MSCs interact with T cells and induce a T_H1 to T_H2 shift. Human MSCs were cocultured with hPBMCs from unrelated donors under (A) T_H1-, (B) T_H2-, or (C) T_Reg-inducing conditions as described. In the presence of hMSCs, there was a more than 50% decrease in IFN-γ secreted from T_H1 cells compared with controls without hMSCs present (IFN-γ levels secreted by T_H1 cells alone = 100%). For T_H2 cultures, there was a more than 500% increase in IL-4 produced when hMSCs were present (control T_H2 cells = 100%). Bars indicate the change in cytokine levels (mean % change ± SD) in cultures incubated with or without hMSCs from 3 independent experiments. For T_Reg cultures, the proportion of CD4⁺CD25⁺ cells from 5 experiments is plotted. Results indicated that when hMSCs were present, there was a consistent increase in the proportion of CD4⁺CD25⁺ T_Regs. (D) A representative flow diagram from one experiment in which T_Regs were generated with or without hMSCs is shown.