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Specific IgE to proteins from Tribolium confusum (TC), a flour beetle, was detected in 9/125 sera of subjects exposed to rye and wheat flour. TC RAST was not inhibited by Dermatophagoides pteronyssinus, rye or wheat flour. Immunoblot experiments showed specific binding to three proteins from adult TC or pupae, not present in rye or wheat flour. These findings suggest that TC might act as an occupational allergen in a proportion of bakers. Correspondence to: PD Dr. Gerhard Schultze-Werninghaus, Division of Pneumology, Department of Internal Medicine, University Hospital, Theodor-Stern-Kai 7, D–W–6000 Frankfurt/Main 70 (FRG) Introduction Baker’s asthma is the most common type of occupational asthma in many countries. Common allergens are proteins from wheat or rye flour [1, 2]. Another increasingly important source of allergens is a number of enzymes, e.g. alpha-amylase from Asper-gillus oryzae [3]. In a preliminary study we had identified a number of arthropode species in flour dust from bakeries. Subsequently, positive skin prick tests to a predominant beetle, Tribolium confusum (TC; confused flour beetle, rice flour beetle), were detected in 8.3% of 133 bakers, using a crude TC extract. Immediate type or dual reactions were seen after bronchial provocation tests with these TC extracts in TC skin prick test positive subjects, even if skin prick tests and bronchial provocation tests with flour extracts were negative [4]. Therefore, this study was performed to prove that TC is an occupational allergen in bakers and that this reaction is IgE mediated. Material and Methods We cultured a TC population (kindly supplied by the Beetle Lab., Hoechst AG, FrankfurtHoechst, FRG) without wheat or rye flour. After 4 months different stages of the beetle were separated: adult beetles (ATC), pupae (TCP), larvae (TCL), exuviae (TCH), and excrements (TCE). These materials were kept at -20°C, ground mechanically, defatted, extracted, and dialyzed. Proteins were coupled to cyanogen bromide-activated methylcellulose disks. D ow nl oa de d by : 54.70.40.11-10/30/201711:37:26PM Sera from 125 bakers were investigated for specific IgE antibodies by enzyme immunoassay(Phadezym RAST, Pharmacia) and RAST inhibition. As controls we used a pooled serum frompollen-allergic subjects (IgE 450 kU/1), sera from 10 atopic subjects (IgE 120–1,000 kU/1) and 9nonatopic subjects (IgE < 80 kU/1).TC extracts, together with extracts from wheat and rye flour, and Dermatophagoidespteronyssinus (Dpt) were further investigated by SDS-PAGE and Immunoblot, using 7 TC IgEantibody-positive and 6 negative sera.ResultsNine of 125 sera (7.2%) had IgE antibodies to ATC (binding rates 11–69%). None of the controlsera showed any binding. RAST inhibition with 5 ATC IgE-positive sera and ATC disks resultedin a mean inhibition of 90% (ATC), 87.5% (TCP), 89% (TCL), 65% (TCH), and 76% (TCE),respectively (fig. 1). In 7⁄8 sera, wheat or rye flour-extracts were also inhibited significantly.Protein fractions of ATC, TCP, and TCE were detected by SDS-PAGE, with a MW between 10and 180 kD. In the sera of bakers, but not in controls, 3 IgE-binding protein fractions (MW 67,85, 132 kD) were seen with ATC and TCP. No corresponding IgE-binding fractions weredetected in flour extracts.372 Schultze-Werninghaus/Zachgo/Rotermund/Wiewrodt/Merget/Wahl/Burow/zur Strassen10080-6040-2010 μl Allergen0.01 SerumG.MFig. 1. RASTinhibition experiment with serum from a subjectwith IgE toTC (RAST). Inhibition by ATC (adult TC),TCH (TCexuviae), TCL (TC larvae), D.pt. (house dustmiteD.pteronyssi-nus), W.F1. (wheat flour), R.F1.(ryeflour), TCP (TC pupae) and TCE (TCexcrements). No significant inhibition wasfoundwith flour extracts or D.pt.ReferencesWalsh BJ, Wrigley CW, Musk AW, Baldo BA:Acomparison of the binding of IgE in the sera ofpatients with baker’s asthma to soluble and insoluble wheat-grain proteins. J Allergy ClinImmunol 1985;76:23–28.Theobald K, Thiel G, Kallweit C, Ulmer W, König W: Detection of proteins in wheat flourextracts that bind human IgG, IgE, and mouse monoclonal antibodies. J Allergy Clin Immunol1986;78:470–477.Baur X, Weiss W, Sauer W, Fruhmann G, Kimm KW, Ulmer WT, Mezger VA, Woitowitz JH,Steurich FK: Backmittel als Mitursache des Bäckerasthmas. Dtsch Med Wochenschr 1988;113:1275–1278.Schultze-Werninghaus G, Wolff H, Bergmann E-M, zur Strassen R: Mehlkäfer (Triboliumconfusum) als Berufsallergen bei Bäckern. Allergologie 1987;10:416–417.Conclusions Downloadedby: 54.70.40.11-10/30/201711:37:26PM Specific immunoglobulin E to TC allergens is frequent in bakers. Extracts from adult TC orpupae contain at least three different proteins with allergenic activity. These proteins differ fromflour proteins. In a proportion of bakers, beetles such as TC may act as occupational allergens. Downloadedby: 54.70.40.11-10/30/201711:37:26PM