Donor CD4+ and CD8+ T cells from the liver and gut tissues of GVHD recipients given STAT3–/– T cells or STAT3–/–PD-1–/– T cells showed similarly low TCRB and TCRA diversity and no statistically significant differences as compared with CD4+ and CD8+ T cells from recipients given WT donor T cells (Figure 5, A and B, and Supplemental Figure 4, A and B). Here, PDCD1 is linked to graft versus host disease.