ANTIGENIC AND ALLERGENIC RELATIONSHIPS AMONG AIRBORNE GRASS POLLENS IN INDIA

Background: Pollen from grasses (Poaceae) are predominant aeroallergen s throughout the world including tropical countries. Studies from USA, Europe, and Australia have shown extensive allergenic/antigenic cross reactivity among the grass pollen allergens prevalent there. No such information is available about airborne grass pollens of tropical coun tries. Objective: The present study was undertaken to explore common a ntigenic/allergenic components, if any, of five important grass pollen s of India. Methods: Intradermal tests (ID) were performed with pollen extracts of Cenchrus, Cynodon, Imperata, Pennisetum, and Sorghum in p atients with nasobronchial allergy. ELISAs were performed for estimati ng the allergen-specific IgE in sera of patients eliciting markedly po sitive ID response (2+ to 4+). To detect cross reactivity, ELISA inhib ition experiments were carried out using pooled patient sera and five grasses, individually, as inhibitors with different solid phase antige ns. To evaluate common antigenic components in Cenchrus, Imperata, and Pennisetum pollen extracts, rocket immunoelectrophoresis (RIE) and EL ISA inhibition were conducted using rabbit antisera. Results: Among 13 3 patients, Cynodon extract elicited markedly positive skin reactivity in most patients followed by Pennisetum, Imperata, Cenchrus, and Sorg hum. A large number of patients showed markedly positive skin reaction s and enhanced specific IgE levels to more than one grass pollen extra ct. ELISA inhibition experiments showed different degrees of cross rea ctivity among the grass pollens studied. Rocket immunoelectrophoresis and ELISA inhibition using rabbit antisera with homologous and heterol ogous pollen revealed the presence of shared antigenic components in C enchrus, Imperata, and Pennisetum extracts. Conclusion: The varied dos e-response curves obtained with ELISA inhibition using different inhib itors suggest the presence of both common and specific antigens/allerg ens in the grass pollens studied. Based on the extensive immunologic c ross reactivity, among the tropical grass species, it may be possible to use mixed allergen preparations for allergy diagnosis and immunothe rapy.