J Leukoc Biol 2003 Feb;73(2):213-24
Gracie JA, Robertson SE, McInnes IB.
Centre for Rheumatic Diseases, University of Glasgow, Scotland, United
Kingdom.
Interleukin-18 (IL-18), a recently described member of the IL-1 cytokine superfamily, is now recognized as an important regulator of innate and acquired immune responses.
IL-18 is expressed at sites of chronic inflammation, in autoimmune diseases, in a variety of cancers, and in the context of numerous infectious diseases.
This short review will describe the basic biology of IL-18 and thereafter address its potential effector and regulatory role in several human disease states including autoimmunity and infection.
IL-18, previously known as interferon-gamma (IFN-gamma)-inducing factor, was identified as an endotoxin-induced serum factor that stimulated IFN-gamma production by murine splenocytes [(1) ].
IL-18 was cloned from a murine liver cell cDNA library generated from animals primed with heat-killed Propionibacterium acnes and subsequently challenged with lipopolysaccharide [(2) ].
Nucleotide sequencing of murine IL-18 predicted a precursor polypeptide of 192 amino acids lacking a conventional signal peptide and a mature protein of 157 amino acids.
Subsequent cloning of human IL-18 cDNA revealed 65% homology with murine IL-18 [(3) ] and showed that both contain an unusual leader sequence consisting of 35 amino acids at their N terminus.