The TET2 methylcytosine dioxygenase regulates early and late transitions in exhausted CD8+ T-cell differentiation

Epigenetic reprogramming of CAR T-cells by targeting TET2, a methylcytosine deoxygenase that mediates active DNA demethylation, has shown therapeutic potential; however, the role of TET2 in TEX development is unclear. In both CAR T-cell exhaustion models in vitro and chronic LCMV infection in vivo, TET2 drove the conversion from memory-like, self-renewing TEX progenitors towards effector (TEFF)-like and terminally differentiated TEX. TET2-deficient terminally differentiated TEX retained aspects of TEX progenitor biology, including decreased expression of the transcription factor TOX, suggesting that TET2 is required for terminal exhaustion. Overall design: Mice with chronic LCMV infection received WT or TET2KO P14 T cells. Naive and D15 T cells were isolated; D15 T cells were assessed in bulk, as well as in sorted subsets of Ly108+ and Ly108-. Bulk RNA-Seq and ATAC Seq were performed. Separately, human CAR T cells targeting CD19 were co-cultured with irradiated K562-CD19+ cells at a 1:1 ratio for 5 days, with fresh R10 media and newly irradiated K562 cells for 4-5 additional stimulations. Bulk RNA-Seq was performed.