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Eosinophil activation status and corticosteroid responsiveness in severe asthma
M Bossé1, M Audette, G Laflamme
1Unité de Recherche, Centre de Pneumologie de l'Hôpital Laval, Centre Hospitalier Universitaire de Québec, Université Laval, Ste-Foy, Québec, Canada.
Background:
Since eosinophils are implicated in asthma pathogenesis, we investigated whether these cells were activated in severe asthma.
Methods:
Twenty-six asthmatics with different clinical responses to oral corticosteroid (CS), i.e. sensitive [change in forced expiratory volume in 1 s (DeltaFEV(1)) >/= 25% after oral methylprednisolone, 40 mg daily, for 14 days, n = 7], resistant (DeltaFEV(1) /= 20 mg oral prednisone daily for acceptable asthma control, n = 10), were studied.
Results:
Calcium ionophore-induced leukotriene (LT) C(4) release of purified blood eosinophils was similar in the three groups. Cell incubation with granulocyte-macrophage colony-stimulating factor (GM-CSF) enhanced ionophore-induced LTC(4) release, and this effect was higher in CS-sensitive (5-fold) than in CS-resistant subjects (1.7-fold) (p = 0.02). CS treatment decreased blood eosinophil counts in these two groups of subjects (p
Conclusions:
Eosinophils from CS-dependent asthmatics have an impaired response to CS, whereas serum from CS-resistant subjects contains an inhibitor of eosinophil response to GM-CSF.