OVA-incorporated BMMCs induce T-cell proliferation in vitro and in vivo. (A) MHC class II^−/− BMMCs were pretreated with (bottom) or without (top) anti-OVA IgE, washed, and incubated with OVA (0.5 μg/mL) for 2 days. The BMMCs were then washed and cocultured with CFSE-labeled OT-II splenocytes. (B) 3 × 10⁶ CFSE-labeled CD4⁺ T cells from OT-II.SJL mice were injected intravenously into wild-type B6 mice. MHC class II^−/− BMMCs were anti-OVA IgE pretreated and incubated with (right) or without (left) OVA (50 μg/mL) for 48 hours and injected intravenously into mice 1 day after T-cell transfer. Five days later, the spleen (top) and inguinal lymph nodes (LN; bottom) of mice previously injected with intravenous or subcutaneous BMMCs, respectively, were harvested, and CFSE dilution of transferred CD4⁺ T cells was analyzed by flow cytometry. The cells represented in the histograms are gated on CD45.1⁺CD4⁺ T cells.