title: Intracellular expression and serum levels of eosinophil peroxidase (EPO) and eosinophil cationic protein in asthmatic children.
abstract: BACKGROUND
  Eosinophils are involved in the chronic inflammatory response in asthma and their basic proteins are thought to play a major pathophysiological role in this process. While serum levels of basic proteins have been used to monitor the ongoing allergic disease, little is known about the intracellular expression of these proteins in clinical situations.
  
  
  OBJECTIVE
  The aim of the study was to determine the intracellular expression of eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO) in asthmatic children and control subjects and relate it to serum levels of both proteins, lung function tests and immunoglobulin (Ig)E levels.
  
  
  METHODS
  Serum ECP and EPO concentrations were determined by immunoassays in 13 asthmatic children (mean age: 9 +/- 1 years, mean FEV1: 92 +/- 10% predicted, geometric mean PC20 histamine 0.5 mg/mL) and 10 age-matched, healthy control subjects. A flow cytometric single cell assay was employed to detect intracellular ECP and EPO in peripheral blood eosinophils.
  
  
  RESULTS
  While serum concentrations of both ECP (asthma: median 15.0 microg/L [range 3.6-57.7] vs control: 5.9 microg/L [2.7-9.1]; P = 0.02) and EPO (22.9 microg/L [5.2-82.5] vs 7. 2 microg/L [2.5-12.7]; P = 0.008) were significantly elevated in asthmatics, the intracellular expression of ECP and EPO (measured as mean fluorescence intensity) was decreased (EG1: 55.3 [17.7-120.8] vs 100.3 [46.5-264.4]; P = 0.01; EG2: 80.2 [24.1-135.3] vs 133.7 [32. 1-244.9]; P = 0.04 and EPO: 49.7 [23.1-155.8] vs 94.9 [28.8-115.2]; P = 0.03). In asthmatics there was a significant correlation of FEV1 with intracellular ECP and of bronchial hyperresponsiveness with serum EPO and ECP. Furthermore, total IgE levels were positively correlated with serum EPO only.
  
  
  CONCLUSIONS
  We conclude that in asthmatics the intracellular content of ECP and EPO in peripheral eosinophils is reduced possibly due to degranulation. Epitope masking in activated eosinophils or a shift to early bone marrow-derived progenitors with less granule proteins are further possible explanations.
authors.affiliation: Department of Respiratory Medicine, Hannover Medical School, Hannover, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Krug
authors.forename: U
authors.initials: U
authors.lastname: Napp
authors.forename: I
authors.initials: I
authors.lastname: Enander
authors.forename: E
authors.initials: E
authors.lastname: Eklund
authors.forename: C H
authors.initials: CH
authors.lastname: Rieger
authors.forename: U
authors.initials: U
authors.lastname: Schauer
mesh_terms: D001249:Asthma / Q000097:blood* / Q000276:immunology; D001798:Blood Proteins / Q000378:metabolism*; D002648:Child; D047091:Eosinophil Granule Proteins; D047209:Eosinophil Peroxidase; D004804:Eosinophils / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D008297:Male; D010544:Peroxidases / Q000378:metabolism*; D012129:Respiratory Function Tests; D012260:Ribonucleases
chemical_list: D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D007073:Immunoglobulin E; D047209:Eosinophil Peroxidase; D010544:Peroxidases; D012260:Ribonucleases