Aerobiologic and immunochemical studies on Borassus flabellifer pollen: evidence for a 90-kD allergen.

BACKGROUND

The pollen grains of Arecaceae have been proved to be a very common aeroallergen in India. Except for the pollen grains of Cocos nucifera, detailed information about the allergenicity of other dominant Indian palm pollen is not available.

OBJECTIVE

To explore the aerobiologic and allergenic significance of the pollen of palmyra palm (Borassus flabellifer Linn.), one of the important and common palm trees in India, with a view to isolate and purify its major allergenic components.

METHODS

The aerobiologic survey was performed continuously using Burkard volumetric and Rotorod samplers from July, 1994 to June, 1996 in a northern suburb of greater Calcutta. The allergenic potential of the pollen extract and different fractions were studied by skin prick tests (SPT). ELISA and ELISA inhibition experiments were performed with individual and pooled patient sera to detect the specific IgE level. By 2-step ammonium sulphate fractionation and gel filtration study, the allergic fraction Fr.IIA1 was isolated. Its molecular weight was determined by SDS-PAGE and homogeneity was confirmed by rocket and crossed immunoelectrophoresis using rabbit antisera.

RESULTS

Pollen grains of B. flabellifer were found to be present in air from February to May and June contributing more than 7% of the total airborne pollen load of the study area. The pollen elicited maximum concentration at 19 to 20 hours in the evening and at a height of 4 m from ground level. Skin prick testing of 455 respiratory allergic patients with whole pollen extract exhibited 31.64% positive response. After 2-step ammonium sulphate fraction and gel filtration, a fraction (Fr.IIA1) having remarkable allergenicity was isolated. In native and SDS-PAGE, it was found as a single protein component of 90 kD and as homogeneous in RIE and CIE. The soluble protein-carbohydrate analysis indicated the probability of the component to be a glycoprotein.

CONCLUSIONS

The aerobiologic, clinical, and immunochemical, studies demonstrated that the pollen of B. flabellifer is a dominant aeroallergen to cause respiratory trouble in the area where these trees grow. The isolated 90-kD component is one of the major allergens present in the pollen extract.