Fractionation of castor bean allergens (CB-1A). Isolation of RC-13, a homogeneous allergenic fraction.

Allergens from castor beans (CB-1A) were fractionated by ion-exchange chromatography both on CM- and SP-Sephadex, employing pH gradient. SP-Sephadex showed better results and fractionated the allergens into 7 components, eluted in a narrow pH range (5.0 - 6.6). An attempt to isolate the major acidic fraction of the group involved successive chromatographic steps on the same gel. RC-13, the isolated fraction, proved homogeneous by rechromatography on SP-Sephadex and isolectric focusing with pH range 3.0 - 10.0 polyacrylamide gel. The pl of RC-13 determined by the latter is approximately 4.2 and allergenic activity was demonstrated by heterologous passive cutaneous anaphylaxis in mice using anti-CB-1A rabbit serum.