Allogeneic MSCs trigger the onset of a memory T-cell response. (A-B) B6 mice were infused with PBS, BALB/b splenocytes (0.5 × 10⁶), BALB/b MSCs (0.5 × 10⁶), or B6 MSCs (0.5 × 10⁶). (C) BALB/c mice were infused with PBS, B6 splenocytes (0.5 × 10⁶), B6 MSCs (0.5 × 10⁶), or BALB/c MSCs (0.5 × 10⁶). (D) Balb/c mice were injected with PBS, C³H splenocytes (0.5 × 10⁶), BALB/c MSCs (0.5 × 10⁶), or C³H MSCs (0.5 × 10⁶). After 4 weeks, in vivo cytotoxicity assay was performed and peripheral blood was harvested after 1 and 3 days (A-B) or after 3 hours and 1 day (C-D). Representative dot plots are displayed (A). Results are expressed as the mean survival (± SD) of allogeneic donor cells of 2 independent experiments (B-D). *P < .05; **P < .001; ***P < .001 compared with syngeneic MSCs.