Fig. 6: PD-1 ligation downmodulates asparaginyl endopeptidase (AEP) and stabilizes the expression of FOXP3 and AREG.

CD4⁺ T cells were stimulated as in Fig. 5. A, B AEP, pAEP, FOXP3, BCL-2, and Ki-67 staining in PD-1^highFOXP3⁺ (blue) and PD-1^lowFOXP3⁺ cells 6 days post-infection. Some CD4⁺ T cells stimulated and infected as above were moved to a plate coated with recombinant human PD-L1/B7-H1 Fc chimera (5 μg/ml) or treated with AEP inhibitor (10 μM) 36 h after infection. Percentage of FOXP3⁺ cells in CD4⁺ population and FOXP3 MFI on FOXP3⁺ gated cells (C), percentage and absolute cell numbers of PD-1^hiIFN-γ⁺ cells in FOXP3⁺ population (D), and AREG expression in FOXP3⁺ cells (E), as determined by flow cytometric analyses. Results represent triplicate experiments with similar results and are presented as mean value +/− SEM (ordinary one-way ANOVA and multiple t tests were conducted; *P < 0.05; **<0.005, ***<0.0005).