It is known that most patients with type I
allergy to tree pollens also suffer from intolerance to nuts. To identify allergenic structures common to hazel pollen and hazelnuts, cross-reactivity of patients'
IgE was investigated. With use of immunoblotting,.serum
IgE from 25 patients displaying type I
allergic reactions to tree pollens and intolerance to hazelnuts (group I) bound to the 17 kd major hazel pollen
allergen Cor a I (100%) and to the 14 kd hazel pollen
profilin (16%).
IgE binding to
proteins of comparable molecular weights in hazelnut extracts was found (18 kd and 14 kd), suggesting that
proteins similar to Cor a I and hazel
profilin might be also expressed in hazelnuts. In contrast, only four sera (22%) from 18 patients (group II) with tree
pollen allergy but without any case history of
nut hypersensitivity showed
IgE binding to the 18 kd
protein of hazelnut extract, and none of these sera exhibited
IgE reactivity to the hazelnut
profilin. To characterize the hazel pollen and hazelnut
allergens, purified recombinant Bet v I (major birch pollen
allergen) and purified recombinant Bet v II (birch
profilin), respectively, were used for
IgE-inhibition experiments. Binding of
IgE from patients (with
nut allergy) to the blotted hazelnut
allergens could be blocked by preincubation of patients' sera with the
recombinant proteins. Furthermore, the 18 kd
protein of hazelnut extract was purified and induced specific release of
histamine from basophils of a patient suffering
nut hypersensitivity but not from a healthy control donor. A rabbit antibody raised against celery
profilin identified the 14 kd
proteins in hazel pollen and hazelnuts as
profilin. Our experiments suggest a
protein with
IgE binding properties similar to the major
allergens from pollens of hazel, Cor a I, and of birch, Bet v I, as predominant
allergens in hazelnuts, and show that the plant pan-
allergen profilin can be detected in both hazel pollen and hazelnut extracts.