IL18 and chronic obstructive pulmonary disease: The allele IL18-607C has been linked to hepatitis C susceptibility [30] and chronic obstructive pulmonary disease [31], and the genotype C/C has been associated with higher IL-18 production in multiple sclerosis [32]; IL18-137G was associated with the risk of arthritis [10] and IL18-137G/C genotype with oral cancer [12].