title: Mast cell number and phenotype in chronic idiopathic urticaria.
abstract: BACKGROUND
  Increased levels of histamine have been previously demonstrated in patients with chronic idiopathic urticaria.
  
  
  OBJECTIVE
  The purpose of the study was to determine whether increased numbers of mast cells are present in lesional skin from such patients.
  
  
  METHODS
  Mast cells have been quantified in lesional (n = 11) and nonlesional (n = 9) skin from patients with chronic idiopathic urticaria and compared with site-matched skin from healthy control subjects (n = 10). Mast cells were identified by using a sensitive, double-labeling immunohistochemical technique with specific monoclonal antibodies to mast cell tryptase and chymase and quantified under light microscopy.
  
  
  RESULTS
  No significant differences in mast cell numbers from lesional, nonlesional, or control skin were observed (p > 0.1, Student's t test). In both patients with urticaria and control subjects, more than 99% of cutaneous mast cells contained tryptase and chymase.
  
  
  CONCLUSIONS
  These data indicate that increased skin histamine in chronic idiopathic urticaria is not caused by increased mast cells and may alternatively reflect an increase in histamine content per mast cell, enhanced mast cell activation, or recruitment of basophils into skin in patients with chronic idiopathic urticaria.
authors.affiliation: Department of Allergy & Respiratory Medicine, United Medical School, Guy's Hospital, London, England.
authors.forename: C H
authors.initials: CH
authors.lastname: Smith
authors.forename: C
authors.initials: C
authors.lastname: Kepley
authors.forename: L B
authors.initials: LB
authors.lastname: Schwartz
authors.forename: T H
authors.initials: TH
authors.lastname: Lee
mesh_terms: D000328:Adult; D002452:Cell Count; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008407:Mast Cells / Q000473:pathology* / Q000502:physiology*; D008875:Middle Aged; D010641:Phenotype; D012016:Reference Values; D012867:Skin / Q000473:pathology; D014581:Urticaria / Q000473:pathology*