A ricin-containing immunotoxin with immunotherapeutic property. Ricin, a plant toxin extracted from castor beans, inhibits protein synthesis via cleaving ribosomal subunit 28S rRNA. Ricin immunoconjugate consists of specific antibody conjugated with the blocked ricin (bR), which has the galactose-binding sites of the B-chain blocked while leaving the ribosome-inactivating ricin A-chain intact, thereby attaining cell-type-specific immunotoxins.