Cancer research
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Pokeweed antiviral protein (PAP) and ricin A chain are potent inhibitors of protein synthesis that inactivate eukaryotic 60S ribosomal subunits. Immunotoxins were prepared by linking monoclonal anti-Thy 1.1 antibodies to PAP and ricin A chain through a disulfide bond. Both the conjugates were shown earlier to specifically inhibit protein synthesis of Thy 1.1-positive target leukemic cells (AKR SL3). ⋯ These observations indicate that the use of alternate immunotoxins having an immunologically distinct toxin polypeptide may be necessary for tumor therapy during relapse, as exposure to the conjugates results in the formation of specific neutralizing anti-toxin antibodies. The anti-toxin antibodies did not prevent the binding of immunotoxin to target cells. Nevertheless, preincubation of conjugate with anti-toxin antibodies specifically blocked the respective conjugate-induced inhibition of polyuridylic acid translation in a cell-free assay system.