MSC-mediated activation of primary OT-II CD4+ T cells. (A) C57BL/6 MSCs or DC2.4 were pretreated with recombinant mouse IFNγ (50 ng/mL) and soluble ovalbumin (2.5 mg/mL) for 20 hours and then cocultured (5 × 104 cells) for 48 hours with ovalbumin-specific purified CD4+ T splenocytes (105 cells; > 80% purity) from OT-II transgeneic mice. Where indicated, MSCs and DC2.4 were first incubated with a blocking antibody to mouse CD80 or an isotypic control 30 minutes prior to and during coculture. After coculture, supernatant was collected and tested for IL-2 release by ELISA. Means of triplicates ± standard deviations of 1 of 2 representative experiments are shown. (B) C57BL/6 MSCs were analyzed by flow cytometry for B7-H1 surface expression before and after recombinant IFNγ treatment (50 ng/mL for 20 hours). Plots show isotype control IgG staining profile (broken line) versus specific Ab staining profile (solid line).
