A summary of immunological signals for the regulation of lipid metabolism in T cells. a, Upon TCR engagement, T cells activates PI3K–Akt and mTOR signaling to induce FA synthesis and mevalonate metabolism. b, CD28 costimulation induces transient expression of CPT1a through thioredoxin-interacting protein (TXNIP) and miR33 (before first cell division), and may enhance mevalonate and lipid synthesis by boosting TCR-dependent mTORC1 activation. c, The cytokines IL-15 and IL-7 induce FAO, in part by enhancing expression of CPT1a and mediating glycerol uptake via aquaporin-9, respectively, to maintain mitochondrial respiration.