IgE binding to a new cross-reactive structure: a 35 kDa protein in birch pollen, exotic fruit and other plant foods.

Food allergies in birch pollen allergic patients have been shown to be due to cross-reactivities of specific IgE antibodies which are directed against birch pollen allergens with related proteins in fruit, nuts and vegetables. We identified a new cross-reactive structure of 35 kDa in birch pollen and some plant food extracts by Enzyme Allergosorbent Test (EAST) and immunoblot inhibition studies. The 35 kDa birch pollen protein is a minor allergen to which approximately 10-15% of birch pollen allergic individuals have specific IgE. Our data demonstrate that there is cross-reactivity of this protein with proteins of comparable size from lychee, mango, banana, orange, apple, pear and carrot. While the 35 kDa protein is immunologically independent of the major birch pollen allergen Bet v 1, we also observed IgE binding to a 34 kDa structure which appears to be a Bet v 1 dimer.