Eosinophil cationic protein is not only a distinctive eosinophil protein

We read with interest the article by Qiu et al (Thorax 2007;62:475–82). In this paper, neutrophils and eosinophils were identified using mouse anti-human neutrophil elastase and anti-eosinophil cationic protein (ECP), both monoclonal antibodies (mAbs). mAbs against ECP have been used to detect total eosinophils, but immunostaining techniques evidenced that the number of ECP+ cells was higher than the number of eosinophils.1 Recent studies show that ECP is not only a distinctive eosinophil protein, but has been found in neutrophils.1–3

This work was supported by grants from the Junta de Andalucia (Ayudas Grupos de Investigación), Fundación de la Sociedad Española de Alergia e Inmunología Clínica, Fundación Sanitaria Virgen Macarena and Fundación Alergol, Spain. AV was supported by fellowships from the Ministerio de Ciencia y Tecnología, and Fundación Alergol. JM is under the Programa de Intensificación de la Actividad Investigadora del Sistema Nacional de Salud.