Cross-presentation by pDCs is inducible. (A-D) Various concentrations of purified cDCs (left panels) or pDCs (right panels) were cultured for 24 hours with 10⁵ OVA-specific B3Z cells. (A,B) Cells were incubated in the presence of: (A) culture medium alone (○, CM), OVA (●, 3 mg/mL), OVA_257-264 peptide ( pOVA, 1 μg/mL), (B) control beads (◇, 10⁷/mL) or beads-OVA_257-264 (♦, 10⁷/mL). (C,D) Cells were incubated in the presence of OVA (3 mg/mL; C, main graph), OVA_257-264 peptide (1 μg/mL; C, inset) or beads-OVA_257-264 (10⁷/mL, D) and culture medium alone (○, CM), R848 (●, 1 μg/mL), or CpG (■, 10 μg/mL). (E) 10⁴-purified pDCs from TAP^−/− or WT mice were incubated in the presence of serial dilution of OVA_257-264 peptide (left), OVA alone (middle), or OVA and R848 (right) and 10⁵ B3Z for 24 hours. Stimulation of B3Z was measured as the release of IL-2 into supernatants as assayed by CTLL-2 proliferation monitored by ³H-labeled thymidine incorporation. Results are expressed as mean cpm plus or minus SD for duplicate wells and are representative of 3 experiments.