Tet2 deletion in CD4+ T cells disrupts Th1 lineage commitment in memory cells and enhances T follicular helper cell recall responses

Following viral clearance, antigen-specific CD4+ T cells contract and form a pool of distinct Th1 and Tfh memory cells that possess unique epigenetic programs, allowing them to rapidly recall their specific effector functions upon rechallenge. DNA methylation programing mediated by the methylcytosine dioxygenase Tet2 contributes to balancing Th1 and Tfh cell differentiation during acute viral infection, however the role of Tet2 in CD4+ T cell memory formation and recall is unclear. Using adoptive transfer models of antigen-specific WT andTet2KO CD4+ T cells, we find that Tet2 is required for full commitment of CD4+ T cells to the Th1 lineage and that in the absence of Tet2, memory cells preferentially recall a Tfh like phenotype with enhanced expansion upon secondary challenge. These findings demonstrate an important role for Tet2 in enforcing lineage commitment and programing proliferation potential, and highlight the potential of targeting epigenetic programing to enhance adaptive immune responses. Overall design: To determine the role of TET2 in the memory T cell recall response, we performed whole genome enzymatic methylation sequencing of either WT or Tet2 KO secondary effector cells 7 days post LCMV rechallenge and then sorted into secondary Tfh (CXCR5+) and Th1 (CXCR5-) effector subsets.