Interestingly, PD1+CD8+CD45RA+CCR7+ T cells exhibited features of both CD8+ Treg and CD8+ Teff and expressed TSCM makers, including CXCR3, CD95 and CD69 as well as CD49d, CD107a, perforin, granzyme B, IFN-γ and IL-2, and CD103, CD73 which are also expressed in CD8+ Treg that alleviate GVHD.59,79,80 We further confirmed these findings in clinical donors by functional experiments in vitro, which demonstrated this donor-derived T cell subset mobilized by G-CSF had a dual function of immune regulation and cytotoxicity. Here, GZMB is linked to graft versus host disease.