[Cytotoxicity of a conjugate of ricin A-chain and monoclonal anti-allotypic antibody].

A conjugate was developed between ricin A-chain and monoclonal antiallotypic antibody specific for L-chains of the rat Ig. Incubation of spleen cells with the conjugate (10(-7) M) resulted in a strong decrease of 1a-positive B-lymphocyte growth. At the same time spleen cells that lacked this antigen were not affected by immunotoxin (IT). Both the isolated antibodies and ricin A-chain did not inhibit cell growth in the same concentrations. IT injection to 10-day-old heterozygous rats (1a/1b) resulted in a partial suppression of Ig production with 1a-allotype. The conjugate was 4.5 times more effective than the isolated antibodies used to form it. The in vivo and in vitro differences in IT cytotoxicity were probably connected with insufficient efficacy of conjugate targeting in vivo.