Inhibition of alloantigen-induced cytolytic T lymphocytes in vitro with (2R,5R)-6-heptyne-2,5-diamine, an irreversible inhibitor of ornithine decarboxylase.

The objective of the present investigation was to examine the effect of a new potent irreversible inhibitor of ornithine decarboxylase, (2R,5R)-6-heptyne-2,5-diamine (MAP) (MDL 72,175), on the induction of functionally reactive T-cell populations in vitro. We examined alloantigen-activated cytolytic T lymphocytes (CTL) and T-helper (TH) lymphocytes generated during a one-way mixed-leukocyte culture (MLC). The addition of MAP (1 mM) at the initiation of cell culture reduced intracellular putrescine, spermidine, and spermine levels by 81.9, 82.4, and 55.8% respectively. MAP reduced CTL induction 93.8, 78.4, and 37.5% when added at 0, 24, or 48 hr of culture, respectively. A dose-dependent inhibition of CTL induction and polyamine levels was observed following MAP treatment. In direct comparison with another ODC inhibitor, alpha-difluoromethylornithine (DFMO), MAP was five- to sixfold more potent in reducing CTL induction. CTL generation is dependent upon the endogenous production of the TH-cell product interleukin 2 (IL-2). MAP treatment reduced detectable IL-2 activity in a MLC by 54.8%. These results indicate that MAP is a potent inhibitor of alloantigen-activated CTL in vitro and deserves further investigation as a potential immunosuppressive agent.