Figure 4. Antigen transfer from injected DC to host DC occurs at the site of DC injection.

(A) C57BL/6 mice were injected with CD45.1⁺ WT DC or CD45.1⁺ WT DC loaded with OVA protein (2 mg/ml). The dLN were collected 24 h later, and the CD8⁺ DC, the CD8⁻CD205⁺ skin-derived DC and the CD8⁻CD205⁻ double negative DC populations were sorted and cultured in duplicate with CFSE-labelled, purified OT-I or OT-II T for 3 days or 5 days, respectively. OVA-specific proliferation was evaluated as CFSE dilution by flow cytometry. Each symbol represents the mean+SEM of the percentage of divided cells/well. Combined data from two independent experiments that gave similar results are shown. (B) C57BL/6 were injected with CFSE-labelled CD45-congenic OT-II CD4⁺ T cells and immunized 24 h later with WT or MHCII^−/− DC that had been loaded with OVA protein (2 mg/ml), and treated with Ptx or left untreated. CD4⁺ T cell proliferation in dLN was determined by flow cytometry 3 days after DC immunization. Representative flow cytometry histograms of CD45.1⁺CD4⁺ T cells from individual dLN are shown on the left. The mean ± SEM of the percent divided cells in each group is shown. The bar graph on the right shows mean+SEM of the number of divided CD45.1⁺CD4⁺ T cells/dLN. Combined results from two independent experiments each with 5 mice per group are shown.