MSCs inhibit the response of naive antigen-specific T cells in a dose-dependent fashion.

Splenocytes from C6 mice transgenic for a K^k-restricted HY-specific TCR were stimulated with irradiated syngeneic (CBA, H-2^k) spleen cells pulsed with the cognate HY K^kSmcy (TENSGKDI) peptide. Graded doses of MSCs were added as third-party cells for the duration of the in vitro stimulation. After 24 hours CD8⁺ cells were analyzed for IFN-γ by intracellular staining (B). T-cell proliferation was assessed after 48 hours (A). Results are shown for cells cultured in the presence (▪) or absence () of the HY peptide. The results reported are the average of 3 experiments of identical design. T-cell proliferation cultures were performed in triplicate and results averaged. The bars show the SD. MSC/R indicates MSC-to-responder T cells ratio. Asterisk signifies statistically significant (at least P < .01) versus control cultures without MSCs in all experiments.