Isolation and partial characterization of Bermuda grass pollen allergen, BG-60a

In an earlier study we showed that Bermuda grass (Cynodon dactylon) pollen contains at least 12 IgE-binding proteins that can be analysed by immunoblot technique. One of the active components (BG-60) proved to be a basic protein of glycoprotein nature. It contained about 28% carbohydrate as determined from the dry weight and consisted of four molecules. One of the components was purified from the pollen extract by a combination of ammonium sulphate precipitation, ion-exchange chromatography on carboxymethyl-TSK, gel filtration on Ultrogel AcA 44 and chromatofocusing. Its molecular weight was approximately 60 kD by SDS-PAGE and 34 kD by gel filtration chromatography. The isoelectric point of the antigen was about 9.7. The homogeneity of the antigen BG-60a was assessed by one single arc of immunoprecipitation both in immunodiffusion and crossed immunoelectrophoresis and by one single band after SDS-PAGE. Its allergenicity was demonstrated by direct intradermal skin test on allergic patients and by examining IgE-binding reactivity with allergic patients' serum.