FAS-controlled T cells drive lymphoproliferation through glycolysis without effector differentiation.

Lymphoproliferation in autoimmune lymphoproliferative syndrome (ALPS) due to FAS deficiency is driven by highly proliferative FAS-controlled T cells (FCT) with a distinct molecular signature. Activating signals and metabolic fuels of their proliferation are poorly understood. Lymphoproliferation caused by proliferative T cells is also a hallmark of acute EBV infection. In these antiviral T cells, a metabolic switch to glycolysis underpins effector differentiation and IFNγ translation. Here, we used EBV-induced CD8 effector T cells as a benchmark to characterize FCT metabolism. Metabolic assays, RNA sequencing, and in silico computational analysis revealed that FCT are as highly glycolytic as EBV-induced effector T cells, but this metabolic program is uncoupled from T-BET expression and IFNγ production. In contrast to virus-activated T cells, FCT showed mitochondrial hyperpolarization and elevated reactive oxygen species production. These findings support a model of FCT lymphoproliferation, in which activating signals strongly enhance glycolysis but do not induce classical effector differentiation.