Researchers studying some of the world's oldest living people have identified a rare immune cell that multiplies dramatically with age, offering a possible clue to how a small number of people survive well past 100. The study, published in the journal Cell Reports and led by researchers including those at Keio University's Centre for Supercentenarian Medical Research in Tokyo, focused on cytotoxic CD4 T lymphocytes, a cell type that normally makes up a small share of the immune system's T cells.
The team profiled 43,584 individual T cells drawn from 28 people: eight adults aged 70 to 90, ten centenarians between 100 and 109, and ten supercentenarians who had reached at least 110. Cytotoxic CD4 cells accounted for roughly 4% of T cells in the youngest group, climbing to about 10% in centenarians and roughly 18% in supercentenarians, according to the findings reported by ScienceDaily.
Signs of a Long-Running Fight
What stood out to researchers was not just the volume of these cells but their uniformity. In the oldest participants, large clusters of nearly identical cells — in one case, more than half of a person's cytotoxic CD4 population — appeared to be clones descended from a single ancestor cell, evidence the immune system had mounted a sustained, repeated response to something specific. Some of the genetic sequences in those clones matched patterns previously seen in T cells that infiltrate tumors, particularly in lung cancer, according to coverage in Nature.
Researchers caution that the finding does not prove these cells are the reason some people live past 110, only that their presence correlates with extreme age. It remains possible that people who happen to carry more of these cells are simply more likely to survive long enough to become supercentenarians in the first place, rather than the cells actively extending life.
Supercentenarians remain exceedingly rare — only a few dozen are verified alive worldwide at any given time — which limits how large any study of them can be. The researchers say follow-up work will look at whether boosting or mimicking this cytotoxic CD4 response in younger patients could help fight cancer or chronic infection, independent of whether it turns out to extend lifespan on its own.
