IFNγ regulates the allostimulator activity of MSC. MLR with MSC stimulators, pretreated with IFNγ (A), or knockdown for IFNγ (B). (A) MSCs from 7 different donors were incubated with 100 U/mL IFNγ for 8 hours and then used as stimulators in MLR. MSCs from each donor were studied with PBMCs from 2 different donors. (B) MSCs from 5 different donors were stably knocked down for IFNγ using wild-type or mutant siRNA, then used as stimulators in MLR. Control MLR comprised untransfected MSCs or those stably transfected with vector alone (pPMSKH1). *P < .05 versus untreated MSCs. **P < .05 versus other experimental groups. Results are expressed as mean SI ± SE.