Fig. 4.

IFN-I produced by activated CD4⁺ T cells is important for the cDC1-mediated CTL response to cell-associated tumor antigens. A tumor antigen-specific CTL priming system [6] was used to investigate the impact of IFN-I produced by activated CD4⁺ T cells on the cross-presentation and cross-priming abilities of cDC1s. IFNβ expression was downregulated in CD4⁺ T cells by siRNA. A Flow cytometry histograms depicting intracellular IFNβ expression and the surface expression of the indicated markers identifying effector T cells under the indicated conditions. B MFI values for intracellular IFNβ expression under the indicated conditions. C Schematic illustration of the tumor antigen-specific CTL priming system. D CD8⁺ T-cell proliferation induced by MART-1_15–40 long peptide (LP) based on CTV dilution. E Percentages of MART-1_26–35/HLA-A2-specific (tet^postive) cells among CD8⁺ T cells or CTV^negative CD8⁺ T cells in the MART-1_15-40 LP setting. F CTL response to MART-1_15–40 LP based on intracellular Granzyme B staining. G Percentages of Granzyme B⁺ cells among CTV^negative CD8⁺ T cells and MFI values of Granzyme B in the MART-1_15-40 LP setting. H CD8⁺ T-cell proliferation in response to dead Mel526 cell debris based on CTV dilution. I Percentages of MART-1_26-35/HLA-A2-specific (tet^positive) cells and tet^negative cells among CTV^negative CD8⁺ T cells in the dead Mel526 cell debris setting. J CTL response to dead Mel526 cell debris based on intracellular Granzyme B staining. K Percentages of Granzyme B⁺ cells among CTV^negative CD8⁺ T cells and MFI values of Granzyme B in the dead Mel526 cell debris setting. The data were pooled from eight (n = 8 in B), seven (n = 7 in E, G) or five (n = 5 in I, K) independent experiments. P < 0.05*, P < 0.01**, P < 0.001***, P < 0.0001**** (one-way ANOVA). The data are shown as the means ± SEMs