title: Activated platelets are the source of elevated levels of soluble CD40 ligand in the circulation of inflammatory bowel disease patients.
abstract: BACKGROUND
  The CD40/CD40L system, a key regulator and amplifier of immune reactivity, is activated in inflammatory bowel disease (IBD) mucosa.
  
  
  OBJECTIVE
  To determine whether plasma levels of sCD40L are elevated in Crohn's disease (CD) and ulcerative colitis (UC) patients compared with normal controls, to investigate the cellular source of sCD40L, and to explore CD40L induction mechanisms.
  
  
  METHODS
  CD, UC, and normal control subjects were studied.
  
  
  METHODS
  The concentration of sCD40L in plasma and supernatants of freshly isolated platelets and autologous peripheral blood T cells (PBT) was measured by ELISA. Surface CD40L expression level was measured by flow cytometry in resting and thrombin activated platelets, and unstimulated and CD3/CD28 stimulated PBT before and after coculture with human intestinal microvascular endothelial cells (HIMEC).
  
  
  RESULTS
  Compared with normal controls, plasma sCD40L levels were significantly higher in both CD and UC patients and proportional to the extent of mucosal inflammation. Platelets from IBD patients displayed a significantly higher surface CD40L expression than those from control subjects, and released greater amounts of sCD40L than autologous PBT. Contact with IL-1beta activated HIMEC induced significant upregulation of CD40L surface expression and release by platelets.
  
  
  CONCLUSIONS
  Elevated levels of sCD40L in the circulation of IBD patients reflect enhanced surface expression and release of CD40L by platelets. This phenomenon translates to an increased platelet activation state apparently induced by passage through an inflamed mucosal microvascular bed, a conclusion supported by the positive correlation of plasma sCD40L levels with the extent of anatomical involvement by IBD. These results suggest that platelet-endothelial interactions critically contribute to activation of the CD40 pathway in IBD.
authors.affiliation: Division of Gastroenterology, University Hospitals of Cleveland, Case Western Reserve University School of Medicine Cleveland, Ohio 44106-4952, USA.
authors.forename: S
authors.initials: S
authors.lastname: Danese
authors.forename: J A
authors.initials: JA
authors.lastname: Katz
authors.forename: S
authors.initials: S
authors.lastname: Saibeni
authors.forename: A
authors.initials: A
authors.lastname: Papa
authors.forename: A
authors.initials: A
authors.lastname: Gasbarrini
authors.forename: M
authors.initials: M
authors.lastname: Vecchi
authors.forename: C
authors.initials: C
authors.lastname: Fiocchi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001792:Blood Platelets / Q000737:chemistry; D015153:Blotting, Western / Q000379:methods; D023201:CD40 Ligand / Q000032:analysis / Q000097:blood*; D016022:Case-Control Studies; D018920:Coculture Techniques; D003093:Colitis, Ulcerative / Q000097:blood* / Q000276:immunology; D003424:Crohn Disease / Q000097:blood* / Q000276:immunology; D042783:Endothelial Cells / Q000737:chemistry; D004730:Endothelium, Vascular / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000097:blood / Q000276:immunology; D007375:Interleukin-1 / Q000494:pharmacology; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D015539:Platelet Activation; D018709:Statistics, Nonparametric; D013601:T-Lymphocytes / Q000737:chemistry; D013917:Thrombin / Q000494:pharmacology
chemical_list: D007375:Interleukin-1; D023201:CD40 Ligand; D013917:Thrombin