Eosinophil cationic protein relates to sputum neutrophil counts in healthy subjects

Abstract

Eosinophil cationic protein (ECP) has been regarded as an eosinophil-specific protein. Sputum ECP levels have been shown to be elevated (median [interquartile range (IQR)], 1040 [3008] μg/L) in stable asthmatic subjects with sputum eosinophilia (median [IQR], 5.2% [19.4%] eosinophils).1 However, it has recently been shown that proteins immunochemically indistinguishable from ECP are also present in peripheral blood neutrophils.2 High levels of sputum ECP have also been observed in subjects without associated sputum eosinophilia.