Rapid glycolytic metabolism underpins mucosal-associated invariant T cell functional responses to innate cytokines.

Mucosal-associated invariant T (MAIT) cells express a semi-invariant T cell receptor (TCR) that recognizes bacterial-derived antigens presented on MR1. Upon TCR triggering, MAIT cells respond rapidly, producing a range of effector molecules which facilitate host-protective responses in the context of microbial infections. In contrast, MAIT cell responses to viral infection are instead triggered by the recognition of cytokines, and occur independently of TCR engagement. The molecular and metabolic regulation of MAIT cell TCR responses is rapidly emerging, but there is a paucity of data on cytokine driven responses. Here, using high-resolution, quantitative proteomic analysis, we map the downstream proteome of innate cytokine (IL-18/IFNα)-activated MAIT cells, highlighting robust cytokine-driven remodeling and a signature that is distinct from the TCR-driven response. MAIT cells significantly increase protein biosynthesis in response to innate cytokine stimulation and rapidly upregulate the production of IFNγ, granzyme B, and IFN-stimulated gene 15. We demonstrate the metabolic kinetics of MAIT cell responses to cytokine stimulation and highlight a rapid but transient glycolytic burst that is uncoupled from mitochondrial remodeling and contrasts the robust metabolic profile elicited downstream of TCR engagement. Finally, we demonstrate differential contributions from both glycogen and glucose in supporting MAIT cell responses to innate cytokines and further highlight the importance of nutrient availability as a governing signal for MAIT cell fitness and effector functioning.