EFFECT OF HYPOSENSITIZATION FOR TREE POLLINOSIS ON ASSOCIATED APPLE ALLERGY

Twenty patients suffering from birch pollen allergy received two or th ree courses of immunotherapy in successive years. In 9 patients, the f ruit allergy improved; 4 patients reported no improvement. In 3 patien ts, the fruit allergy developed after beginning the immunotherapy. At the end of the 3 years, 16 of these patients were allergic to fruit, 1 3 of them to apple. After each preseasonal course of immunotherapy wit h tree pollen extract, a temporal and parallel increase in the titers of IgE antibodies to birch pollen allergens and apple allergens were o bserved. In contrast, only the titers of birch pollen allergen specifi c IgG and IgG4 increased, whereas apple allergen specific IgG and IgG4 did not, or only very slightly. In Western blot studies, IgG4 antibod ies bound to more components of apple extract than birch pollen extrac t. On the average, IgG4 antibodies recognize more components of apple and birch pollen extracts than do IgE antibodies. In histamine release studies, the sensitivity of washed leukocytes to birch pollen extract decreased significantly during the observation time. However, the dif ference between apple extract-induced histamine release before and aft er immunotherapy was not significant. None of the immunological parame ters investigated here correlate well with severity or prognosis of th e fruit (apple) allergy. The clinical improvement of pollinosis was as sociated with a rise in birch pollen specific IgG4 antibody titers and a decrease of allergen-induced histamine liberation. Beside improveme nt of the fruit allergy in 56% of the cases, the courses of apple spec ific IgE and IgG4 antibody titers seem to indicate a slight sensitizat ion against apple allergens.