The inhibitory effect of MSCs requires cell contact.

HY-specific memory T cells from immunized B6 females were stimulated in vitro with syngeneic male spleen cells (B6) in the presence of MSCs (B6 + MSC) or supernatant from MSC cultures (B6 + MSC-SN). In parallel, responder T cells were also stimulated with syngeneic male spleen cells in the presence of MSCs in a Transwell system (B6 + MSC-T/W). The percentage of HYD^bSmcy and HYD^bUty tetramer-positive CD8⁺ T cells (A) and HY-specific IFN-γ⁺ CD8⁺ T cells (B) are shown for each culture. The results reported are the average of 4 identical experiments. The bars show the SD. * indicates statistically significant (at least P < .01) versus control cultures (B6).