title: Alveolar mast cells shift to an FcεRI-expressing phenotype in mild atopic asthma: a novel feature in allergic asthma pathology.
abstract: BACKGROUND
  A unique feature of alveolar mast cells is their low high-affinity IgE receptor (FcεRI) expression. Recent discoveries in uncontrolled asthma suggest that the appearance of FcεRI-expressing alveolar mast cells may be a novel disease-specific feature of allergic asthma. This study investigates whether increased FcεRI-expressing alveolar mast cells are present in patients with mild allergic asthma or even in non-asthmatic allergic rhinitis patients (AR) who have developed bronchial hyperactivity (BHR).
  
  
  METHODS
  Bronchial and alveolar tissues were obtained from healthy controls, AR patients with or without BHR, and AR patients with concurrent asthma. Samples were processed for immunohistochemical identification of MC(T) and MC(TC) and expression of FcεRI and surface-bound IgE.
  
  
  RESULTS
  Bronchial mast cell expression of FcεRI was high in all groups. In contrast, in the alveolar tissue, the expression of FcεRI on mast cells was low in healthy controls and in the AR patient groups, whereas a high expression was present in AR patients with concurrent asthma (P = 0.006 compared to controls). The asthmatics had a 29-fold increase in numbers (P = 0.006) and a 19-fold increase in proportion (P = 0.007) of alveolar mast cells that expressed surface-bound IgE.
  
  
  CONCLUSIONS
  The present data show that alveolar mast cells in patients with mild atopic asthma, but not atopic patients with AR, have turned into a highly FcεRI- and IgE-expressing phenotype. These data support the hypothesis that increased FcεRI expression on alveolar mast cells is a novel disease-specific feature of allergic asthma that is important for understanding asthma phenotypes and designing new therapeutic strategies.
authors.affiliation: Department of Respiratory Medicine and Allergology, Lund University, Lund, Sweden.
authors.forename: C K
authors.initials: CK
authors.lastname: Andersson
authors.forename: E
authors.initials: E
authors.lastname: Tufvesson
authors.forename: D
authors.initials: D
authors.lastname: Aronsson
authors.forename: A
authors.initials: A
authors.lastname: Bergqvist
authors.forename: M
authors.initials: M
authors.lastname: Mori
authors.forename: L
authors.initials: L
authors.lastname: Bjermer
authors.forename: J S
authors.initials: JS
authors.lastname: Erjefält
mesh_terms: D000328:Adult; D001249:Asthma / Q000276:immunology*; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000276:immunology*; D008875:Middle Aged; D010641:Phenotype; D011650:Pulmonary Alveoli / Q000276:immunology*; D017455:Receptors, IgE / Q000378:metabolism*; D055815:Young Adult
chemical_list: D017455:Receptors, IgE; D007073:Immunoglobulin E