FIGURE 2.

Topical calcipotriol followed by TCI induces Ag-specific CD4⁺CD25⁺ Treg. A, The fraction of CD25⁺ T cells among CD4⁺ T cells in the skin-draining LN was determined after three daily applications of calcipotriol, followed by OVA immunization (n = 6/group). B, Effect of CD4⁺ T cell subsets transferred from calcipotriol-treated mice upon CD8⁺ T cell priming responses in previously naive mice. CD4⁺CD25⁺ T cells or CD4⁺CD25⁻ T cells from calcipotriol-treated and OVA-immunized donors were purified from peripheral LN and spleen 4 days after immunization and were transferred into recipients along with OT-1 CD8⁺ T cells (as depicted in E). Recipients were next immunized with OVA/CpG. CD4⁺ CD25⁺ T cells from calcipotriol and OVA-immunized mice suppressed proliferation of OT-I cells (n = 6/group; ordinate shows percentage control response). C, Ag specificity of CD4⁺CD25⁺ cells. No inhibition of CD8⁺ T cell proliferation or IFN-γ production was noted when 2 × 10⁶ purified CD4⁺CD25⁺ T cells from mice treated with calcipotriol and immunized with BSA were transferred (n = 4). D, Calcipotriol-induced Treg efficiently prevented OT-I cell proliferation in vivo. As few as 5 × 10⁴ cells were sufficient to suppress the proliferation of 5 × 10⁶ adoptively transferred OT-I cells.