Two cytotoxic pathways of natural killer cells in human cord blood: implications in cord blood transplantation.

Using K562 cells as a target we investigated cord blood (CB)-natural killer (NK) cytolytic pathways. The cytotoxicity of fresh CB-NK cells was significantly lower than that of peripheral blood mononuclear cells (PB MNCs). When CB was incubated with IL-2, the level of CB-NK cytotoxicity was increased and boosted to the level observed in PB-NK cells. Fresh CB-NK cells induced apoptosis in target cells. Activated CB cells induced apoptosis and necrosis in target cells, at the same level as PB MNCs. CB stem cell transplantation may also induce graft-versus-host disease (GVHD)/graft-versus-leukaemia (GVL), similar to bone marrow transplantation.