Cedars-Sinai researchers reported in Cell Metabolism that PD-L2 can function as an immune checkpoint on senescent cells, enabling them to evade clearance and accumulate during aging. The team found higher PD-L2 in isolated senescent human cells and observed age-related increases in circulating soluble PD-L2. In older mice lacking PD-L2, investigators reported fewer accumulated senescent cells along with improved insulin sensitivity and grip strength. In aged wild-type animals, anti-PD-L2 therapy restored insulin sensitivity and increased physical strength, linking the checkpoint to metabolic and functional outcomes. The findings broaden PD-L2’s scope beyond cancer immune evasion into aging biology, where persistent senescent cells contribute to tissue dysfunction. The study also suggests PD-L2 could serve as a blood marker for tracking senescent cell burden. Taken together, the work highlights checkpoint mechanisms as actionable levers not only for tumors, but also for systemic aging-related disease pathways.