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Background: Several wheat flour allergens relevant to baker's asthma have been identified in the last 25 years. The aim of this study was to determine the frequency of sensitization to these allergens in German bakers. Methods: Using recombinant DNA technology, the following wheat flour allergens were cloned, expressed in Escherichia coli and purified: five subunits of the wheat α-amylase inhibitors (WTAI-CM1, WTAI-CM2, WTAI-CM3, WDAI-0.19 and WMAI-0.28), thioredoxin, thiol reductase or 1-cys-peroxiredoxin homologues, triosephosphate-isomerase, αβ-gliadin, serpin, glyceraldehyde-3-phosphate-dehydrogenase, a nonspecific lipid transfer protein (nsLTP), dehydrin, profilin and peroxidase. In addition, ImmunoCAPs with the recombinant allergen ω-5-gliadin and two cross-reactive carbohydrate determinants (CCDs), horse radish peroxidase (HRP) and the N-glycan of bromelain (MUXF), were used. Specific IgE was measured in wheat flour-positive sera from 40 German bakers with work-related asthma/rhinitis and 10 controls with pollinosis. Results: Thirty bakers (75%) had IgE to at least one of the 19 single allergens. Most frequent was IgE to WDAI-0.19, HRP and MUXF (25% each), followed by WTAI-CM1 (20%), thiol reductase (16%), WTAI-CM3 (15%), WTAI-CM2 and thioredoxin (12.5%), WMAI-28, triosephosphate-isomerase, αβ-gliadin (10%), 1-cys-peroxiredoxin (7.5%), dehydrin, serpin, glyceraldehyde-3-phosphate-dehydrogenase (5%), ω-5-gliadin, nsLTP and profilin (2.5%). Fifteen bakers (38%) had IgE to any α-amylase inhibitor and 12 (30%) to at least one CCD. The controls reacted exclusively to CCDs (80%), profilin (60%), thioredoxin (30%), triosephosphate isomerase and nsLTP (10%). Conclusions: The single allergen sensitization profiles obtained with 17 recombinant wheat flour allergens and two CCDs revealed no major allergen for German bakers. The highest frequencies were found for α-amylase inhibitors and CCDs. [ABSTRACT FROM AUTHOR]