Reduced T-cell proliferation by active β₂ integrins on DCs is not due to regulatory T-cell activity. (A) CD4⁺CD25⁺ T cells (C57BL/6; 1 × 10⁵/well) were cocultured with bmDCs from BALB/c mice at a T/DC ratio of 10:1. DCs were either pretreated with 100 ng/mL LPS for 24 hours or left untreated. Additionally, cocultures were treated with 5 mM Mg²⁺ where indicated. CD4⁺CD25⁻ T cells served as controls. After 3 days of culture, 1 μCi (0.037 MBq) ³H-thymidine was added for another 18 hours and proliferation was measured using a β-counter. (B) CD4⁺CD25⁻ T cells (1 × 10⁵) from C57BL/6 mice were coincubated with bmDCs from BALB/c mice at the indicated ratios, with or without addition of 5 mM Mg²⁺. Three days later, 1 μCi/well (0.037 MBq) ³H-thymidine was added for another 18 hours and thymidine incorporation was measured. Experiments were performed in triplicate; 1 representative experiment of 2 is shown. Error bars represent SEM of triplicates.