MIT researchers showed that transient hepatic delivery of mRNAs encoding DLL1, FLT3L and IL‑7 via LNPs restored naive and stem‑like T‑cell populations in aged mice, boosting vaccine responses and improving outcomes in cancer immunotherapy models. The study, published in Nature, repurposes the liver as a source of immune‑supporting trophic factors to compensate for thymic involution. Treated aged mice exhibited expanded T‑cell diversity and enhanced responses to vaccination and checkpoint blockade without clear signs of autoimmunity in the preclinical window. The approach is mechanistically distinct from thymic regeneration strategies and suggests a potentially safer, transient therapeutic route using mRNA technology. Translational work must address dosing, durability, liver expression control, and safety in larger animals before human trials, but the data add a new modality to tackle immunosenescence and improve immunotherapy efficacy in older patients.