Density of eosinophils reflects activity of disease in allergic asthmatic children.

Background: Low density eosinophils are more prominent in asthmatic patients compared with healthy subjects. LDE are metabolically more active and produce more tissue-injuring and spasmogenic proteins than normal eosinophils.

Objective And Methods: With a method providing information about eosinophils of 12 different densities we were able to study eosinophil density characteristics in 24 young patients in detail with allergic asthma in a stable phase, and in 21 patients after a bronchial allergen challenge.

Results: Study of the eosinophil density profile of patients and healthy controls revealed two density populations. Patients had more low density eosinophils than controls. In the patients eosinophil density characteristics and in particular the number of low density eosinophils correlated strongly with both FEV1% predicted (p = -0.66, P < 0.001) and FEV1/FVC (p = -0.47, P < 0.01) as well as with bronchial responsiveness to histamine (p = -0.68, P < 0.001) and house dust mite (p = -0.37, P < 0.05). Allergen induced bronchial reactions were associated with an increase in the number (P < 0.001) and percentage (P < 0.05) of low density eosinophils. A selective rise in the number of eosinophils collected from fractions with a low density accounted for the observed rise in the total number of eosinophils. Density changes did not differ between patients with an isolated early reaction and patients with both an early and a late reaction, nor was there a relation between the severity of the late reaction and the shift in eosinophil density.

Conclusion: In conclusion, peripheral blood eosinophil density characteristics and in particular numbers of low density eosinophils are closely related with indicators of the asthma severity under stable conditions. Allergen inhalation induces a further shift towards lower density suggesting additional activation of the eosinophils.