Bone marrow mesenchymal stem cells suppressing activation of allogeneic cytokine-induced killer/natural killer cells either by direct or indirect interaction

Bone marrow mesenchymal stem cells (MSC) were recently found to be associated with some special immunological characteristics, the immunoregulatory effect of MSC was dose-dependent. Low amount of MSC was associated with mild immunosuppression or even immune activation, while the high amount of that was associated with significant immunosuppressive effect. In this study, by using a transwell system, we explored the effect of MSC on the cell cycle, apoptosis rate and the expression of CD69, an activation marker, on the allogeneic cord blood derived cytokine-induced killer(CIK)/natural killer(NK) cells. The results showed that either by transwell or mixed cell-cell co-culture, the MSC can effect CIK/NK cells on the cell cycle, such as arrested in the G0/G1 phase, diminished the ratio of cells in S, G2/M phase, and increased the apoptosis of them. MSC can also depress the expression of CD69 on these killer cells, as well as increased the ratio of CD4(+)CD25(+)CD127(low) T regulatory (Treg) cells in the CIK/NK cell culture system. We draw conclusions that either by transwell or mixed co-culture, the MSC can suppress activation of allogeneic CB-CIK/NK cells in a dose-dependent manner.