Effect of MSCs on allogeneic and syngeneic immune responses. (A) Two-way mixed lymphocyte reactions were performed with 105 C57BL/6 splenocytes and 105 BALB/c splenocytes in the presence or absence of 105 C57BL/6 naive or IFNγ-treated MSCs.After 3 days, supernatant was collected and tested for IFNγ release by ELISA. (B) DC2.4 cells (5 × 104 cells) were cocultured for 20 hours with ovalbumin-specific MHC class II-restricted T-T hybridomas (MF2.2D9; 105 cells) in the presence or not of 2.5 mg/mL soluble ovalbumin. Where indicated, 5 × 104 naive or IFNγ-pretreated (20 hours) MSCs from C57BL/6 or BALB/c mice were added to the cocultures. After 20 hours, supernatant was collected and tested for IL-2 release by ELISA. (C) Same as panel B, and where indicated, conditioned supernatant from naive or IFNγ-treated MSCs were added to the cocultures in replacement of MSCs. (D) Same as panel B, and where indicated, 5 × 104 naive or IFNγ-pretreated paraformaldehyde-fixed MSCs were added to the cocultures in the presence of ovalbumin (▪). Alternatively, DC2.4 cells were first pulsed with soluble ovalbumin for 20 hours and then cocultured with the indicated cells for another 20 hours (▤). Means of triplicates ± standard deviations of 1 of 2 representative experiments are shown.
