title: Human blood basophils do not act as antigen-presenting cells for the major birch pollen allergen Bet v 1.
abstract: BACKGROUND
  Several studies in mice have recently shown that basophils can act as antigen-presenting cells (APC) inducing Th2-mediated immune responses against parasites or protease allergens. The aim of this study was to investigate whether human basophils function as APC for the major birch pollen allergen Bet v 1.
  
  
  METHODS
  Fluorescently labeled Bet v 1 was used to assess surface binding and internalization of allergen by basophils and different types of APC from birch pollen-allergic and nonallergic individuals. Sorted basophils were analyzed in terms of up-regulation of MHC class II and co-stimulatory molecules in the absence and presence of IL-3 and IFN-γ by flow cytometry. Expression of proteins crucial for antigen presentation, namely cathepsin S and invariant chain, was determined. Basophils were used as APC in co-culture experiments with Bet v 1-specific T-cell clones (TCCs).
  
  
  RESULTS
  Basophils from birch pollen-allergic donors very efficiently bound Bet v 1 through IgE/FcεRI complexes on their surface. In contrast to professional APC, basophils did not internalize allergen and expressed marginal levels of cathepsin S and invariant chain. HLA-DP, HLA-DQ, CD80/CD86, and CD40 were absent from purified basophils even when stimulated with IL-3 plus IFN-γ. IL-3/IFN-γ marginally up-regulated HLA-DR. Bet v 1-pulsed basophils failed to induce proliferative and cytokine responses in Bet v 1-specific, HLA-DR-restricted TCCs.
  
  
  CONCLUSIONS
  Human basophils neither internalize, process nor present Bet v 1. Because Bet v 1 is a highly relevant allergen, we conclude that basophils play no role as APC in IgE-mediated allergy in humans.
authors.affiliation: Christian Doppler Laboratory for Immunomodulation, Medical University of Vienna, Vienna, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Kitzmüller
authors.forename: B
authors.initials: B
authors.lastname: Nagl
authors.forename: S
authors.initials: S
authors.lastname: Deifl
authors.forename: C
authors.initials: C
authors.lastname: Walterskirchen
authors.forename: B
authors.initials: B
authors.lastname: Jahn-Schmid
authors.forename: G J
authors.initials: GJ
authors.lastname: Zlabinger
authors.forename: B
authors.initials: B
authors.lastname: Bohle
mesh_terms: D000485:Allergens / Q000276:immunology*; D000938:Antigen-Presenting Cells / Q000276:immunology*; D052179:Antigens, Plant / Q000276:immunology* / Q000378:metabolism; D001491:Basophils / Q000276:immunology* / Q000378:metabolism; D004705:Endocytosis / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology / Q000378:metabolism; D011058:Pollen / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D017455:Receptors, IgE / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D017455:Receptors, IgE; C061312:Bet v 1 allergen, Betula