Skin-prick test and RAST responses to cereals in children with atopic dermatitis. Characterization of IgE-binding components in wheat and oats by an immunoblotting method.

Abstract

Hypersensitivity to cereals may occur via inhalation or ingestion. Although cereals are essential in the daily nutrition, only little information is available of the allergens causing symptoms in patients with atopic dermatitis (AD). The purpose of the present study was to analyse the IgE immune-response to various cereals and specific cereal fractions of wheat and oats in children with severe AD and correlate the results with challenge studies. Skin-prick tests (SPT) with a NaCl suspension of wheat, oats, rice, corn, millet and buckwheat and the ethanol soluble gliadin fraction of wheat were performed to 34 wheat/oats challenge positive or negative children with AD. Simultaneously serum total IgE and specific IgE antibody radioallergosorbent test (RAST), levels to wheat, oats and gluten were determined. In addition serum samples of these 34 AD patients and five age matched controls were analysed with IgE immunoblotting using neutral and acidic protein extracts of wheat and oats. From the 34 AD children 33 were SPT positive with wheat and 18 with oats. Positive RAST to wheat and oats could be detected in 32 and 30 samples respectively. From the oral wheat challenge positive children 12/14 appeared positive with gliadin SPT and revealed positive RAST to gluten, but each of the wheat challenge negative were negative in SPT with gliadin. In immunoblotting using neutral and acidic fractions of cereals the IgE binding with sera of challenge positive children showed the most intensive staining, but no correlation was found between different staining patterns and the clinical wheat sensitivity. The 26, 38 and 69 kDa bands in wheat and the 46 and 66 kDa in oats could be classified as major IgE binding proteins of these cereals (> 50% of the sera were positive). SPT with rice, corn, millet or buckwheat was positive in 16/34 patients. Intensive IgE staining to neutral/acidic soluble proteins in wheat and oats was seen, with major IgE binding to 26, 38 and 69 kDa proteins in wheat and 46 and 66 kDa in oats, but no specific IgE staining patterns correlating with clinical cereal sensitivity were found. The strong association between the positive oral wheat challenge and the positive SPT with the ethanol soluble gliadin suggests that also gliadin is an important allergen in wheat-allergic children with AD. The allergens in rice, corn, millet and buckwheat should be better studied before they can be recommended as alternatives for cereal allergic children.