title: Sequential allergen desensitization of basophils is non-specific and may involve p38 MAPK.
abstract: BACKGROUND
  Sequential allergen desensitization provides temporary tolerance for allergic patients. We adapted a clinical protocol to desensitize human blood basophils ex vivo and investigated the mechanism and allergen specificity.
  
  
  METHODS
  We included 28 adult, grass allergic subjects. The optimal, activating allergen concentration was determined by measuring activated CD63(+) CD193(+) SS(Low) basophils in a basophil activation test with 8 log-dilutions of grass allergen. Basophils in whole blood were desensitized by incubation with twofold to 2.5-fold increasing allergen doses in 10 steps starting at 1 : 1000 of the optimal dose. Involvement of p38 mitogen-activated protein kinase (MAPK) was assessed after 3 min of allergen stimulation (n = 7). Allergen specificity was investigated by desensitizing cells from multi-allergic subjects with grass allergen and challenging with optimal doses of grass, birch, recombinant house dust mite (rDer p2) allergen or anti-IgE (n = 10).
  
  
  RESULTS
  Desensitization reduced the fraction of blood basophils responding to challenge with an optimal allergen dose from a median (IQR) 81.0% (66.3-88.8) to 35.4% (19.8-47.1, P < 0.0001). CD63 MFI expression was reduced from 68 248 (29 336-92 001) to 30 496 (14 046-46 179, P < 0.0001). Basophils from multi-allergic subjects were desensitized with grass allergen. Challenge with grass allergen resulted in 39.6% activation (15.8-58.3). An unrelated challenge (birch, rDer p2 or anti-IgE) resulted in 53.4% activation (30.8-66.8, P = 0.16 compared with grass). Desensitization reduced p38 MAPK phosphorylation from a median 48.1% (15.6-92.8) to 26.1% (7.4-71.2, P = 0.047) and correlated with decrease in CD63 upregulation (n = 7, r > 0.79, P < 0.05).
  
  
  CONCLUSIONS
  Desensitization attenuated basophil response rapidly and non-specifically at a stage before p38 MAPK phosphorylation.
authors.affiliation: Department of Pulmonary Medicine and Allergy, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: S K
authors.initials: SK
authors.lastname: Witting Christensen
authors.forename: I
authors.initials: I
authors.lastname: Kortekaas Krohn
authors.forename: J
authors.initials: J
authors.lastname: Thuraiaiyah
authors.forename: T
authors.initials: T
authors.lastname: Skjold
authors.forename: J M
authors.initials: JM
authors.lastname: Schmid
authors.forename: H J H
authors.initials: HJ
authors.lastname: Hoffmann
mesh_terms: D000328:Adult; D015549:Basophil Degranulation Test; D001491:Basophils / Q000276:immunology*; D003888:Desensitization, Immunologic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D006109:Poaceae / Q000276:immunology; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology*; D055815:Young Adult; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology*
chemical_list: D048051:p38 Mitogen-Activated Protein Kinases
keywords: allergen desensitization; basophil activation test; basophil granulocytes; basophil sensitivity; p38 MAPK