The MSC inhibitory effect is MHC-independent.

Spleen cells from C6 transgenic (naive) (A) or normal C57BL/6 HY-immune (memory) (B) mice were stimulated with HY K^kSmcy peptide or syngeneic male cells, respectively, as described previously, in the presence or absence of the 3T3-F442A MSC line, which does not express MHC class I molecules even after IFN-γ treatment. T-cell proliferation (cpm) and percentage of IFN-γ–producing CD8⁺ T cells were evaluated. The results refer to the cultures in the presence (■) or absence (▪) of HY antigen. The results reported are the average of 3 experiments of identical design. T-cell proliferation cultures were performed in triplicate and results averaged. The bars show the SD. * indicates statistically significant (at least P < .01) versus control cultures without MSC in all experiments.