Single-cell metabolic analysis by mass cytometry reveals distinct transitional states of CD8 T cell differentiation

Mass cytometry permits high-dimensional analysis of diverse aspects of cellular behavior. Here, we adapted this platform to simultaneously profile metabolism, signaling, cell cycle, and effector function with single-cell resolution. Using this approach, we measured enzymes characterizing glycolysis, the TCA cycle, fatty acid oxidation, oxidative phosphorylation, and nutrient transport. In conjunction, we measured downstream targets of TCR signaling regulating translation, proliferation and cytotoxicity as well as surface markers and transcription factors delineating CD8 T cell differentiation. High-dimensional single-cell metabolic analysis by mass cytometry permits identification of unique metabolic and differentiation states of extremely rare cell populations, such as antigen-specific T cells. We interrogated antigen-specific CD8 T cell activation in vitro as well as the trajectory of CD8 T cells responding to Listeria monocytogenes infection, a well-characterized model for studies of T cell differentiation. This integrated, high- dimensional approach revealed a novel, activated, and highly metabolically active transitional T cell subset emerging at four days post-infection. These cells simultaneously exhibit glycolytic and oxidative functional programs, which we propose represents a key metabolic inflection point in CD8+ T cell differentiation. This approach should be useful for mechanistic investigations of metabolic regulation of immune responses in vivo.