Serum OX40 ligand levels in asthmatic children: a potential biomarker of severity and persistence.

The costimulatory molecule OX40 and its ligand, OX40L, mediate key aspects of allergic airway inflammation in animal models of asthma, including eosinophilic airway inflammation, airway hyperresponsiveness, and T-helper type 2 (Th2) polarization. However, involvement of these molecules in Th2-dominated allergen-induced childhood asthma remains unclear. Therefore, we sought to examine OX40L expression in pediatric asthma across disease activity and attack severity. Serum OX40L concentrations were measured by ELISA in 50 children with atopic asthma (during and in between acute attacks), and in 40 healthy children serving as controls. The median and mean (SD) serum OX40L levels (1487 and 1560 [543] pg/mL) were significantly higher in asthmatic children during acute attacks in comparison with children in between attacks (731 and 689 [321] pg/mL) and in comparison with controls (193 and 157 [60.3] pg/mL). OX40L values were higher among children who presented with acute severe asthma exacerbations than in children with mild or moderate asthma exacerbations. During stability, patients with severe persistent asthma had significantly higher levels when compared with patients with moderate or mild persistent asthma. A positive correlation could be elicited between OX40L levels during exacerbations and the corresponding values during remission. Serum OX40L levels correlated negatively with peak expiratory flow rate and positively with absolute eosinophil count. Up-regulation of OX40L may play a critical role in development of childhood atopic asthma and is in favor of asthma severity. OX40L may represent a useful biomarker of monitoring allergic inflammation. OX40L is one of the most promising targets of immune intervention for treatment of these diseases.