Lamprey (Lethenteron japonicum) IL-17 upregulated by LPS-stimulation in the skin cells
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We report here the first evidence for interleukin-17, a pro-inflammatory cytokine, in cyclostomes. To detect the novel molecules involved in the immune response in the skin of the lamprey Lethenteron japonicum, subtractive hybridization was performed with 6-h-cultured skin cells with or without lipopolysaccharide (LPS). In approximately 100 partially sequenced clones analyzed, we identified an interesting sequence similar to that of the IL-17 genes in teleosts and mammals. Subsequent rapid amplification of cDNA ends was used to obtain the cDNA of lamprey IL-17 (LampIL-17) that contains a 519-bp open reading frame encoding a mature protein of 154 amino acids and a 19-residue NH2-terminal signal peptide. The phylogenetic tree indicated that LampIL-17 is clustered into IL-17D, which is a subgroup of the IL-17 family. Southern blot analysis showed that the lamprey harbors a single copy of the LampIL-17 gene in its genome. The LampIL-17 gene was constitutively expressed in most tissues examined as well as in the skin, where the basal layer epithelial cells expressed LampIL-17 mRNA. Real-time-polymerase chain reaction (RT-PCR) demonstrated that the LampIL-17 gene expression in LPS-stimulated skin cells tended to be greater than that in non-stimulated cells. These results suggest that LampIL-17 is responsible for defense against bacterial infections in the lamprey skin.