Capacity of OCs to present soluble antigen TT to CD4⁺ T cells and induce T-cell proliferation. (A) Proliferation of tetanus toxoid (TT)–specific T cells induced by TT-pulsed OCs and DCs. CFSE-labeled CD4⁺ T cells were cultured with autologous OCs or DCs pulsed with TT for 6 days. Flow cytometric analysis was performed to detect the proliferation of CD4⁺ T cells. Representative results from 1 of 3 experiments performed are shown. (B) MHC restriction in TT-specific CD4⁺ T-cell response. Antibody (10 μg/mL) for HLA-DR or isotypic control was added to the culture of T cells and TT-pulsed OCs. Data show the proliferation rate of CD4⁺ T cells detected by CFSE dilution assay. (C) Effect of chloroquine on antigen processing and presentation by OCs. Chloroquine was added at a final concentration of 50 mM to the cell cultures, and T-cell proliferation was detected by CFSE dilution assay. Cultures in panels B and C were run in triplicate and results are expressed as mean ± SD. Representative results from 2 independent experiments are shown.