De novo synthesis and salvage pathway coordinately regulate polyamine homeostasis and determine T cell proliferation and function.

Robust and effective T cell-mediated immune responses require proper allocation of metabolic resources through metabolic pathways to sustain the energetically costly immune response. As an essential class of polycationic metabolites ubiquitously present in all living organisms, the polyamine pool is tightly regulated by biosynthesis and salvage pathway. We demonstrated that arginine is a major carbon donor and glutamine is a minor carbon donor for polyamine biosynthesis in T cells. Accordingly, the dependence of T cells can be partially relieved by replenishing the polyamine pool. In response to the blockage of biosynthesis, T cells can rapidly restore the polyamine pool through a compensatory increase in extracellular polyamine uptake, indicating a layer of metabolic plasticity. Simultaneously blocking synthesis and uptake depletes the intracellular polyamine pool, inhibits T cell proliferation, and suppresses T cell inflammation, indicating the potential therapeutic value of targeting the polyamine pool for managing inflammatory and autoimmune diseases.