Pyrimidine de novo synthesis inhibition selectively blocks effector but not memory T-cell development [bulk RNA-seq]

Blocking pyrimidine de novo synthesis via inhibiting Dihydroorotate dehydrogenase (DHODH) is clinically used to treat autoimmunity and to prevent the growth of rapidly dividing cells including activated T-cells. We identified a previously unrecognized resistance of precursors of memory T-cells to pyrimidine starvation. While the treatment effectively blocks effector T-cells, numbers, function and transcriptional profiles of memory T-cells and their precursors remain completely unaltered. We pinpoint this effect to a narrow time-window in the early T-cell expansion phase, when developing effector, but not memory T-cells are selectively vulnerable to pyrimidine starvation. This stems from a higher proliferative pace of early effector T-cells paired with lower pyrimidine synthesis capacity compared to memory precursors. This differential sensitivity constitutes a novel, drug-targetable checkpoint that efficiently diminishes effector T-cells without harming the memory compartment. We envision that knowledge of this pyrimidine synthesis-based cell fate-determining particularity opens up new means to safely manipulate effector T-cell responses. Transferred OT-1 T-cells were isolated from host mice treated with Leflunomide or control on day 7 and day 28 post infection with OVA-expressing Listeria monocytogenes (n=5).