title: Increased platelet binding to circulating monocytes in idiopathic pulmonary fibrosis.
abstract: OBJECTIVE
  Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial pneumonia and its prognosis is poor. Epidemiological evidence suggests an association of IPF with vascular disease and thrombotic tendency, which may be related to platelet activation.
  
  
  METHODS
  Platelet-monocyte adhesion in peripheral blood was examined by flow cytometry in patients with IPF (n = 19), interstitial lung disease (ILD) other than IPF (n = 9), and control subjects without pulmonary fibrosis (n = 14). Expression of platelet activation markers P-selectin (CD62P), PSGL-1 (CD162), and CD40 ligand (CD40L) on leukocytes and platelets were studied. Plasma concentrations of soluble P-selectin and CD40L were measured by ELISA.
  
  
  RESULTS
  Significantly elevated levels of platelet-monocyte binding were found in patients with IPF (35.6 ± 4.34 % [mean ± SEM]) compared with patients with non-IPF ILD (23.5 ± 3.68 %) and non-ILD control subjects (16.5 ± 2.26 %; P < 0.01). There was a trend towards increased divalent cation-independent platelet-monocyte binding in IPF (6.0 ± 0.77 % [mean ± SEM]) compared with non-IPF ILD (4.3 ± 1.38 %) and control subjects without ILD (3.1 ± 1.75 %; P = 0.058). There was no differential surface expression of platelet activation markers on subsets of leukocytes or platelets. Plasma concentrations of CD40L and soluble P-selectin did not differ between IPF and control subjects. Platelet-monocyte binding had no significant correlation with percent predicted TLco or FVC.
  
  
  CONCLUSIONS
  Platelet-monocyte binding is increased in IPF, suggesting increased platelet activation. This conjugation is predominantly calcium-dependent, but there may be more calcium-independent adhesion in IPF. These findings support further research into the role of platelet activation in IPF.
authors.affiliation: Division of Cardiovascular and Respiratory Studies, Castle Hill Hospital, Castle Road, Cottingham, HU16 5JQ, UK, ahmedfahim@doctors.org.uk.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Fahim
authors.forename: Michael G
authors.initials: MG
authors.lastname: Crooks
authors.forename: Alyn H
authors.initials: AH
authors.lastname: Morice
authors.forename: Simon P
authors.initials: SP
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D016022:Case-Control Studies; D015815:Cell Adhesion Molecules / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000097:blood* / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism*; D010973:Platelet Adhesiveness; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D015815:Cell Adhesion Molecules; D002118:Calcium