title: Expression of tissue factor by eosinophils in patients with chronic urticaria.
abstract: BACKGROUND
  Although several cases of chronic urticaria (CU) are currently regarded as autoimmune in origin, associated with histamine-releasing autoantibodies, an activation of blood coagulation via tissue factor (TF) and a strong expression of TF in lesional skin have been described. Eosinophils, which are involved in CU skin lesions, have recently been demonstrated as the major source of TF in human blood. We assessed whether eosinophils are the cellular source of TF in CU skin lesions.
  
  
  METHODS
  Twenty patients with severe CU were studied. Skin biopsy specimens were taken from wheals. The control group consisted of specimens of perilesional normal skin from different types of skin tumours (10) and various skin disorders with non-eosinophilic infiltrates, including leukocytoclastic vasculitis (7), lichen planus (8) and mastocytosis (3). TF expression was evaluated by immunohistochemical methods using an anti-TF monoclonal antibody. Co-localization of TF and eosinophil cationic protein, a classic cell marker of eosinophils, was investigated by double-staining studies using 2 specific monoclonal antibodies in the 4 specimens showing the highest TF reactivity scores.
  
  
  RESULTS
  All specimens from patients with CU clearly showed TF expression that was absent in all normal control specimens (p = 0.0001) and in the skin disorders with non-eosinophilic infiltrates (p = 0.001-0.0001). The double-staining experiments for TF and eosinophil cationic protein clearly showed that the TF-positive cells were eosinophils.
  
  
  CONCLUSIONS
  Eosinophils are the main source of TF in CU lesional skin. This finding highlights the role of these cells in the pathophysiology of CU and might pave the way for new therapeutic strategies.
authors.affiliation: Department of Internal Medicine,University of Milan, Milan, Italy. massimo.cugno@unimi.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Cugno
authors.forename: Angelo V
authors.initials: AV
authors.lastname: Marzano
authors.forename: Alberto
authors.initials: A
authors.lastname: Tedeschi
authors.forename: Daniele
authors.initials: D
authors.lastname: Fanoni
authors.forename: Luigia
authors.initials: L
authors.lastname: Venegoni
authors.forename: Riccardo
authors.initials: R
authors.lastname: Asero
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002908:Chronic Disease; D004804:Eosinophils / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013925:Thromboplastin / Q000378:metabolism*; D014581:Urticaria / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D013925:Thromboplastin