Concentration-dependent inhibitory effect of cardiac mesenchymal stem cells (CMSCs) on concanavalin A-stimulated splenocytes. Mouse splenocytes (SCs) were incubated for 2 days with concanavalin A in the presence of different numbers of mitomycin-treated CMSCs (CMSC/SC ratios of 1:1, 1:10, and 1:100). Spleen cell proliferation was assessed on day 3 by pulsing with 3H-thymidine for 18 hours. Values represent the mean ± standard error of the mean from four independent experiments performed in triplicate. CPM = counts per minute. ** p < 0.01, *** p < 0.001.