Abnormal expression of neutrophil elastase in neutrophils of SCN patients during treatment with G-CSF. (A) Immunofluorescence staining of NE in circulating neutrophils from SCN patients. Polymorphonuclear lymphocytes (PMNs) were obtained from peripheral blood, cytocentrifugated, and stained with anti-NE antibody; nuclei were counterstained with DAPI. The majority of cells from a control subject (CTR) show a strong cytoplasmatic expression of NE, whereas NE is detectable in a minority of cells obtained from patients 1, 2, and 3. Experiment shown is representative of 2 performed. (B) Cell lysates of neutrophils purified from 3 patients (P1, P2, and P3), 2 healthy control subjects (C1, C2), and 2 idiopathic neutropenia patients (C3 and C4) were subjected to Western blot analysis with anti–neutrophil elastase antibody. β-Actin was used to normalize protein levels. The 29- and 32-kDa polypeptides are indicated by arrows. The band indicated by a dot could correspond to the previously identified elastase-alpha1 antitrypsin complex.²¹