Isolation and characterization of a newly identified antigen from ragweed pollen by organic solvent extraction.

An allergenically active protein, designated as RFB2, was isolated from short ragweed pollen using an aqueous-organic solvent system followed by gel chromatography. Antigen RFB2 was found to be homogeneous based on several criteria, e.g., column chromatography, gel electrophoresis and immunodiffusion. The molecular weight of antigen RFB2 was estimated to be approximately 85,000 daltons based on the results of gel filtration on Sepharose CL-6B. Amino acid analysis revealed that antigen RFB2 contains about twice the amount of leucine and proline and about one-third the amount of cysteine and aspartic acid found in the water soluble antigens AgE, AgK and AgRa3. Antigen RFB2 showed total immunological identity with one of the AgE and the AgK precipitin bands and partial immunological identity with the AgRa3 precipitin band.