The role of IL-18 in Th1/Th2 balance in children.

Interleukin (IL)-18 has been identified as a mediator inducing interferon gamma release from type 1 helper (Th1) cells, CD8+ T cells, and natural killer cells, synergizing with IL-12. Several studies report differential roles of IL-18; but little is known about the role of IL-18 in Th1/Th2 balance in children. The aim of this study was to evaluate the role of IL-18 in Th1- and Th2-mediated diseases of children. Serum IL-18 levels were measured in a group of patients with acute asthma exacerbation (n = 24), in a group of patients who had recently been diagnosed as type I insulin-dependent diabetes mellitus (n = 18), and in a group of healthy subjects (n = 20). The groups were compared with respect to IL-18 levels. Significantly lower serum IL-18 levels were found in patients with acute asthma (median, 8.55 pg/mL) and insulin-dependent diabetes mellitus (median, 7.20 pg/mL) than in control subjects (median, 140.10 pg/mL; p < 0.05 and p < 0.001, respectively). We suggest that IL-18 may play an immunoregulatory role in allergic and autoimmune diseases and decreased expression of IL-18 can shift the immune responses to both Th1- and Th2-mediated ways.