Science: People Who Live to 110 Have Unusual Immune Systems

Japanese researchers have identified an unusually high proportion of cytotoxic T cells in supercentenarians, which studies suggest could help protect the body against cancer and other threats associated with aging. The discovery provides new clues about the biological mechanisms that allow some people to reach extreme ages while maintaining relatively good health, according to a study published on the website cell.com.

• A rare population with a different immune system

People who reach the age of 110, called supercentenarians, are one of the rarest groups of people studied by researchers. Their exceptional longevity makes them an important model for understanding healthy aging. A new study by researchers at Osaka University and published in Cell Reports shows that the immune system of supercentenarians is not simply "aged", but appears to be undergoing a process of adaptation. The research team specifically looked at cytotoxic CD4 T cells, a rare category of immune cells capable of destroying other cells. The results show that these cells, known as CD4 CTL, begin to accumulate around the age of 100 and reach particularly high levels in people over 110. According to data presented in Nature, they represent about 4% of all T cells in younger adults, about 10% in centenarians and almost 18% in supercentenarians.

• Rare cells, with a role in the body's defense

CD4 cells are mainly known for their role in coordinating the immune response. In the case of cytotoxic CD4 cells, however, the function is different: they can attack and destroy target cells. The new study suggests that these cells have characteristics associated with responding to persistent threats. Some of the clones identified had T-cell receptors similar to those seen in cells that develop in the context of tumors, including lung cancer. The researchers believe that this peculiarity could contribute to the ability of supercentenarians to avoid or control certain age-related diseases. However, the researchers emphasize that there is no proof yet that these cells are the cause of longevity. The study shows an association between their accumulation and extreme old age, but the exact mechanism and their role in protecting the body require further research.

• The immune system never stops adapting

The discovery contradicts to some extent the simplified picture according to which aging would only involve a progressive degradation of the immune system.

A review published in Nature Reviews Immunology in April 2026 shows that centenarians and, in particular, supercentenarians sometimes have mechanisms by which immune function is maintained at unusually good levels. The researchers also identified features of inflammation, autophagy, and gene expression in immune cells that suggest a more efficient maintenance of immune balance. This perspective moves longevity research from the idea of simply "slowing down” aging to studying the mechanisms by which the body adapts over the course of a very long life.

• Longevity research, beyond records

The interest in supercentenarians is not limited to setting age records. These people offer researchers the opportunity to analyze how the body manages to delay the onset of diseases considered characteristic of aging. Previous studies by the Osaka team have already identified an unusual increase in cytotoxic CD4 cells in supercentenarians. The 2019 research, conducted on blood cells from seven supercentenarians and five younger people, showed a significant clonal expansion of these cells. The new study extends this observation and indicates that the expansion of CD4 CTL cells is not necessarily a phenomenon that occurs only at 110 years of age. The process seems to begin around the age of 100 and intensify thereafter.

• Possible implications for future medicine

The researchers hope that understanding the mechanisms by which supercentenarians maintain their immune defenses could eventually contribute to the development of medical strategies for healthy aging. One area of interest is the immune system's ability to identify and eliminate abnormal cells. If the mechanisms observed in supercentenarians can be understood and reproduced in other contexts, they could provide new leads for research into cancer, persistent infections, and diseases associated with aging. For now, however, the results should be viewed as biological clues, not as a definitive explanation of extreme longevity. Research suggests that the bodies of people who live to be over 110 do not give up their immune defenses, but rather seem to reorganize certain components to respond more effectively to the challenges accumulated throughout life.