The role of eosinophils in children with asthma

Eosinophilia in asthmatic subjects is related to excessive production of Th2-type cytokines, and eosinophils play a significant role in the pathophysiology of asthma. Activated by cytokines IL-3, IL-5 and GM-CSF, eosinophils acquire a hypodense phenotype (cell density below 1.093 g/mL) and release their toxic granules containing: eosinophilic cation protein (ECP), eosinophil peroxidase (EPO), major basic protein (MBP), eosinophil derived protein neurotoxin (EDN) and eosinophil protein X (EPX). The resulting cytotoxic effects are correlated with the symptoms of asthma. Eosinophils activated by IL-5 are also involved in nonreaginic-type asthma as the inflammatory cells. In order to assess the diagnostic and screening value of tissue and peripheral blood eosinophilia, we studied these parameters in 248 children with reaginic and 129 with nonreaginic asthma. In the reaginic group, tissue eosinophilia was found in 86.7% children and peripheral blood eosinophilia in 65.7%. In the nonreaginic group, the respective values were 18.6% and 20.9%. The difference between the two groups is statistically significant at p << 0.001. None of the children from the nonreaginic group was found to have outstandingly high peripheral and/or blood eosinophilia. The results show that determination of tissue and peripheral blood eosinophilia helps in arough assessment of asthma etiology.