title: Bet v 1, the major birch pollen allergen, and Mal d 1, the major apple allergen, cross-react at the level of allergen-specific T helper cells.
abstract: BACKGROUND
  Food allergy to apple is frequent in individuals allergic to tree pollen. The major allergens of birch, Bet v 1, and apple, Mal d 1, have been cloned and sequenced and display a high degree of sequence identity, leading to IgE cross-reactivity.
  
  
  OBJECTIVE
  We sought to investigate cross-reactivity between Bet v 1 and Mal d 1 at the level of allergen-specific T lymphocytes.
  
  
  METHODS
  PBMCs of 13 patients allergic to birch pollen with oral allergy syndrome to apple were stimulated with rBet v 1 and rMal d 1, respectively, thereby establishing allergen-specific T-cell lines and T-cell clones. rMal d 1-specific T-cell cultures were tested for reactivity with rBet v 1, and rBet v 1-specific T cells were analyzed for reactivity with apple allergen. Cytokine production patterns in response to specific stimulation were evaluated. A selection of cross-reacting T-cell clones was mapped for epitope specificity by the use of overlapping Bet v 1- derived peptides.
  
  
  RESULTS
  Nineteen Mal d 1-specific T-cell clones were produced, 79% of which cross-reacted with Bet v 1. Eight of 18 Bet v 1-specific T-cell clones cross-reacted with Mal d 1. Six peptides representing cross-reactive T-cell epitopes could be identified. The respective fragments from birch and apple displayed approximately 50% amino acid identity. Seventy percent of the cross-reactive T-cell clones revealed a T(H2)-like cytokine production pattern.
  
  
  CONCLUSIONS
  The results indicate that cross-reactivity between apple and birch pollen leading to the clinical oral allergy syndrome occurs not only at the serologic, but also at the cellular level.
authors.affiliation: Institute of General and Experimental Pathology, Department of Immunopathology, University of Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Fritsch
authors.forename: B
authors.initials: B
authors.lastname: Bohle
authors.forename: U
authors.initials: U
authors.lastname: Vollmann
authors.forename: U
authors.initials: U
authors.lastname: Wiedermann
authors.forename: B
authors.initials: B
authors.lastname: Jahn-Schmid
authors.forename: M
authors.initials: M
authors.lastname: Krebitz
authors.forename: H
authors.initials: H
authors.lastname: Breiteneder
authors.forename: D
authors.initials: D
authors.lastname: Kraft
authors.forename: C
authors.initials: C
authors.lastname: Ebner
mesh_terms: D000328:Adult; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D003429:Cross Reactions; D016207:Cytokines / Q000096:biosynthesis; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000276:immunology*; D019685:Rosales; D012882:Skin Tests; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D014197:Trees
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; C095551:MALD1 protein, Malus domestica; D010940:Plant Proteins; C061312:Bet v 1 allergen, Betula