Binding of antibodies against birch pollen antigens/allergens to various parts of apples as studied by immuno-gold electron microscopy

The clinically and biochemically observed correlation between birch pollen allergy and hypersensitivity to apples was investigated by immunocytochemical techniques. For this purpose, apple tissue was fixed in p-formaldehyde and embedded in Lowicryl K4M resin at -35 degrees C. Ultrathin sections were cut and successively incubated with rabbit antibodies against birch pollen antigens/allergens and protein A/gold. Specific antibody binding sites were detected throughout the apple fruit (peel, fruit flesh, seed). Control sections incubated with normal rabbit IgG antibodies and protein A/gold showed minimal background staining. It was concluded from the results of immunocytochemical labelling that apple tissue and birch pollen contain similar molecular structures which lead to the observed cross-reactions. The present immunocytochemical results confirm biochemical investigations reporting partial structural identity of antigens/allergens in birch and apple.