IgE-binding activity to enzyme-digested ovomucoid distinguishes between patients with contact urticaria to egg with and without overt symptoms on ingestion
Article first published online: 24 DEC 2001
Volume 55, Issue 6, pages 565–569, June 2000
How to Cite
Yamada, K., Urisu, A., Koyama, H., Tokuda, R., Wada, E., Kondo, Y., Ando, H., Morita, Y. and Torii, S. (2000), IgE-binding activity to enzyme-digested ovomucoid distinguishes between patients with contact urticaria to egg with and without overt symptoms on ingestion. Allergy, 55: 565–569. doi: 10.1034/j.1398-9995.2000.00430.x
- Issue published online: 24 DEC 2001
- Article first published online: 24 DEC 2001
- Accepted for publication 3 February 2000
- contact urticaria;
- egg hypersensitivity reactions;
- oral challenge;
- RAST inhibition
Background: We occasionally see egg-allergic children who develop contact urticaria to hen's egg despite the absence of the overt symptoms on ingestion. The mechanisms remain to be elucidated.
Methods: Twenty-one subjects with positive reactions to 20-min patch tests for egg-white antigens were divided into subgroups with positive (n=10) and negative (n=11) results to oral challenge tests by the same antigens. We measured IgE antibody for egg white and its components, and IgE-binding activities to digestive enzyme-treated ovomucoid by RAST inhibition.
Results: There were no significant differences in IgE antibody titers to egg white (positive vs negative: 30.3%vs 15.3%, P=0.130), ovomucoid (21.5%vs 10.2%, P=0.078), ovotransferrin (9.9%vs 3.7%, P=0.105), and lysozyme (3.4%vs 2.9%, P=0.944), except ovalbumin (16.8%vs 5.6%, P=0.024), between the positive and negative subjects in the provocation tests. In contrast, the concentration (1.93 μg/ml) of pepsin-treated ovomucoid needed for 50% RAST inhibition in the challenge-positive subjects was significantly (P=0.0003) lower than that(114.9 μg/ml) of negative subjects. Similar but less significant differences were obtained when ovomucoid fragments treated with chymotrypsin (0.91 μg/ml vs 6.86 μg/ml, P=0.014) and trypsin (0.75 μg/ml vs 4.67 μg/ml, P=0.041) were used as inhibitors.
Conclusions: We suggest that IgE antibodies from subjects showing contact urticaria despite the absence of reactions to the ingestion of egg white recognize the epitope(s) unstable to digestive enzymes.