Ablation of BATF Alleviates Transplant Rejection Abrogating the Effector Differentiation and Memory Responses of CD8 T Cells.

Allogeneic CD8 T cells are prominently involved in allograft rejection, but how their effector differentiation and function are regulated at a transcriptional level is not fully understood. Herein, we identified the basic leucine zipper ATF-like transcription factor (BATF) as a key transcription factor that drives the effector program of allogeneic CD8 T cells. We found that BATF is highly expressed in graft-infiltrating CD8 T cells, and its ablation in CD8 T cells significantly prolonged skin allograft survival in a fully MHC-mismatched transplantation model. To investigate how BATF dictates allogeneic CD8 T cell response, BATF and wild-type (WT) CD8 T cells were mixed in a 1:1 ratio and adoptively transferred into B6. mice 1 day prior to skin transplantation. Compared with WT CD8 T cells at the peak of rejection response, BATF CD8 T cells displayed a dysfunctional phenotype, evident by their failure to differentiate into CD127KLRG1 terminal effectors, impaired proliferative capacity and production of pro-inflammatory cytokines/cytotoxic molecules, and diminished capacity to infiltrate allografts. In association with the failure of effector differentiation, BATF CD8 T cells largely retained TCF1 expression and expressed significantly low levels of T-bet, TOX, and Ki67. At the memory phase, BATF-deficient CD8 T cells displayed impaired effector differentiation upon allogeneic antigen re-stimulation. Therefore, BATF is a critical transcriptional determinant that governs the terminal differentiation and memory responses of allogeneic CD8 T cells in the transplantation setting. Targeting BATF in CD8 T cells may be an attractive therapeutic approach to promote transplant acceptance.