Molecular and immunological characterizations of interleukin-11 in large yellow croaker (Larimichthys crocea)

Interleukin (IL)-11 is a multifunctional cytokine that exerts a series of important immunomodulatory effects and exists in many tissues and cells. A 1106-bp nucleotide sequence representing the complete cDNA of IL-11 was obtained from large yellow croaker (Larimichthys crocea), containing an open reading frame (ORF) of 603 bp encoding for 200 amino acids (aa). The predicted LcIL-11 protein included a 12aa signal peptide and a conserved IL-11 domain. The polypeptide sequence identities between LcIL-11 and its counterparts in mammals and other fish are from 84% to 92% with known fish IL-11a and 22%-27% with fish IL-11b. LcIL-11 mRNA existed in most tissues with the most predominant expression in the gill. After immune challenge, the expression levels of LcIL-11 were induced largely in vivo and in vitro, with the peak-value of 32 times as much as the control in the liver at 24 h after Vibrio parahaemolyticus injection (p < 0.05) and the greatest value of 13.9 times as much as the control in LCK cells at 12 h after poly I:C stimulation (p < 0.05). Furthermore, the overexpression vector pcDNA3.1-LcIL-11 was constructed and transfected to LCK cells. Our results showed that the transcriptional expression levels of tumor necrosis factor (TNF)-α and myxovirus resistant protein (Mx) significantly up-regulated in LCK cells after LcIL-11 overexpression (p < 0.05). However, no significant changes of IL-1β, janus kinase (JAK)2 and signal transducers and activators of transcription (STAT)5 was detected. Our finding indicated that LcIL-11 might enhance TNF-α and antiviral protein Mx expression in large yellow croaker.