Induction of alloreactive immunosuppression by 1,4-bis [( 2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (CL 232,468)

1,4-bis[2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione (AEAD) has been investigated for its potential immunosuppressive effect on cell-mediated immune responses. Addition of the compound to mixed lymphocyte cultures (MLC) not only significantly inhibited these cells from responding to alloantigens but also prevented the induction of cytolytic T lymphocytes (CTL). A structurally related compound, mitoxantrone, was also found to be active in inhibiting CTL induction. AEAD had to be present during the first 3 days of a 5-day MLC in order to produce a significant effect and it had no effect on those CTL already generated, suggesting that it acted upon induction of CTL rather than the effector phase. Lymphocytes from mice treated with the compound were incapable of responding to alloantigens in vitro and the effect was dose- and time-dependent. Furthermore, lymphocytes from treated mice were found to inhibit CTL generation from normal mouse lymphocytes, indicating that a suppressor cell population might be induced in the spleens of Animals treated with the compound. The present findings clearly demonstrate that AEAD is a compound with potent immunosuppressive activity on alloreactive immune responses.