[Cytotoxicity of a conjugate of ricin A-chain and monoclonal anti-allotypic antibody]. / Izuchenie tsitotoksicheskikh svoistv kon"iugata A-tsepi ritsina i monoklonal'nykh antiallotipicheskikh antitel.

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.

Monoclonal antibodies against common and Igk-1a allotypic determinants of rat immunoglobulin kappa chain constant domain.

SJL/J mice were immunized with polyclonal rat Ig light chains of two allotypes and immune spleen cells were fused with P3-Ag8.653 myeloma cells. 17 cell populations producing antirat Ig AB were cloned. Four clones, 1G9, L3E8, L2B2 and L2C5 have been characterized in detail. All MABs are of the IgG1, kappa isotype. Using monoclonal rat kappa chains it was demonstrated that all the AB react with rat Ig kappa chains. Further localization of antigenic determinants was performed using isolated L chain C domain. It was shown that all MABs are directed against C domain epitopes. L2C5 MAB binds selectively to August rat L chains, thus showing specificity for Igk-1a determinants. The remaining three clones bind equally well to L chains of different allotypes, but 1G9 clone binds preferentially to isolated L chains as compared to intact IgG molecules.