Researchers say special cells clone themselves when immune system comes under attack<\/p>\n
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Rare cells found in centenarians may be helping preserve their longevity by killing cancers before they grow, a groundbreaking new study reveals.<\/p>\n
The specialised immune cells were known to kill some tumour cells. The new study, conducted by researchers at the University of Osaka in Japan, shows that they also play a role in healthy ageing among centenarians.<\/p>\n
The cells are called CD4 CTL and are a signature of supercentenarians who live past 110, researchers say.<\/p>\n
\u201cCD4 CTLs are an atypical and relatively rare T cell population,\u201d Kosuke Hashimoto, author of the new study published in the journal Cell Reports, said. \u201cSo, their marked increase in supercentenarians may provide important clues as to how the immune system is maintained in extreme old age.\u201d<\/p>\n
The cells clone themselves when the immune system is under attack \u2013 a process known as clonal expansion \u2013 indicating that they enable older adults to respond to persistent threats.<\/p>\n
In the study, researchers analysed blood samples of 28 adults divided into three age groups \u2013 70\u201399, 100\u2013109, and 110 and older \u2013 and found that the proportion of CD4 CTLs among a person\u2019s immune cells seemed to grow with age.<\/p>\n
\u201cThe selective expansion of certain T cells suggests that, even in extreme old age, the immune system may continue to adapt to age-related challenges,\u201d Dr Hashimoto said.<\/p>\n
CD4 CTL expansion seems to begin around the age of 100, researchers say, but it may not always be unique to centenarians and supercentenarians. In fact, it was a participant under the age of 100 who had the highest proportion of these cells.<\/p>\n
In one centenarian\u2019s blood sample, researchers found a single clone of CD4 CTLs accounted for over 50 per cent of their CD4 CTLs.<\/p>\n
Scientists then compared the structure of molecules on the surface of each participant\u2019s top CD4 CTL clone with molecules in a public database. Almost three dozen of the matches belonged to people with lung, breast, and liver cancers, the study found.<\/p>\n
Since none of the centenarians or supercentenarians had been diagnosed with any of these cancers, their CD4 CTL expansion likely reflected early immune responses against the development of cancer.<\/p>\n
\u201cSome CD4 CTLs may recognise cancer-related targets, although their exact targets remain unknown,\u201d Dr Hashimoto said.<\/p>\n
The study, however, does not prove that an abundance of CD4 CTLs in the body prevents cancer or causes a person to live longer.<\/p>\n