MSCs do not stimulate allogeneic T cells.

The ability of MSCs to function as APCs was tested by using MSCs as stimulators of secondary allogeneic MLRs. Spleen cells from CBA (H2^k) mice, stimulated in primary cultures with BALB.B (H2^b) spleen cells (2 × 10⁵/well), were restimulated with (A) BALB.B or (B) autologous CBA splenocytes as stimulators in the control cultures and with (C) graded numbers (10², 10³, 10⁴/well) of irradiated (60 cGy; black bars) or nonirradiated (white bars) MSCs of BALB.B origin. (D) In a separate experiment, BALB.B MSCs were pretreated with IFN-γ (100 U/mL for 48 hours) before being used in the cultures. (E) Proliferation of MSCs alone not irradiated. Cultures were performed in triplicate and the results reported are the average of 3 experiments of identical design. The bars show the SD. * indicates statistically significant (at least P < .01) versus control cultures (stimulation with syngeneic spleen cells) in all experiments.