People who live to be 110 years old and beyond — known as supercentenarians — have a secret weapon in their immune system, and it may be one of the reasons why they’re able to live such long, healthy lives.
In a new study published in the Proceedings of the National Academy of Sciences, Japanese researchers collected blood samples from seven supercentenarians and five control participants (ranging from their 50s to their 80s), isolated and analyzed their immune cells and then compared the two groups.
The researchers found that while supercentenarians have fewer B cells — white blood cells that secrete antibodies to fight pathogens — than the control group, they have significantly higher numbers of a rare type of T cell in their blood.
To give some background, there are two types of T cells: helper cells and killer cells (also known as “cytotoxic” cells, which means they can kill other cells, such as when fighting off virus-infected cells or tumor cells).
“Killer T cells, or cytotoxic T cells, usually have a marker on them called CD8 that allows them to peek into cells and see if there’s an infected cell,” Jonathan Schneck, MD, PhD, a professor of pathology at Johns Hopkins Medicine, tells Yahoo Lifestyle. “Immune cells function in a very orchestrated fashion. CD8 cells don’t function by themselves; they need help from other cells, and one of them that provides a lot of help is the CD4 helper T cell.”
In the case of the supercentenarians, however, the researchers found that most of their immune cells came from a subset of T cells called CD4 CTLs — a helper cell that can actually attack and kill other cells. “It is a relatively unique set of T cells,” Schneck says.
VJ Periyakoil, MD, director of the Stanford Successful Aging Program, explains to Yahoo Lifestyle that these are “very specialized immune cells that help our body in fighting virus infections and cancer. These cells secrete two compounds called granzyme B and perforin, which kill intruder cells upon direct contact.”
A 2017 study noted that these special T cells “play important roles in antiviral and antitumor immunity, as well as in inflammation.”
The study authors were surprised by the results. “This characteristic is very unique to supercentenarians,” they wrote, “because generally CD4 T cells have helper, but not cytotoxic, functions under physiological conditions.”
They added that these unique cells “may represent an essential adaptation to achieve exceptional longevity by sustaining immune responses to infections and diseases.”
“Maybe that’s helping in terms of getting past many of the challenges we have in terms of old age, as people become elderly and frail,” Schneck tells Yahoo Lifestyle, referring to the special cells. “Those cells may be helping them clear what could be nascent cancer cells, or they could help protect them from infection — all of the things that the very elderly are particularly susceptible to.”
Periyakoil says a robust immune system is necessary for a lengthy, healthy life, but parts of the immune system can weaken with age. “As we get older for most of us, the immune system becomes less efficient, putting us at risk for cancers and infections,” she says. “If your immune system continues to be very efficient in killing bugs and cancer cells, you are likely to lead a long and healthy life.”
In a statement to Live Science, study co-authors Kosuke Hashimoto, Nobuyoshi Hirose and Piero Carninci wrote: "The key will be to understand what is [the cells'] natural target, which may help to reveal what is needed for a healthy, long life.”
Supercentenarians are a rare club. According to the Gerontology Research Group, there are 31 validated supercentenarians living around the world (30 are women, one is male).
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