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

Splenocytes from normal, nontransgenic female C57BL/6 (H-2^b) mice immunized with syngeneic male spleen cells were restimulated in vitro with syngeneic male spleen cells. Graded doses of MSCs were added as a third party to the MLRs. After 7 days, the cells were harvested and restimulated with female spleen cells pulsed with the HY peptides HY D^bSmcy (KCSRNRQYL), HY D^bUty (WMHHNMDLI), and HY A^bDby (NAGFNSNRANSSRSS) and then assessed for T-cell proliferation (A), numbers of HY-specific IFN-γ⁺cells (B), and HY D^bSmcy and HY D^bUty tetramer-positive CD8⁺ T cells (C). HY-specific cytotoxic activity was tested against HY peptide-pulsed (HY D^bSmcy and HY D^bUty) RMA-S cell line in a⁵¹Cr-release assay (D). The results refer to the cultures in the presence (▪) or absence () of the HY peptide. The results reported are the average of 5 experiments of identical design. T-cell proliferations (2 experiments) were performed in triplicate and results averaged. The bars show the SD. MSC/R indicates the MSC-to-responder T cells ratio. * signifies statistically significant (at least P < .01) versus control cultures without MSCs in all experiments.