MIT researchers demonstrated that delivering mRNAs encoding trophic factors (DLL1, FLT3L, IL‑7) to hepatocytes can transiently restore thymic‑like support and enlarge the naive T‑cell pool in aged mice, improving vaccine responses and cancer immunotherapy outcomes. The team published the work in Nature and reported no immediate signs of autoimmunity or toxicity in preclinical models. The approach repurposes the liver as a programmable secretory organ to supply immune‑supporting cytokines that decline with age, sidestepping direct thymic regeneration. Translational steps will need to address dosing, durability, and safety before human trials can be contemplated.