title: Increased expression levels of integrin α9β1 and CD11b on circulating neutrophils and elevated serum IL-17A in elderly aspiration pneumonia.
abstract: BACKGROUND
  Repeated aspiration pneumonia is a serious problem in the elderly. In aspiration pneumonia, neutrophils play an important role in acute lung injury, while CD18-independent neutrophil transmigration pathways have also been reported in acid-aspiration pneumonia animal models. However, the involvement of IL-17A and β1 integrin still remains unclear. The β1 integrin subfamily integrin α9β1 has been shown to be expressed on human neutrophils and to mediate adhesion to extracellular matrix proteins including the vascular cell adhesion molecule-1.
  
  
  OBJECTIVE
  To elucidate the possible involvement of β1 integrin subfamily and IL-17A in aspiration pneumonia.
  
  
  METHODS
  We analyzed the expression levels of CD11b, CD18 and integrin α9β1 in circulating neutrophils and serum concentration of IL-17A, IL-22 and IL-23 in elderly aspiration pneumonia patients (n = 32, 14 males and 18 females, 78.8 ± 3.9 years old) at 2 time points (on the day of admission before starting antibiotics and the day after finishing antibiotics) and compared the results with those of a control group (n = 30, 13 males and 17 females, 76.1 ± 3.4 years old).
  
  
  RESULTS
  Recombinant IL-17A stimulated integrin α9β1 and CD11b expression levels in healthy human neutrophils in vitro. The expression levels of integrin α9β1 and CD11b in circulating neutrophils were significantly higher in pneumonia patients compared with the controls. In addition, serum IL-17A concentration was significantly increased in pneumonia patients. Integrin α9β1 levels positively correlated with serum IL-17A and CD18 expression levels.
  
  
  CONCLUSIONS
  These findings suggest a potential role of integrin α9β1 expressed in neutrophils and elevated serum IL-17A in extravasation of neutrophils in cases of aspiration pneumonia.
authors.affiliation: Division of Medical Oncology and Respiratory Medicine, Department of Internal Medicine, Faculty of Medicine, Shimane University, Izumo, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Taooka
authors.forename: Miki
authors.initials: M
authors.lastname: Ohe
authors.forename: Lijun
authors.initials: L
authors.lastname: Chen
authors.forename: Akihisa
authors.initials: A
authors.lastname: Sutani
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Higashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Isobe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D039481:CD11b Antigen / Q000096:biosynthesis / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016023:Integrins / Q000096:biosynthesis / Q000378:metabolism*; D020381:Interleukin-17 / Q000096:biosynthesis / Q000097:blood*; D008297:Male; D009504:Neutrophils / Q000378:metabolism*; D011015:Pneumonia, Aspiration / Q000097:blood* / Q000276:immunology
chemical_list: D039481:CD11b Antigen; C508717:IL17A protein, human; C509295:ITGAM protein, human; D016023:Integrins; D020381:Interleukin-17; C113256:integrin alpha 9 beta 1