Molecular cloning of feline interferon-gamma-inducing factor (interleukin-18) and its expression in various tissues

Interleukin-18 (IL-18) is a cytokine with potent interferon-gamma -inducing activity, and plays an important biologic role in the enhancement of the a ctivity of natural killer cells and cytotoxic T-lymphocytes. In this study, feline IL-18 cDNA was cloned and characterized to establish a basis for th e prospective cytokine therapy in small animal practice. The nucleotide seq uence of feline IL-18 cDNA obtained in this study was 712 bp long and conta ined its entire open reading frame encoding 192 amino acid residues. The pr edicted amino acid sequence of feline IL-18 cDNA showed 77.2, 84.8, 60.2 an d 62.6% similarity with those of human, dog, rat and mouse counterparts, re spectively. The feline IL-18 cDNA included a putative cleavage site of IL-1 beta -converting enzyme (ICE) and IL-1 signature-like sequences identified in human and mouse IL-18 cDNAs. Expression of IL-18 mRNA was detected in v arious tissues including spleen, liver and cerebrum in the cat. (C) 2001 Pu blished by Elsevier Science B.V.