Figure 2. PD-1 expression on CD8⁺ T cells is critical to induce tolerance after lung transplantation.

(A) Representative contour plot depicting PD-L1 expression on CD11c⁺ antigen presenting cells and PD-1 expression on CD8⁺ T cells within BALB/c lung allografts seven days after transplantation into immunosuppressed B6 recipients. (B) Representative histology, (C) numerical ISHLT rejection grades, (D) intragraft CD8⁺/CD4⁺ T cell ratio of native (CD45.1⁺) recipient CD8⁺ T lymphocytes and (E) proliferative responses of adoptively transferred (CD45.2⁺) as well as native (CD45.1⁺) T cells within BALB/c lung allografts seven days after transplantation into immunosuppressed B6 CD45.1⁺ recipients that received either wildtype or PD-1 deficient B6 CD45.2⁺ CD8⁺ T lymphocytes at the time of transplantation. Data represent mean ± SEM. *p<0.05, **p<0.01, ***p<0.001 by unpaired T test. Representative contour plots and graphic representation of relative abundance of naïve (CD62L^hiCD44^low), central memory (CM) (CD62L^hiCD44^hi) and effector memory (EM) (CD62L^lowCD44^hi) for (F) native CD45.1⁺ CD4⁺ and CD8⁺ T cells and for (G) adoptively transferred wildtype and PD-1-deficient B6 CD45.2⁺ CD8⁺ T cells in BALB/c lung allografts seven days after transplantation into immunosuppressed B6 recipients. Data represent mean ± SEM. *p < 0.05, **p < 0.01 by Mann-Whitney U test.