Isolation and partial characterization of antigen 5.1 from the seeds of Ricinus communis, L. (Var. Amarelo de Irece).

Antigen 5.1 was isolated from the most acidic fraction of castor bean allergens (CB-1A) by gel filtration on Sephadex G-75 followed by polyacrylamide gel electrophoresis (PAGE) (yield: 6.2 mg antigen 5.1/g CB-1A). This antigen was homogeneous by the criteria of PAGE, isoelectric focusing, SDS-PAGE, immunoelectrophoresis and gel filtration. The antigen has an apparent molecular mass of 12 +/- 2 kDa and an isoelectric point of pH 5.1. Antigen 5.1 lacks proline, phenylalanine, threonine and tryptophan. It was immunochemically identical to one of the three immunoprecipitation lines presented by CB-1A by the Ouchterlony technique, and was positive when tested (250 micrograms) by IgE-mediated passive cutaneous anaphylaxis in LOU.M rats.