Sunflower (Helianthus annuus) pollen sensitization has been reported as an occupational allergy. In this report, the sensitization of the general population living in sunflower-growing areas to Helianthus pollen was studied. Both RAST results in 32 adults with summer symptoms previously diagnosed as allergic to Artemisia pollen, and cross-reactivity studies between H. annuus and other Compositae suggested that H. annuus pollen was the main allergen involved in the hypersensitivity reaction of those patients. Good correlation was found between RAST and SPT to Helianthus and between RAST and conjunctival provocation test to Helianthus. Bronchial challenge tests performed on 8 of the 32 patients confirmed the clinical implication of Helianthus pollen in suspected subjects. Five workers, handling sunflower pollen, who suffered from related symptoms were subjected to the same study, showing lesser wheal areas and lesser specific IgE levels than a non-worker group. Thirteen patients with RAST values ≥ class 2 showed 2 IgE-binding fractions at 34.0 and 42.8 kD in 65 of sera and 3 IgE-binding fractions at pI 4.9, 9.6 and 10.2 in 54 of sera. By means of micropreparative high-resolution chromatography, it was possible to purify a 34-kD major allergen. Analysis performed by RAST inhibition with sera from atopic patients and ELISA inhibition with experimental anti-Helianthus rabbit sera demonstrated a cross-reactivity between Helianthus and other Compositae, but low affinity of specific anti-Helianthus antibodies for heterologous antigens. Taking into account the above-mentioned data, and the high prevalence of Helianthus pollen in the atmosphere during harvesting (in spite of its entomophilous character), Helianthus pollen should be considered as an allergenic source to be investigated in the general population living in sunflower-growing regions suffering from seasonal summer allerg
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