DC-instructed MCs efficiently induce ex vivo allogeneic T cell priming. (A) SJL/J^B6 chimera were generated by lethal irradiation of SJL/J recipient mice and transfer of BM cells from C57/BL6 donor mice. DC-to-MC communication was induced by DNFB administration onto ear skin of SJL/JB6 chimera mice or control SJL/J mice, and DCs and MCs were sorted from ear skin 24 h after DNFB. CFSE-labeled SJL/J T cells were cocultured with DCs (CD45.2⁺CD11c⁺H2b⁺) and MCs (CD45.1⁺c-kit⁺FcεRI⁺) sorted from ear skin of SJL/J^B6 chimera mice (n = 9) or SJL/J control mice (n = 6) 24 h after DNFB, or C57BL/6 spleen DCs (n = 6) as positive control. (B and C) T cell proliferation was assessed as CFSE dilution (B) and quantified as proliferated T cell fraction from total T cells and as mean fluorescence intensity (MFI; C). (D) The proliferated T cell fraction was plotted versus the H2^b-expressing MC fraction to assess parameter correlation. (E) Cytokines released upon SJL/J T cell co-culture with DCs and MCs were quantified in the co-culture supernatant by bead-based multiplex assay. *, P < 0.05; **, P < 0.01; ***, P < 0.001.