Cytolytic activity of lymphocytes stimulated with putrescine and all-trans retinoic acid (ATRA) treated dendritic cells (DCs). Immature DCs were from healthy donors and were treated with putrescine (Put) with or without ATRA before DCs pulsed with treated tumour cells (DC-Tuper) preparation. Autologous lymphocytes were stimulated with DC-Tuper, and data are expressed as cytolytic activity (with standard error) against M74 target cell line. Presented data are from seven different donors. Controls are nonstimulated lymphocytes (NSL). Decrease in M74 lysis was repeatedly observed for each of the donors in DC + Put compared with DC, and increased in DC + Put + ATRA as compared with DC + Put. *P < 0.05 versus NSL.