Photo/Illutration Kane Tanaka, a 116-year-old resident of Fukuoka, celebrates Respect-for-the Aged Day in September. She is recognized as the oldest living person by Guinness World Records. (Asahi Shimbun file photo)

The so-called supercentenarians who reach or live beyond their 110th birthdays have an abnormally large amount of special immune cells in their blood that could contribute to their longevity, Japanese researchers said.

The study was conducted by a team of scientists from the Riken Center for Integrative Medical Science and Keio University School of Medicine’s Center for Supercentenarian Medical Research.

The results were carried in the Nov. 13 edition of U.S. science journal Proceedings of the National Academy of Sciences (PNAS).

In general, as people age, their risk of developing cancer or infectious diseases increases because of a decline in their immunological capacity.

But supercentenarians are less prone to such diseases, and many of them live without assistance even when they turn 100. They are touted as the “elite of health and longevity.”

Through blood samples, the team compared immune cells of seven supercentenarians with those of five subjects in their 50s through 80s.

The scientists discovered a significant difference in the composition of T cells, which play a key role in the immune system, between the two groups.

In particular, the share of the CD4+ T Cell stood at about 25 percent of T cells in the blood of the supercentenarians. Among average people, the ratio is usually in the single digits.

However, the researchers have yet to determine why supercentenarians have a significantly larger amount of that particular T cell. They also have not discerned how that T cell works in terms of extending lives.

“The composition of T cells changes as people age,” said Kosuke Hashimoto, a researcher with the Riken Center for Integrative Medical Science. “If we can find the link between the immune system and aging and longevity, we may be able to contribute to prolonging healthy life expectancies.”

Japan, with a population of 127 million, has around 150 supercentenarians.