Differential inhibition by azathioprine and 6-mercaptopurine of specific suppressor T cell generation in mice

Doses of 100 mg/kg/day and 55 mg/kg/day of azathioprine (AZ) and 6-mercaptopurine (6-MP), respectively, significantly suppressed anti sheep red blood cell (SRBC) responses in CBA mice, assayed by the complement-dependent cellular cytotoxicity (CDCC) test and by serum titration. Four injections of similar doses of the agents were given to donors of carrier-specific suppressor T cells, generated by two immunizations with SRBC, and transferred to syngeneic recipients sensitized with the TNP hapten on SRBC carrier. Anti-TNP response of the recipients was assayed by the CDCC, using TNP-coated EL4 target cells. Whereas 6-MP, given after or before the second immunization of the donors with carrier SRBC, caused abrogation of suppressor cell activity, equimolar doses of AZ were less inhibitory to suppressor cell generation.