Figure 4.

PD-1 and PD-L1 expression in acute and chronic mouse colitis models and changes after treatment with TMSCs. In the acute colitis model, PD-1 levels were significantly increased compared to the normal and TMSC controls (all p < 0.001). However, PD-L1 levels did not change significantly. After treatment with TMSCs, PD-1 levels were significantly decreased (A) and PD-L1 levels were significantly increased compared to those in the colitis model (B). In the chronic colitis model, PD-1 levels increased compared to those of the normal and TMSC controls (C). By contrast, PD-L1 levels were decreased compared to the normal contorls (D). After treatment with TMSCs, PD-L1 levels were significantly increased (D) while PD-1 levels were decreased (C) in the chronic colitis model. PD-1, programmed death 1; PD-L1, programmed death-ligand 1; TMSC, tonsil-derived mesenchymal stem cell; DSS, dextran sulfate sodium; PBS, phosphate-buffered saline.