Fig. 4.

Immunosuppressive and immunogenic effects of BM-MSCs on T lymphocytes. A Representative gating strategy for flow cytometric analysis of T lymphocyte proliferation. B Immunosuppressive effects were assessed for each BM-MSC preparation on stimulated T lymphocytes isolated from the peripheral blood of three independent donors. BM-MSCs exerted significant immunosuppressive effects on stimulated T lymphocytes at a MSC:PBMC ratio of 1:5, and the size of these effects varied between culture conditions. No significant immunosuppressive effects were observed at higher ratios (data not shown). Results were expressed as the percentage proliferation relative to a CD3/CD28 stimulated T lymphocyte control averaged across the three blood donors. Bar graphs represent the mean ± SD of three biological replicates (n = 3) for each culture media condition (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001). C To assess potential immunogenic effects, percentage proliferation of unstimulated T lymphocytes co-cultured with BM-MSCs at a MSC:PBMC ratio of 1:5 for 4 days. Co-culture with BM-MSCs isolated and expanded in any media condition did not significantly increase T lymphocyte proliferation compared to unstimulated controls (grey bar). Results for each BM-MSC preparation were averaged across three blood donors. Bar graphs represent the mean ± SD of three biological replicates (n = 3) for each culture media condition