title: Clinical implications of correlation between peripheral eosinophil count and serum levels of IL-5 and tryptase in acute eosinophilic pneumonia.
abstract: BACKGROUND
  The peripheral eosinophil count (PEC) tends to increase during the course of acute eosinophilic pneumonia (AEP), and an initially elevated PEC is associated with milder disease. However, there is a lack of data regarding these phenomena and inflammatory process of AEP.
  
  
  METHODS
  We prospectively evaluated serial changes in serum interleukin (IL)-5 levels and the correlation between the initial level of IL-5 and the PEC to investigate whether the initial PEC indicates a resolving state of inflammation. We also evaluated serum tryptase levels to investigate the possibility of involvement of mast cell activity in AEP.
  
  
  RESULTS
  Twenty-one AEP patients were included, and all patients improved within 10 days after corticosteroid treatment. The median initial serum IL-5 level among all patients was 561.0 pg/mL, which decreased to zero at 10 days of follow-up (n = 15, P < 0.001). The median initial serum tryptase level (detectable in 20 of 21 patients) was 3.7 ng/mL and decreased to a median of 1.1 ng/mL at 10 days of follow-up (n = 15, P < 0.001). The initial serum IL-5 and C-reactive protein levels were positively correlated (P = 0.009, r = 0.556), and the initial serum IL-5 level was inversely correlated with the initial PEC (P = 0.004, r = -0.603).
  
  
  CONCLUSIONS
  Our data suggest that IL-5 is an important cytokine involved in the recruitment of eosinophils from peripheral blood into the lungs, that an initially elevated PEC is associated with a resolving state of inflammation, and that mast cells are potentially involved in the inflammatory process of AEP.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Armed Forces Capital Hospital, Seong-nam, Gyeonggi Province, Republic of Korea. Electronic address: byungwoo.jhun@gmail.com.
authors.forename: Byung Woo
authors.initials: BW
authors.lastname: Jhun
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Armed Forces Capital Hospital, Seong-nam, Gyeonggi Province, Republic of Korea. Electronic address: chrisjinny@naver.com.
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Armed Forces Capital Hospital, Seong-nam, Gyeonggi Province, Republic of Korea. Electronic address: newtypex0317@gmail.com.
authors.forename: Kang
authors.initials: K
authors.lastname: Kim
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Armed Forces Capital Hospital, Seong-nam, Gyeonggi Province, Republic of Korea. Electronic address: leejieun77@gmail.com.
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, The Armed Forces Capital Hospital, Seong-nam, Gyeonggi Province, Republic of Korea. Electronic address: dududuck@hanmail.net.
authors.forename: Duck Jin
authors.initials: DJ
authors.lastname: Hong
mesh_terms: D000208:Acute Disease; D015415:Biomarkers / Q000097:blood; D001999:Bronchoscopy / Q000379:methods; D004804:Eosinophils / Q000473:pathology*; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D015848:Interleukin-5 / Q000097:blood*; D007958:Leukocyte Count; D008297:Male; D011446:Prospective Studies; D011657:Pulmonary Eosinophilia / Q000188:drug therapy / Q000276:immunology*; D053802:Tryptases / Q000097:blood*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D005938:Glucocorticoids; D018836:Inflammation Mediators; D015848:Interleukin-5; D053802:Tryptases
keywords: Acute eosinophilic pneumonia; Interleukin-5; Peripheral eosinophil count; Tryptase