Eosinophil cationic protein (ECP) and eosinophil protein X (EPX) concentrations in serum and bronchial lavage fluid in asthma. Effect of prednisolone treatment.

Background: Eosinophil granule proteins may contribute to bronchial hyperresponsiveness in asthma.

Objective: To measure eosinophil cationic protein (ECP) and eosinophil protein X (EPX) in serum and bronchial lavage fluid from 20 asthmatics and 16 control subjects. To assess the effect on these eosinophil proteins of corticosteroid treatment of asthma. To determine whether serum ECP and EPX measured weekly in a longitudinal study for 10 weeks reflected changes in lung function.

Methods: Eosinophil granule proteins were measured by radioimmunoassay of bronchial wash (BW), bronchoalveolar lavage (BAL) and serum.

Results: Eosinophils were elevated in BAL (P < 0.01), BW (P < 0.01) and blood (P < 0.01) from asthmatics compared with control subjects. Eosinophils cationic protein concentration was significantly elevated in BAL (P < 0.05) and BW from asthmatics (P < 0.01) and EPX was increased in BAL (P < 0.05) and BW (P < 0.01). These changes were also reflected in elevated serum ECP (P < 0.01) and EPX (P < 0.01) concentrations in asthmatic subjects. There was no significant difference between subjects receiving prednisolone and the placebo group, but there was a fall in ECP in BW (P < 0.05) and serum (P < 0.01) and in EPX in BW (P < 0.01) and serum (P < 0.01) within the group receiving prednisolone. In the longitudinal study there was only a significant difference between ECP values associated with highest and lowest peak expiratory flow rate (PEFR) (P < 0.05).

Conclusions: These data confirm a role for eosinophil activation in the airway in asthma pathogenesis, and add some support to the hypothesis that corticosteroids may inhibit eosinophil activation in asthma.