title: Bet v 1, the major birch pollen allergen, initiates sensitization to Api g 1, the major allergen in celery: evidence at the T cell level.
abstract: Due to IgE cross-reactivity, birch pollen-allergic individuals frequently develop type I hypersensitivity reactions to celery tuber. We evaluated the T cell response to the major allergen in celeriac, Api g 1, and the cellular cross-reactivity with its homologous major allergen in birch pollen, Bet v 1. Api g 1-specific T cell lines (TCL) and clones (TCC) were established from peripheral blood mononuclear cells of allergic patients. Epitope mapping of Api g 1 with overlapping Api g 1-derived peptides revealed one dominant T cell-activating region, Api g 1(109-126). TCL and TCC generated with Api g 1 cross-reacted with the birch pollen allergen and, although initially stimulated with the food allergen, cellular responses to Bet v 1 were stronger than to Api g 1. Epitope mapping with Bet v 1-derived peptides revealed that T cells specific for several distinct epitopes distributed over the complete Bet v 1 molecule could be activated by Api g 1. Bet v 1(109-126) was identified as the most important T cell epitope for cross-reactivity with Api g 1. This epitope shares 72% amino acid sequence similarity with the major T cell-activating region of the food allergen, Api g 1(109-126). Our data provide evidence that humoral as well as cellular reactivity to the major celery allergen is predominantly based on cross-reactivity with the major birch pollen allergen. The activation of Bet v 1-specific Th2 cells by Api g 1, in particular outside the pollen season, may have consequences for birch pollen-allergic individuals.
authors.affiliation: Department of Pathophysiology, Division of Immunopathology, University of Vienna, Vienna, Austria. barbara.bohle@akh-wien.ac.at
authors.forename: Barbara
authors.initials: B
authors.lastname: Bohle
authors.forename: Astrid
authors.initials: A
authors.lastname: Radakovics
authors.forename: Beatrice
authors.initials: B
authors.lastname: Jahn-Schmid
authors.forename: Karin
authors.initials: K
authors.lastname: Hoffmann-Sommergruber
authors.forename: Gottfried F
authors.initials: GF
authors.lastname: Fischer
authors.forename: Christof
authors.initials: C
authors.lastname: Ebner
mesh_terms: D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D002460:Cell Line; D003429:Cross Reactions; D018984:Epitopes, T-Lymphocyte; D005512:Food Hypersensitivity / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000276:immunology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D010940:Plant Proteins / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000485:Allergens; D052179:Antigens, Plant; C096695:Api g 1 protein, Apium graveolens; D018984:Epitopes, T-Lymphocyte; D010446:Peptide Fragments; D010940:Plant Proteins; C061312:Bet v 1 allergen, Betula; D007073:Immunoglobulin E