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. Genderadjusted 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.

Key Words: Interleukin 12, IL-12. Interleukin 18, IL-18. Immunoglobulin E, IgE. Asthma. Allergic rhinitis. Atopic eczema. Allergy. Children.