Basophil histamine release in patients with birch pollen hypersensitivity with and without allergic symptoms to fruits

Histamine release (HR) studies were performed in 40 birch pollen‐allergic patients (positive case history, positive SPT, positive birch pollen‐specific serum IgE: RAST ≤ 3) with (n= 20, A) and without (n= 20, B) fruit hypersensitivity, and 10 nonatopic volunteers (C). Several fruit allergens were used and characterized by protein determination and immunoblot techniques. Dose‐dependent HR (apple peel = apple pulp> peach = cherry) was demonstrated in both allergic groups, but to a higher extent in patients with fruit allergy (P < 0.01). Increased basophil sensitivity to birch pollen was found in the group with fruit allergy (P < 0.001). Strong correlations between the mediator response induced by several fruits indicate common allergens within the extracts. We conclude that fruit‐related symptoms require not only high specific serum IgE, but a strong cellular sensitization to birch pollen allergens together with an increased cellular reactivity to fruit allergens.