Researchers in Japan have discovered something unique about the immune systems of supercentenarians who live to 110 years of age.
Thousands of immune cells from seven supercentenarians and five controls had their RNA sequenced to deduce which genes were expressed in each cell (PNAS, 2019, 116, (48), 24242). It turned out that supercentenarians boasted far more CD4 T cells with the ability to kill other cells.
Usually CD4 cells are considered helper T cells, facilitating the immune response rather than directly killing bacteria and viruses. Ordinarily, CD8 cells are the killer cells.
However, it is now known that cytotoxic CD4 T cells, though rare, play an important role in immune surveillance and boast strong anti-tumour and anti-viral properties. On average 25% of the CD4 T cells of supercentenarians were cytotoxic, reaching 80% of T cells in some, against 10 to 25% in controls aged 50 to 80 years of age.
Piero Carninci at the RIKEN Center for Integrative Medical Sciences in Japan says one possible reason supercentenarians boast high levels of these cells is they may have helped protect them against cancer or viral infections. If so, ‘one may think to induce these cells as a general strategy to improve health and longevity.’
Immunologist Guillaume Spielmann at Louisiana State University, US, says one can hypothesise that selective expansion of cytotoxic CD4 T cells could ‘improve immune health in older adults’. His research shows that increased physical activity is associated with reduced signs of immune ageing in older adults. He adds that ‘it would be interesting to study the impact of frequent and increased aerobic fitness on the proportions of cytotoxic CD4 T-cells’.
Another explanation, says immunologist Sian Henson at Queen Mary University of London, US, may be that supercentenarians are truly unique and benefit by naturally having more of these killer cells. Alternatively, ‘perhaps this population of cells accumulates as we grow older, and if we all lived to 110, we would all have them’.
Living to 110 is extremely rare. In Japan, there were more than 61,000 people over the age of 100 in 2015, but just 146 over the age of 110.
Spielmann notes that ‘a larger study needs to be conducted before generalising these findings to the larger population’. Henson also points out that all were Japanese, with a non-Western diet, and says it will be interesting to replicate the study in other parts of the world.