Cloning, sequencing, and expression of porcine interleukin-18 in Escherichia coli

IL-18 is the new name of a novel cytokine that plays an important role in T_H1 response, primarily by its ability to induce IFN-γ production in T cells and natural killer cells. The porcine IL-18 gene was isolated using RT-PCR from porcine alveolar macrophages. Sequence analysis of the porcine IL-18 gene has demonstrated an open reading frame of 579 base pairs encoding 192 amino acids precursor protein with a predicted molecular mass of 22 kDa. The porcine IL-18 gene shares 84% and 89% similarity to the human and canine equivalents, respectively, at the nucleotide level. The cloned IL-18 was expressed in Escherichia coli and its expression was confirmed by SDS-PAGE and Western blotting.