In vivo metabolite tracing of T cells

T cells are integral players in the adaptive immune system that readily adapt their metabolism to meet their energetic and biosynthetic needs. A major hurdle to understand physiologic T cell metabolism has been the differences between in vitro cell culture conditions and the complex in vivo milieu. To address this, we have developed a protocol that merges traditional immunology infection models with whole-body metabolite infusion and mass spectrometry (MS)-based metabolomic profiling to assess T cell metabolism in vivo. In this protocol, pathogen-infected mice are infused via the tail vein with an isotopically labeled metabolite, followed by rapid magnetic bead isolation to purify T cell populations and then stable isotope labeling (SIL) analysis conducted by MS. This procedure enables researchers to evaluate metabolic substrate utilization by specific T cell subpopulations in the context of physiological immune responses in vivo.