Celery allergens in patients with positive double-blind placebo-controlledfood challenge

Background: Recently, for the first time, allergy to celery was confirmed b y double-blind placebo-controlled food challenge (DBPCFC), Api g 1, Api g 4 , cross-reactive carbohydrate determinants (CCD), and a 60 kDa allergen hav e been described as celery allergens. Objective: To get insights in IgE responses of patients with a positive DBP CFC to celery tuber (celeriac) compared with patients with a negative chall enge test, Methods: Specific IgE to native and heated celery tuber and to recombinant Api g 1, the major celery allergen, were determined by enzyme allergosorben t test and immunoblotting, IgE binding to Api g 1, Api g 4, and CCD was con firmed by inhibition experiments that used recombinant Api g 1, recombinant Api g 4, pure N-glycans, and extracts of celeriac, lychee fruit, and polle ns of birch, mugwort, and timothy grass as inhibitors. Results: Immunoblotting with sera from 22 patients with a positive DBPCFC t o celeriac confirmed the presence of known allergenic structures: The major allergen Api g 1 (16 kDa) was recognized by IgE from 13 of 22 patients (59 %), Another major allergen was CCD, determined by IgE reactivity in 12 of 2 2 patients (55%), Celery profilin, Api g 4, was recognized by IgE from 5 of 22 patients (23%), Conclusion: Our DBPCFC-positive patients exclusively presented IgE to known celery allergens, although the prevalences were slightly different than we re previously reported. No obvious differences were found in patients with positive IgE antibody but negative challenge test, IgE binding to all 3 str uctures in celeriac extract was inhibited by birch pollen extract, whereas mugwort pollen extract could only inhibit IgE reactivity to Api g 4 and CCD , Inhibition experiments with a purified carbohydrate moiety clearly showed that the IgE epitope mannose-xylose-fucose-glycan (Man alpha 1-6[Xyl beta 1-2]Man beta 1-4GlcNAc beta 1-4[Fuc alpha 1-3]GlcNAc) or a closely related structure is present in celeriac extract and is important in patients with clinical allergy to celery.