A radioimmunoassay employing cephalothin linked to a solid phase has been developed for the detection of cephalosporin-reactive IgE antibodies. Direct binding and inhibition studies demonstrated allergenic cross-reactivity between cephalosporins and penicillins, and quantitative hapten inhibition experiments identified the 2-thiophene group, and particularly the attached methylene group, of cephalothin as an allergenic determinant.

Sera from two subjects with bakers* asthma and six patients with coeliac condition were examined for the presence of IgE antibodies with specificities for wheat flour components. Sera were studied using the radioallergosorbent test (RAST) together with whole flour and thirteen purified and partially purified fiour fractions.IgE antibodies to a number of flour components were demonstrated in the allergic bakers' sera, but the strongest reactivities were observed with wheat albumins and globulins. A more detailed examination of the flour water-soluble proteins using RAST inhibition methods demonstrated that albumins were more reactive with the allergic sera than the globulins. Apart from the results with the water-soluble proteins, the two sera showed a different pattern of reactivity with the other flour preparations.No IgE antibodies to whole flour or any of the flour components, including A gliadin, were found in the coeliac sera. Failure to detect wheat gluten-or gliadinspecific IgE antibodies indicates that IgE-mediated reactions are not important in the pathogenesis of coeliac condition. Levels of total IgE in the sera from the coeliac subjects were elevated and, with two of the sera, some success was achieved in identifying the allergens responsible for the elevation. We propose that elevation of serum IgE may frequently occur in coeliac condition and may arise due to an increased uptake of antigens via the damaged intestinal mucosa.

Unlike studies on the antigenicity of penicillins in laboratory animals, limited information is available on the allergenicity of penicillins in man, especially with regard to fine structural allergenic differences between the many different penicillins. Inconsistent with the earlier conclusions of others, our studies suggest that side-chain structures on the penicillin molecule are the major allergenic determinants in many reactions. Immediate allergic reactions to flucloxacillin were observed in a number of patients where diagnosis was confirmed by skin testing and detection of flucloxacillin-reactive IgE antibodies. Quantitative hapten inhibition studies revealed potent inhibition by flucloxacillin and three structurally related penicillins: oxacillin, cloxacillin and dicloxacillin. Analysis of the inhibition results showed that the side-chain group of flucloxacillin, 3-(2-chloro-6-fluorophenyl)-5-methyl-4-isoxazolyl, is recognized by some antibodies and that the 5-methyl-3-phenyl-4-isoxazolyl group, with or without halogen substituents, accounts for the reactivity of other antibodies and for the cross-reactions seen with some other penicillins. Since it is the side-chain group that distinguishes the many different penicillins, and since the side-chain groups are recognized by IgE antibodies in many of the allergic reactions, it is becoming clear that specific assays are required for the detection of IgE antibodies to each of the different penicillins.

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