MSC inhibitory effect does not require APCs.

Proliferative response of B6 splenocytes (A) or HY-specific T-cell clone CTL-1025 (B) to CD3/CD28-coated beads in the presence or absence of MSCs. One representative experiment is shown of 3 performed. The background counts for unstimulated spleen and T-cell clone were less than 1% and less than 5%, respectively. The scale of the y-axis on the left and on the right is different. Asterisk indicates statistically significant (at least P < .01) versus control cultures without MSCs in all experiments.