Isolation and characterization of Russian thistle (Salsola pestifer) pollen allergens

The radioallergosorbent test (RAST) was utilized to identify allergenically active molecules in an extract of Russian thistle (Salsola pestifer) pollen. Two glycoproteins (RT1 and RT2) were isolated by ion-exchange chromatography, preparative flat-bed electrofocusing, and gel filtration chromatography. These highly purified proteins were similar as judged by discontinuous polyacrylamide gel electrophoresis (PAGE), by PAGE in urea-acetate, and by immunodiffusion analysis. In Ouchterlony double-diffusion, rabbit antiserum to crude pollen extract showed a line of identity between RT1 and RT2. Each allergen possessed a single polypeptide chain, with molecular weight of 39,00 and 42,00 for RT1 and RT2 respectively. Both allergens contained 9.0% +/- 0.5% carbohydrate and 10.6% +/-0.2% nitrogen. Both RT1 and RT2 eluted from a calibrated Sephadex G-100 column near the ovalbumin marker, but the elution volume of RT1 was slightly greater than that of RT2. Amino acid analysis of RT1 and RT2 showed that there was no difference in composition between the two proteins. The proteins showed different isoelectric points (RT1 = 6.7; RT2 6.2). They had similar skin reactivity by Prausnitz-Kustner testing, showed similar potency and identical allergenic qualities as inhibitors in the RAST, and were more potent on a mass basis than crude extract in the inhibition of the reaction between solid-phase crude extract and IgE antibodies in the RAST. RT1 and RT2 represent 0.014% and 0.010% by mass, respectively, of the pollen. These results suggest that RT1 and RT2 are important allergens in Russian thistle pollen. These results suggest that RT1 and RT2 are important allergens in Russian thistle pollen and that these proteins are immunologically identical.