Comparative Studies on Tree-Pollen Allergens

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Abstract
A major allergen from birch pollen (B. verrucosa) was isolated by a combination of gel permeation chromatography and preparative isoelectric focusing, and was found adequate for further immunological and chemical characterization. The crude aqueous pollen extract was eluted in 6 UV-absorbance peaks from an Ultrogel AcA-54 column. The main allergenic components were detected in 2 peaks of MW 29,000 (BV4) and 40,000 daltons, respectively. BV4 contained 1 quantitatively dominating antigen as assessed by crossed immunoelectrophoresis, and was selected for further purification by isoelectric focusing. Column isoelectric focusing of BV4 gave 4 protein fractions with pI values corresponding to 5.18, 5.42, 5.76 and 5.94. The pI 5.18 protein was quantitatively dominating. This protein inhibited the radioallergosorbent test in 8 out of 10 sera from birch pollen-sensitive individuals. Using a serum pool, the inhibition curve of BV4 pI 5.18 was parallel to that of the crude extract and gave a similar maximum inhibition. This allergen was homogeneous as judged by a single, symmetrical precipitate in crossed immunoelectrophoresis, 1 band in high-volt electrophoresis and a sharp strip in thin-layer analytical electrofocusing. Amino acid analysis showed a high content of serine. The N-terminal analysis and the carbohydrate concentration were preliminarily reported.

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