Mitochondrial stress induced by continuous stimulation under hypoxia rapidly drives T cell exhaustion.

Abstract

Cancer and chronic infections induce T cell exhaustion, a hypofunctional fate carrying distinct epigenetic, transcriptomic, and metabolic characteristics. However, drivers of exhaustion remain poorly understood. As intratumoral exhausted T cells experience severe hypoxia, we hypothesized metabolic stress alters their responses to other signals, specifically persistent antigenic stimulation. In vitro, while CD8+ T cells experiencing continuous stimulation or hypoxia alone differentiate into functional effectors, the combination rapidly drove T cell dysfunction consistent with exhaustion. Continuous stimulation promoted Blimp-1-mediated repression of PGC1α-dependent mitochondrial reprogramming, rendering cells poorly responsive to hypoxia. Loss of mitochondrial function generated intolerable levels of ROS, sufficient to promote exhausted-like states, in part through phosphatase inhibition and consequent NFAT activity. Reducing T cell-intrinsic ROS and lowering tumor hypoxia limited T cell exhaustion, synergizing with immunotherapy. Thus, immunologic and metabolic signaling are intrinsically linked: through mitigation of metabolic stress, T cell differentiation can be altered to promote more functional cellular fates.