MSCs preferentially inhibit the production of perforin from NK cells. Spleen DX5⁺ NK cells were cocultured with spleen MSCs for 5 days at the ratio of 1:1 (A) or at varying ratios as indicated in panel B. DX5⁺ NK cells were then isolated with DX5 antibody-coated magnetic beads using the method as described previously. NK cells (1 × 10⁶) were lysed in protein lysis buffer, and 50 μg total protein from each lysate was resolved on a 10% SDS PAGE gel. The proteins were then transferred to a nitrocellulose membrane, and the blots were probed with the indicated antibodies. The data are representative of 3 independent experiments. β-actin served as an internal control to confirm equivalent protein loading.