MAPCs potently inhibit allogeneic T-cell proliferation and activation. (A) MLR was performed by mixing B6-purified T cells with irradiated BALB/c stimulators (1:1) and B6 MAPCs (1:10, 1:100). These cultures were pulsed with ³H-thymidine on the indicated days and harvested 16 hours later. Proliferation was determined as a measure of radioactive uptake. MLR reaction was performed as above using BALB/c T cells plus B6 stimulators and BALB/c MAPCs (B), or BALB/c T cells plus B10.Br stimulators and B6 MAPCs (C). FACS analysis of B6 > BALB/c MLR plus B6 MAPCs was performed on the indicated days and gated on CD4⁺ T cells (D) or CD8⁺ T cells (E) in conjunction with activation markers.