People Who Live More Than 100 Years May Not Have ‘Tired’ Immune Systems, They May Have Hyper-Vigilant Ones

 

We tend to think of ageing as a gradual process of things slowing down: the muscles lose strength, recovery takes longer, the vision gets blurry. But what if that story is incomplete? A small study from researchers at Osaka University suggests that people who live beyond 110 may have an immune system that does something rather different. Instead of declining with age, parts of it may reorganise and become unusually active.

The finding centres on a rare type of immune cell called CD4 cytotoxic T lymphocytes, or CD4 CTLs. In most people, CD4 T cells are thought of primarily as “helper” cells, coordinating the immune response, while CD8 T cells are the better-known cellular assassins. In super-centenarians, however, some CD4 cells appear to acquire powerful killing abilities, and they don't appear to be exhausted.

 

The researchers analysed immune cells from people in different age groups, including individuals in their 70s to 90s, centenarians and super-centenarians. CD4 CTLs remained relatively uncommon through much of adulthood, accounting for a median 4% of total T cells among people in their 70s to 90s. Among centenarians, that figure rose to 9.6%. Among people aged 110 and above, it reached 17.6%.

 

It suggests that something happens to the immune system around extreme old age. Rather than continuing along a simple downward slope, it appears to remodel itself. Lead author Kosuke Hashimoto described these cells as enriched in super-centenarians. “Rather than showing signs of exhaustion, they remain highly active and may help the body cope with persistent threats that increase with age,” he said.

CD4 T cells traditionally help coordinate immune responses. CD8 T cells are more directly associated with killing infected or abnormal cells. The CD4 CTLs found in unusually high numbers among super-centenarians combine some of these functions. They can recognise threats and destroy dangerous cells.

Age brings more exposure to infections, cellular damage and abnormal cells.