[Effect of antipurine antibodies on the immunodepressive activity of 6-mercaptopurine].

In repeated injections of 6-mercaptopurine (6-MP) covalently bound with protein (6-MP-P) antibodies binding 6-MP appeared in rabbits. In such animals free 6-MP produced a lesser immunodepressive and toxic action. Injection to mice immunized with sheep erythrocytes (SE) of rabbit serum containing antibodies against 6-MP not only failed to lead to reduction of the immunodepressive action of this cytostatic, but, on the contrary, intensified the inhibition of antibody formation to the SE. Injection to mice of 6-MP bound with rabbit antiserum in vitro also enhanced its immunodepressive activity. Evidently own antibodies neutralized 6-MP, whereas foreign ones, serving as an antigen, apparently caused its accumulation in the macrophagal lymphocytic complex.