Serum interleukins 12 and 18 and immunoglobulin E concentrations and allergic symptoms in Japanese schoolchildren.

BACKGROUND There is considerable concern about the rising trend in the prevalence of asthma and allergic diseases. The ability to monitor this trend would be enhanced by the use of a biological marker for these diseases. OBJECTIVE This study investigated whether serum interleukin (IL) 12 and IL-18 levels were associated with allergic symptoms such as those of asthma, allergic rhinitis, and atopic eczema in Japanese schoolchildren. METHODS Allergic symptoms and serum IL-12, IL-18, and immunoglobulin (Ig) E levels were examined in 370 schoolchildren aged 9-10 years living in urban Japanese areas. Allergic symptoms were assessed with a questionnaire designed in accordance with the protocol of the International Study of Asthma and Allergies in Childhood (ISAAC). RESULTS Serum IL-12 levels in children were not associated with any allergic symptoms. However, serum IL-18 levels were significantly higher in children who had asthma, allergic rhinitis, or atopic eczema than in those who did not have such symptoms. Serum IL-18 levels were also significantly higher in children with IgE levels of 250 IU/mL or above than in those with levels below 250 IU/mL. Gender-adjusted serum IL-18 levels were still significantly higher in children with allergic rhinitis, atopic eczema, or at least one allergic symptom than in those without symptoms. CONCLUSION These results suggest that serum IL-18 levels are associated with allergic symptoms in children, independent of serum IgE levels. Thus, serum IL-18 may be a useful biological marker of these diseases.