CHARACTERIZATION OF THE 18-KDA APPLE ALLERGEN BY 2-DIMENSIONAL IMMUNOBLOTTING AND MICROSEQUENCING

A low-temperature extract taken from Golden Delicious apples was separ ated by two-dimensional polyacrylamide gel electrophoresis. By means o f two-dimensional immunoblotting with patients' serum containing IgE s pecific to Bet v I, a rabbit polyclonal antiserum raised against Bet v I, and two Bet v I specific monoclonal antibodies, epitopes cross-rea ctive to Bet v I were identified on an apple allergen with a molecular mass of 18 kDa and pI 5.5. Furthermore, certain antibody reactivities with 4 isoproteins of a molecular mass of 16 kDa and pIs ranging from 4.9 to 5.5 were observed, which may indicate the presence of Bet v I related epitopes on these proteins. Based on 26 amino acid residues, N -terminal sequencing of the 18-kDa apple allergen revealed 62% sequenc e identity between Bet v I from birch pollen and the apple allergen. O ur results therefore support the view that both proteins express commo n as well as non-related IgE-reactive epitopes.