Interleukin-18 is associated with the severity of atopic dermatitis

Interleukin (IL)-18 acts as both a Th1 and Th2 cytokine, but its association with allergic diseases remains unclear. The aim of the present study was to measured plasma IL-18 and serum IgE levels in atopic children to evaluate how IL-18 is associated with allergic diseases. The plasma IL-18 and serum IgE levels in 51 atopic children, 28 healthy control children and 14 healthy control adults were measured by enzyme-linked immunosorbent assay (ELISA). The 5' end of the IL-18 gene of 48 atopic children and 20 healthy control children was sequenced. The plasma IL-18 level was significantly elevated in children with bronchial asthma and/or atopic dermatitis. Plasma IL-18 levels in the moderate or severe atopic dermatitis group were significantly higher than those in either the control group or the mild atopic dermatitis group. There was a positive correlation between plasma IL-18 and serum IgE levels. Three allelic combinations of polymorphisms in the IL-18 gene promoter region were observed. There was no significant difference in the plasma IL-18 levels between groups carrying these genotypes. However, bronchial asthma patients had significantly higher frequencies of the − 137 G/G genotype than did control children. The plasma IL-18 level was elevated, particularly in patients with atopic dermatitis. As the clinical severity of atopic dermatitis increased, the plasma IL-18 level also tended to increase. These findings suggest that IL-18 may be associated with the severity of atopic dermatitis.