Fig. 5

Proliferation of CD4⁺ Treg in tolerated grafts requires functional PD-1 signaling. a Flow cytometric analysis and b quantification showing expression of PD-1 in CD4⁺hCD2⁻ (T_H) or CD4⁺hCD2⁺ (T_R) cells of rejecting and tolerated grafts, respectively. c A schematic diagram showing the protocol for antibody treatments. d H&E staining showing graft rejection following treatment with αPD-1 mAb in addition to coreceptor and costimulation blockade (3 mAb). Scale bars: 1000 μm. e Immunostaining and f quantifications of Ki67⁺FOXP3⁺ cells among total FOXP3⁺ cells in 3 mAb- and 3 mAb + αPD-1 mAb-treated grafts, respectively. Arrows indicate Ki67⁺FOXP3⁺ cells. Scale bars: 50 μm. *P < 0.05. (a–f) n = 5 per group