A subset of walnut allergic adults is sensitized to walnut 11S globulin Jug r 4.

BACKGROUND: The role of sensitization to commercially available allergens of English walnut (Juglans regia) Jug r 1, 2 and 3 in walnut allergy has been previously investigated in walnut allergic adults and was unable to explain all cases of walnut allergy. OBJECTIVES: Identify recognized walnut allergens, other than the ones previously investigated (Jug r 1-3), in walnut allergic adults and determine the sensitization frequency and diagnostic value. METHODS: Three different in-house walnut extracts were prepared and analysed on SDS-PAGE blots to identify allergenic walnut proteins. Immunoblots and immunoprecipitation, followed by LC-MS analysis, were performed to screen for, and confirm, IgE binding to walnut allergens in selected walnut allergic adults. In a cohort of 55 walnut challenged adults, including 33 allergic and 22 tolerant, sensitization to native and recombinant walnut allergen Jug r 4 was assessed using immunoblotting and immuno-line blot (EUROLINE), respectively. RESULTS: Screening of sera of 8 walnut allergic adults identified Jug r 4 as an allergen in our population. In the total cohort of 55 subjects, 5 were positive for Jug r 4 on immunoblot and 10 on EUROLINE. All but one EUROLINE positive subject had a positive food challenge (sensitivity 27%, specificity 95%, PPV 90%, NPV 47%). All 5 subjects positive on immunoblot were also positive on EUROLINE. LC-MS analysis showed a lack of Jug r 4 in the ImmunoCAP extract. Co-sensitization to other 11S albumins (eg hazelnut Cor a 9) was common in Jug r 4 sensitized subjects, potentially due to cross-reactivity. CONCLUSIONS: Walnut 11S globulin Jug r 4 is a relevant minor allergen, recognized by 27% of walnut allergic adults. It has a high positive predictive value of 90% for walnut allergy. Specific IgE against Jug r 4 occurred mostly with concomitant sensitization to other walnut components, mainly Jug r 1.

Cross-reactivity among the pollen proteins of birch and apple trees.

In the spring of 1986, the pollen were collected from apple trees in full blossom, and were investigated for their allergenicity. The patients selected for study were subjects with a combined inhalant allergy to birch pollen and an oral allergy to apple fruit. The apple pollen extract yielded about the same percentage of nondialysable substance as obtained from birch pollen. In contrast to the latter, UV-spectroscopy revealed no flavonoids adsorbed to the apple pollen proteins. Patients with a combined allergy to birch pollen and apple fruit showed positive skin reactions to both birch and apple pollen extract. Inhibition of IgE-binding in RAST to birch pollen was observed by apple pollen extract at a 1000-fold lower potency than the homologous birch allergens. Immunoblotting demonstrated IgG-antibodies in birch-allergic sera cross-reactive with apple pollen components. It is concluded that minor allergenic determinants cross-reactive with birch pollen epitopes occur not only in the fruit, but also in the pollen of the apple tree.