People who live past 110 have an unusual abundance of killer immune cells

Supercentenarians, individuals who live past the age of 110, have been found to possess a higher number of specialized immune cells called CD4 cytotoxic T lymphocytes (CD4 CTLs). These cells are known to target and kill tumor cells in certain cancers. Researchers from the University of Osaka in Japan have published a study suggesting that this increased presence of CD4 CTLs may be associated with healthy aging in those who reach extreme old age.

Initially, the study observed that the proportion of CD4 CTLs increased as age increased, from 4% in individuals aged 70-99, to 9.6% in those aged 100-109, and 17.6% in individuals aged 110 and older. The researchers also discovered that these cells undergo clonal expansion, meaning they multiply rapidly in response to ongoing immune challenges.

This clonal expansion was particularly evident in one centenarian, where a single clone accounted for 53.8% of all CD4 CTLs. Additionally, the receptor sequences of these cells were found to match sequences from individuals diagnosed with cancer, particularly lung, breast, and liver cancers. However, none of the supercentenarians studied had been diagnosed with these cancers, leading researchers to believe that these CD4 CTLs may be mounting early responses to potential cancer-related targets.

While the study does not directly prove that high levels of CD4 CTLs contribute to longevity or cancer prevention, it suggests that these immune cells may play a role in maintaining the immune system's ability to adapt to age-related challenges and abnormal cells, such as senescent and cancerous cells, which become more common as we age. Further research is needed to fully understand the role of CD4 CTLs within human tissues.