Presentation of OVA peptides on both class I and class II MHC molecules by DCs phagocytized microencapsulated OVA. (A) Mitomycin C–treated DC2.4 cells (4 × 10⁴/well) were incubated with the indicated amount of soluble (▿) or microencapsulated OVA (○) for 2 hours, washed, and then cocultured for 4 hours with a T-cell hybridoma, B3Z cells (1 × 10⁵/well), which express β-galactosidase upon recognition of the OVA peptide, SIINFEKL, complexed with the H-2K^b molecule. The amount of β-galactosidase expressed in B3Z cells was determined by an enzymatic assay using chlorophenolred β-d-galactopyranoside as a substrate. Changes in optical density (OD) were measured at 580 nm. These results are representative of more than 10 experiments. (B) Mitomycin C–treated DCs (4 × 10⁴/well) generated from BM cells of Balb/c mice were incubated with OVA microspheres for 2 hours at 37°C, washed, and then CD4 T cells (1 × 10⁵/well) isolated from the spleens of DO11.10 mice were added. After a 48-hour incubation at 37°C, the culture supernatant was collected and assayed for IL-2 content using an IL-2 ELISA kit. These results are representative of more than 4 experiments. Each bar represents the mean ± SD of a triplicate experiment.