MSCs' immunomodulatory effects are mediated in vitro via secretion of PGE₂. Human MSCs and PBMCs from unrelated donors were cocultured in media containing PGE₂ inhibitors indomethacin (Indo) or NS-398 for 3 days in the presence of PHA (2.5 μg/mL). ³H-thymidine incorporation was measured as an indication of PBMC proliferation and data were presented as percent change in incorporated ³H-thymidine in presence or absence of inhibitors (hPBMCs stimulated with PHA in absence of MSCs = 100%). Bars represent percent change in ³H-thymidine (mean ± SD) from 3 independent experiments.