Eosinophilia, interleukin-5, and tumour necrosis factor-alpha in asthmaticchildren

Background: There are few paediatric studies of the interrelationships betw een inflammatory markers and asthma severity. We therefore assessed the rel ationships between eosinophil-associated markers, cytokines, and asthma sev erity in asthmatic children aged 8-12 years. Methods: Forty-five children were tested twice, 2 weeks apart. Asthma sever ity was measured in terms of symptoms, lung function, medication needs, and histamine responsiveness. Peripheral inflammatory markers measured include d eosinophil numbers, serum ECP, IL-5, and TNF-alpha and mononuclear cell I L-5, and TNF-alpha production. Results: Histamine responsiveness was correlated with circulating eosinophi ls (r = 0.56, P = 0.0001) and serum ECP (r = 0.54, P = 0.003). Eosinophilia was increased in children with severe as opposed to mild airway hyperrespo nsiveness (P = 0.02) and those who lost days at school as opposed to those who did not (P = 0.01). There were no other associations between markers of asthma severity and inflammation. Children taking inhaled corticosteroids had lower serum IL-5 levels than those on beta -agonists +/- cromolyn (mean and 95% CI: 20.5 [11.7-35.7] pg/ml vs 64.3 [26.6-155.4] pg/ml; P = 0.04). Cellular IL-5 production correlated with serum TNF-alpha (r = 0.63, P = 0.0 062) and IL-5 (r = - 0.59, P = 0.005). Conclusions: Serum levels of TNF-alpha and IL-5 were not related to periphe ral eosinophilia and asthma severity in these children but were related to their own cellular production ex vivo. This study confirms that eosinophili a is the index of inflammation that is most closely related to the clinical severity of childhood asthma.