Sensitization to blackgram in patients with bronchial asthma and rhinitis: clinical evaluation and characterization of allergens.

BACKGROUND

Legumes are important causative agents of type I hypersensitivity in south Asia and Europe but such studies are lacking in Indian population. The present study investigates blackgram sensitization in asthma and rhinitis patients and identifies immunoglobulin E (IgE)-binding proteins.

METHODS

Respiratory allergy patients were evaluated using standard questionnaire and skin prick tests (SPT) with common foods and aeroallergens. Blackgram-specific IgE level was estimated by enzyme-linked immunosorbent assay (ELISA) and sensitization was established by a double-blind, placebo-controlled food challenge (DBPCFC). The cross-reactivity of blackgram with other legumes was studied by immunobiochemical methods.

RESULT: Of 816 patients, 35 gave history of blackgram hypersensitivity. From these, 16 patients were SPT positive and 14 showed elevated specific IgE (three times of negative control) to blackgram. DBPCFC established blackgram sensitivity in four of 14 patients. Immunoblotting with individual patient's sera recognized eight most prevalent allergens of 78, 56, 47, 43, 40, 30, 28 and 16 kDa. Roasted blackgram showed six major allergens whereas 47, 43 and 28 kDa proteins retained IgE reactivity upon boiling. Blackgram extract required 14 ng of self protein for 50% ELISA inhibition whereas roasted and boiled blackgram required 16 and 120 ng protein. ELISA and immunoblot inhibition show partial inhibition to blackgram proteins by lentil, limabean and pea.

CONCLUSION

Blackgram induces IgE-mediated reactions in 1.7% of asthma and rhinitis patients and contains eight major IgE-binding components, of which six retained IgE reactivity after roasting. Blackgram shares allergenicity with lentil and limabean.