title: Characterization of the T-cell response to Dau c 1, the Bet v 1-homolog in carrot.
abstract: BACKGROUND
  In contrast to other Bet v 1-related food allergens, the major carrot allergen, Dau c 1, has been suggested to induce food allergy independently from Bet v 1. As T cells are crucial in the sensitization process, we sought to characterize the T-cell response to Dau c 1 and its cross-reactivity with Bet v 1.
  
  
  METHODS
  Dau c 1-specific T-cell lines (TCL) and clones (TCC) established from PBMC of birch pollen-allergic patients with carrot allergy were analyzed for reactivity to Bet v 1, epitope specificity, allergen-induced cytokine secretion, and expression of integrins α4β7 and α4β1, critical for gut and lung homing, respectively. mRNA expression of GATA3 and Tbet was analyzed in sorted CD3+CD4+CFSElowcells proliferating upon stimulation of PBMC with Dau c 1 or Bet v 1. Dau c 1 was incubated with endolysosomal proteases, and the resulting fragments were identified by mass spectrometry.
  
  
  RESULTS
  Among 14 distinct T-cell-activating regions, Dau c 1139-153was recognized by 55% of the patients. Only 6 of 15 (40%) Dau c 1-specific TCL and 9 of 21 (43%) TCC reacted with Bet v 1. Bet v 1-nonreactive TCC were mainly Th1-like and showed a higher expression of the integrin β7 and a significantly lower expression of the integrin β1 than Bet v 1-positive TCC. A Th1-like response was also detected in Dau c 1-reactive CD3+CD4+CFSElowcells. Full-length Dau c 1 was still detectable after 48 h of endolysosomal degradation. Proteolytic fragments of Dau c 1 matched its T-cell-activating regions.
  
  
  CONCLUSIONS
  Dau c 1 displays several characteristics of sensitizing allergens, namely a major T-cell-activating region, low susceptibility to endolysosomal degradation, and induction of a Bet v 1-independent T-cell response. These cellular insights confirm that the major carrot allergen has a special status among Bet v 1-related food allergens.
authors.affiliation: Department of Pathophysiology and Allergy Research and Christian Doppler Laboratory for Immunomodulation, Medical University of Vienna, Vienna, Austria.
authors.forename: N
authors.initials: N
authors.lastname: Zulehner
authors.affiliation: Department of Pathophysiology and Allergy Research and Christian Doppler Laboratory for Immunomodulation, Medical University of Vienna, Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Nagl
authors.affiliation: Department of Molecular Biology, University of Salzburg, Salzburg, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Briza
authors.affiliation: Department of Molecular Biology, University of Salzburg, Salzburg, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Roulias
authors.affiliation: Allergy Unit, Department of Dermatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Ballmer-Weber
authors.affiliation: Institute of Immunology, Medical University of Vienna, Vienna, Austria.
authors.forename: G J
authors.initials: GJ
authors.lastname: Zlabinger
authors.affiliation: Department of Molecular Biology, University of Salzburg, Salzburg, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Ferreira
authors.affiliation: Department of Pathophysiology and Allergy Research and Christian Doppler Laboratory for Immunomodulation, Medical University of Vienna, Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Bohle
mesh_terms: D000485:Allergens / Q000276:immunology*; D000918:Antibody Specificity / Q000276:immunology; D052179:Antigens, Plant / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology; D018552:Daucus carota / Q000276:immunology*; D011992:Endosomes / Q000378:metabolism; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005512:Food Hypersensitivity / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D008247:Lysosomes / Q000378:metabolism; D010940:Plant Proteins / Q000276:immunology*; D037182:T-Cell Antigen Receptor Specificity / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D000485:Allergens; D052179:Antigens, Plant; C119925:Dau c 1 protein, Daucus carota; D018984:Epitopes, T-Lymphocyte; D010940:Plant Proteins; D007073:Immunoglobulin E
keywords: Bet v 1; Dau c 1; T cells; allergic sensitization; birch pollen-associated food allergy