MHC class II molecule acquisition is marked enhanced by T-cell activation.

DO11.10 CD4⁺ T cells were cocultured overnight with bone marrow–derived BALB/c DCs or CBA DCs either without peptide, with 10 μg/mL OVA_323-339 peptide, or 1 μg/mL soluble anti-CD3. Cells were then harvested and stained with PE-conjugated anti–H2-A^d or anti–H2-A^k, and FITC-conjugated anti-CD4 (bold lines). The levels of H2-A^d and H2-A^k on DO11.10 CD4⁺ cells were analyzed by flow cytometry. Only the CD4⁺ population was gated for analysis. (DO11.10 CD4⁺ T cells in medium control [shaded areas] for H2-A^d staining: MFI = 10.64; % in M1 gate = 1.66%; H2-A^k staining: MFI = 18.76; % in M1 gate = 3.22%.)