immunoregulatory functions in both innate and adaptive immune responses. However, the IL-6 sequence and function remain unknown in sturgeon, one chondrostean fish. In the present study, we identified an interleukin-6 homolog from Siberian sturgeon (Acipenser baeri), named AbIL-6. Its open reading frame (ORF) was 657 nucleotides in length, encoding a polypeptide of 218 amino acids, which contains a signal peptide and the IL-6 family domain. Phylogenetic analysis showed that sturgeon IL-6 had close relationship with both teleost and chondrichthyes IL-6s. Abil-6 mRNA was highly expressed in spleen, brain and liver tissues of healthy sturgeon, and significantly up-regulated in the spleen, head kidney and liver by A.hydrophila (A.h) challenge. Heat-killed A.h and LPS effectively stimulated Abil-6 transcripts in primary spleen cells in vitro. In order to understand the bioactivity and influence of AbIL-6 on immune responses, recombinant AbIL-6 (rAbIL-6) was synthesized by prokaryotes and demonstrated to promote the proliferation of spleen cells and head kidney cells in vitro. Additionally, intraperitoneal injection of rAbIL-6 induced significantly higher expression of four immuno-related genes including il-1β, cxcl10, mhcIIβ and igm. rAbIL-6 improved the survival rate and reduced the tissue bacterial load after A.h infection. Taken together, these results suggest that AbIL-6 plays an important role in inflammatory responses and immune defense against bacterial infection of sturgeon.

中文翻译：

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西伯利亚st（Acipenser baeri）中的白介素6：分子表征和免疫功能活性。

白细胞介素6（IL-6）是一种多效性细胞因子，在先天和适应性免疫应答中均具有关键的免疫调节功能。然而，IL-6的序列和功能在st鱼（一种软骨鱼类）中仍然未知。在本研究中，我们鉴定了来自西伯利亚st（Acipenser baeri）的白细胞介素6同源物，命名为AbIL-6。它的开放阅读框（ORF）长657个核苷酸，编码218个氨基酸的多肽，其中包含一个信号肽和IL-6家族结构域。系统发育分析表明st鱼IL-6与硬骨鱼和软骨鱼类IL-6s密切相关。Abil-6 mRNA在健康st鱼的脾脏，大脑和肝脏组织中高表达，并在嗜水嗜碱杆菌（Ahophila，Ah）刺激下在脾脏，头部肾脏和肝脏中显着上调。热销的A. h和LPS在体外能有效刺激原代脾细胞中的Abil-6转录本。为了了解AbIL-6的生物活性和对免疫应答的影响，原核生物合成了重组AbIL-6（rAbIL-6），并证明了其在体外能促进脾细胞和头肾细胞的增殖。另外，腹膜内注射rAbIL-6诱导四个免疫相关基因的高表达，包括il-1β，cxcl10，mhcIIβ和igm。rAbIL-6提高了Ah感染后的存活率并降低了组织细菌负荷。综上所述，这些结果表明AbIL-6在针对鱼细菌感染的炎症反应和免疫防御中起重要作用。为了了解AbIL-6的生物活性和对免疫应答的影响，原核生物合成了重组AbIL-6（rAbIL-6），并证明了其在体外能促进脾细胞和头肾细胞的增殖。另外，腹膜内注射rAbIL-6诱导四个免疫相关基因的高表达，包括il-1β，cxcl10，mhcIIβ和igm。rAbIL-6提高了Ah感染后的存活率并降低了组织细菌负荷。综上所述，这些结果表明AbIL-6在针对鱼细菌感染的炎症反应和免疫防御中起重要作用。为了了解AbIL-6的生物活性和对免疫应答的影响，原核生物合成了重组AbIL-6（rAbIL-6），并证明了其在体外能促进脾细胞和头肾细胞的增殖。另外，腹膜内注射rAbIL-6诱导四个免疫相关基因的高表达，包括il-1β，cxcl10，mhcIIβ和igm。rAbIL-6提高了Ah感染后的存活率并降低了组织细菌负荷。综上所述，这些结果表明AbIL-6在针对鱼细菌感染的炎症反应和免疫防御中起重要作用。腹膜内注射rAbIL-6诱导四种免疫相关基因的高表达，包括il-1β，cxcl10，mhcIIβ和igm。rAbIL-6提高了Ah感染后的存活率并降低了组织细菌负荷。综上所述，这些结果表明AbIL-6在针对鱼细菌感染的炎症反应和免疫防御中起重要作用。腹膜内注射rAbIL-6诱导四种免疫相关基因的高表达，包括il-1β，cxcl10，mhcIIβ和igm。rAbIL-6提高了Ah感染后的存活率并降低了组织细菌负荷。综上所述，这些结果表明AbIL-6在针对鱼细菌感染的炎症反应和免疫防御中起重要作用。