Further characterization of IgE-binding antigens in horse dander, with particular emphasis on glycoprotein allergens

IgE-binding components in an extract of horse dander were analyzed, especially with regard to the glycoprotein allergens. After SDS-PAGE under reducing conditions and blotting, several of the glycoprotein IgE-binding components, including two distinct bands of 27 and 31 kDa, were detected. Together with several other bands, they were shown to bind to the lectins Sambucus nigra agglutinin (SNA) and Datura stramonium agglutinin (DSA), indicating terminal sialic acid linked alpha 2 --> 6 to galactose, and galactose linked beta 1 --> 4 to N-acetylglucosamine, respectively. Carbohydrate analysis after SDS-PAGE and blotting showed the presence of mannose, galactose, N-acetylglucosamine, and N-acetyl neuraminic acid in the 27-kDa band. The 14.4-kDa glycoprotein component lost its IgE-binding activity after periodate oxidation. Minor differences in allergenic activity in the other glycoprotein allergenic components were also detected, indicating that the carbohydrate part of the molecule seems to play a role in the IgE-binding activity. Two-dimensional electrophoresis and subsequent immunoblotting were performed to estimate the approximate number, molecular mass, and pI of IgE-binding components. This resulted in a cluster of such components on the blot membrane.