Immunotoxins containing ricin A or B chains with modified carbohydrate residues act synergistically in killing neoplastic B cells in vitro.

Partially deglycosylated (dg) ricin A and B chains were coupled to rabbit anti-human Ig (IT-dg-A) and goat anti-rabbit Ig (IT-dg-B), respectively. The deglycosylation was accomplished by treating intact ricin (before separation into its constituent chains) with a mixture of sodium metaperiodate and sodium cyanoborohydride. The two immunotoxins (ITs) acted synergistically in vitro to kill Daudi cells, albeit to a four-to-eight-fold lesser degree than ITs prepared with native A and B chains.