Induction, maintenance, and reinduction of tumoricidal activity in bone-marrow-derived mononuclear phagocytes by...

Rat bone-marrow-derived mononuclear phagocytes, induced to differentiate in vitro from precursors and virtually homogeneous with respect to the cell lineage, were the source of effector cells. These effector cells do not manifest spontaneous cytolytic activity in the resting state, but readily acquire marked long-term tumoricidal activity upon incubation with macrophage-activating lymphokines (MAF). MAF-induced tumoricidal activity of bone marrow-derived effector cells decays rapidly. However, in sharp contrast to tissue macrophages, bone marrow-derived mononuclear phagocytes retain in vitro responsiveness to a primary exposition to MAF over a period of several weeks, postcytolytic mononuclear phagocytes recover reactivity to MAF after a variable time interval.