Scientists who study centenarians say key to living beyond 100 is lots of exposure to infections

It might sound counterintuitive, but scientists say one key to living beyond 100 is plenty of experience fighting off infections.

Researchers who studied the DNA of seven centenarians found they all shared one thing in common — they’d fought lots of bugs and viruses.

Their subjects had a high number of B cells, immune cells and antibodies needed to fight off old foes.

Scientists are trying to work out whether catching and beating infections is the key, or whether centenarians are just genetically stronger in the immune department.

Lead author of the study, Paola Sebastiani, a biostatistician at Tufts University in Boston, said the immune profiles of centenarians show ‘a long history of exposure to infections and capacity to recover from them.’

‘We believe that centenarians have protective factors that allow them to survive the Spanish Flu, survive Covid,’ she told DailyMail.com

The study, which also included scientists from Boston University, looked at blood samples from seven centenarians between the ages of 100 and 119 years old.  

The team isolated a critical part of the participants’ immune systems: peripheral blood mononuclear cells (PBMCs), a kind of immune cell that originates in bone marrow.

The researchers then subjected these immune cells to a battery of tests, comparing them to blood samples from two younger subjects, both with no extreme longevity themselves, nor any centenarians in their own family history. 

The team noticed a dramatic shift in the centenarians’ mix of immune cells: significantly more B cells than CD4+ T cells, indicating that their immune system had earned decades of hard-won experience fighting off natural and environmental infections.   

All told, the study examined the proportion of 13 subtypes of B cells and T cells, noticing a major shift in the ratio away from the innate fighters to the more adapted, experienced cell types. 

‘Centenarians harbor unique, highly functional immune systems that have successfully adapted to a history of insults,’ the study concludes, ‘allowing for the achievement of exceptional longevity.’ 

But the scientists can’t yet say definitively whether or not their results show a hereditary predisposition towards an extremely long life or whether it’s all just evidence of their centenarians’ seasoned immune systems.

‘We know that there are many hereditary factors that are shared by centenarians,’ Sebastiani told the Mail. ‘We are not able—yet—to make the direct connection between these factors and what we see in their blood, in terms of their immune cell types.’ 

Sebastiani and her team did, however, identify 25 specific genes that were much more active in the centenarians, revealing a genetic pattern for extreme longevity. 

Among these, they found a much greater use of the gene STK17A, known to be involved in repairing damaged DNA, and HLA-DPA1, a gene that creates the antigens needed to tag certain infections inside the body.

They also found one gene, S100A4, that was entirely unique to centenarians. S100A4, part of the S100 family studied in age-related disease, is connected both to longevity and regulating metabolism.  

Ultimately, the team’s analysis, published last Friday in The Lancet, admits that ‘we cannot determine whether these EL [Extreme Longevity] specific patterns are the drivers to extreme human longevity or the effect of extreme old age.’

The trick, according to Sebastiani, will be to develop new studies in which future centenarians are measured and observed over time, a task that’s already underway. 

‘We have more than one study in which we have enrolled offspring of centenarians,’ Sebastiani said. ‘Most of them will become centenarians themselves—and we are collecting their blood over time.’ 

‘So, sometime hopefully soon we’ll have a better answer about inheritability of these characteristics.’