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Researchers have discovered the reason behind immune system aging and weakening with time, according to a new study. 

"We have found the cellular mechanism responsible for the inability of blood-forming cells to maintain blood production over time in an old organism, and have identified molecular defects that could be restored for rejuvenation therapies," said Emmanuelle Passegué, PhD, a professor of medicine and a member of the Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF, in the press release. 

Blood and immune cells have shorter lives and unlike most tissues, these must be constantly replenished. Cells that must keep producing them throughout a lifetime are called hematopoietic stem cells. 

Through cycles of cell division these stem cells preserve their own numbers and generate the daughter cells that give rise to replacement blood and immune cells. But the hematopoietic stem cells falter with age, because they lose the ability to replicate their DNA accurately and efficiently during cell division, the press release explained. 

"Everybody talks about healthier aging," Passegué added. "The decline of stem-cell function is a big part of age-related problems. Achieving longer lives relies in part on achieving a better understanding of why stem cells are not able to maintain optimal functioning."

Researchers hope that it might be possible to prevent declining stem-cell populations by developing a drug to prevent the loss of helicase components needed to faithfully unwind and replicate DNA and ultimately avoiding the immune-system failure. 

The study has been published in the journal Nature.