MIT researchers delivered an mRNA cocktail (DLL1, FLT3L, IL‑7) to hepatocytes using lipid nanoparticles to transiently reconstitute trophic signaling and restore T‑cell diversity in aged mice. The Nature‑published work showed improved vaccine responses and stronger outcomes from cancer immunotherapy without overt toxicity in the models. The approach sidesteps direct thymic regeneration by repurposing the liver as a temporary source of immune‑supporting factors, compensating for age‑related thymic involution that narrows the T‑cell repertoire. Treated older animals mounted larger, more diverse T‑cell responses and showed enhanced tumor control when combined with checkpoint blockade. If translated, the platform could become an adjunct to vaccines and immuno‑oncology in older populations; however, human safety, dosing windows and durability of effect will determine clinical viability.