MSC-mediated inhibition of IFN-γ production is reversible. C6 splenocytes (5 × 10⁶) were stimulated with syngeneic K^kSmcy HY peptide (TENSGKDI)–pulsed syngeneic female spleen cells (5 × 10⁶) in the absence (A) or presence (B) of MSCs (1 × 10⁵). An aliquot of the cultures (▪) was harvested after 24 hours and was directly evaluated for the number of IFN-γ⁺/CD8⁺ T cells, as per control. Another aliquot (□) was harvested at the same time, washed, and restimulated with the cognate peptide for another 24 hours. A third aliquot (▨) remained in culture for a total duration of 48 hours and then was harvested, washed, and restimulated for 24 hours before the enumeration of IFN-γ⁺/CD8⁺ T cells. T-cell cultures containing restimulated MSCs (B, □ and ▨) underwent immunomagnetic depletion with CD106 to remove MSCs before restimulation. Results are the average of 3 experiments of identical design; bars show the standard deviation (SD). ^*Statistically significant (P < .01).