Effect of inhibitors and T-cell suppression by MSCs from iNOS^−/− mice. (A) L-NAME and indomethacin (INDO) restored T-cell proliferation, but TGF-β antibody and 1-MT had no effect. Splenocytes (1 × 10⁵) were activated with Con A in the presence or absence of irradiated MSCs (2.5 × 10³), 1 mM L-NAME, 5 μM indomethacin,¹⁴  1 μg/mL or 10 μg/mL TGF-β antibody, and 1 mM 1-MT for 48 hours. The incorporation of [³H]-thymidine is shown relative to that in the absence of MSCs. Shown is the mean ± SD of 3 independent experiments. *P < .05. NS indicates P > .05. (B) MSCs from iNOS^−/− mice have a reduced ability to inhibit T-cell proliferation. Splenocytes (1 × 10⁵) were activated with Con A in the presence or absence of MSCs (2.5 × 10³) from either wild-type or iNOS^−/− mice. Left panel, incorporation of [³H]-thymidine relative to that in the absence of MSCs. Right panel, production of NO. The values are the means ± SD from 3 independent experiments. *P < .05.