Immunotoxins: current use and future prospects in bone marrow transplantation and cancer treatment.

Immunotoxins are protein toxins which have been conjugated in whole or in part to antibodies in the hope of producing cell-type-specific toxic reagents with useful properties. Such reagents hold the promise for eliminating unwanted cells both in vivo and in vitro. In practice, to date, only in vitro usage has proven clinically and experimentally useful. The design of effective immunotoxins is based on utilizing cellular entry mechanisms or entry mechanisms inherent in the parent toxins to cross the plasma membrane barrier to the cytosol compartment where the toxins exert their effects. Knowledge in the area of receptor-mediated protein transport is expanding rapidly and new immunotoxins with increased efficiencies are anticipated.