MIT researchers demonstrated that delivering mRNAs encoding key trophic factors to the liver transiently restored diverse naive and stem‑like T‑cell populations in aged mice, improving vaccine responses and cancer immunotherapy outcomes. The work uses lipid nanoparticles to repurpose the liver as a short‑term source of immune‑supporting signals. The team mapped thymic and peripheral T‑cell declines across ages, identified three replenishing factors (DLL1, FLT3L, IL‑7) and showed that hepatic expression boosts T‑cell diversity without clear autoimmunity signals in mice. Results were published in Nature and complement efforts to counter thymic involution. If translated to humans, hepatic mRNA reconstitution could offer a platform to enhance responses to vaccines and immunotherapies in older adults. Clinical translation will require rigorous safety assessment, dosing controls, and long‑term monitoring for immune dysregulation.