Interleukin-12 and peripheral blood invariant natural killer T cells as an axis in childhood asthma pathogenesis

Interleukin-12 (IL-12) is a key cytokine involved in regulating the balance between TH1 and TH2 cells by promoting TH1 response. A reduced capacity to produce this cytokine could lead to aberrant TH2 development. On the same aspect significant impact of IL-12 on invariant natural killer T (iNKT) cells was reported. Therefore, we examined the serum levels of IL-12 and the absolute number of peripheral blood iNKT cells from 37 children with controlled asthma and 11 normal controls (age-matched) and correlating these two parameters with clinical asthma severity and Pulmonary function tests (PFTs). A significant decrease of serum levels of IL-12 and peripheral iNKT cells was found in total asthmatic cases compared with normal controls. This significant decrease of IL-12 levels was observed in severe asthmatic patients compared with mild and moderate cases. Serum levels of IL-12 and the numbers of peripheral iNKT cells were positively correlated with PFTs in both total asthmatic groups and in children with severe persistent asthma. Inverse correlation was found between serum level of IL-12 and different degrees of asthma. Whereas the numbers of peripheral blood iNKT cells showed no significant difference between clinical asthma severities. Impaired IL-12 production in asthmatic children beside decreasing the number of peripheral blood iNKT cells could be considered as a key component in asthma pathogenesis and hence their therapeutic manipulation may be of help in asthma management.