Interleukin 17 genes as mediators of inflammatory responses in Ciona intestinalis.

Inflammation is a complex reaction of host defence mechanisms aiming at neutralization of an insult and restoring normal tissue structure and function. In human IL-17 is T-cell derived cytokine plays a key role in the clearance of extracellular bacteria promoting cell infiltration and production of several cytokines and chemokines. Here, we report on three Ciona intestinalis IL-17 homologues (CiIL17-1, CiIL17-2, CiIL17-3). The gene organization, phylogenetic tree and modeling supported the close relationship with the mammalian IL-17A and IL-17F suggesting that the C. intestinalis IL-17 genes share a common ancestor in the chordate lineages. Real time PCR analysis showed a prompt expression induced by LPS inoculation showing that they are involved in the first steps of inflammatory response. In situ hybridization assays disclosed that the genes transcription was upregulated in the pharynx, the main organ of the ascidian immune system, and expressed by hemocytes (granulocytes and univacuolar refractile granulocyte) inside the pharynx vessels. As in human, we can assume that CiIL-17-like stimulates the release of CiTNFalpha, which synergizes with CiIL-17 in its effects on cells and molecules of Ciona intestinalis immunity system. In addition, a comparative evaluation with others molecules upregulated by LPS challenge as CiTNF-alpha, phenoloxisases, peroxinectin, galectins and mannan binding lectin, have been evaluated in terms of temporal and quantitative gene expression.