Staphylococcus aureus bacteria (artificially coloured) were injected into mice to cause the severe condition called sepsis.Credit: Science Source/SPL
Genes that protect the body against infection during youth can do harm in old age, according to a study1 in mice. The results hint that ageing lowers immunity in unexpected ways, not just by weakening the immune response.
The study’s authors report that the presence of a specific gene in the heart helped mice to survive virulent infections — but only if the mice were young. For old mice, the gene increased the risk of death.
“In one case it’s protective. In another case, it actually drives death,” says Andrew Wang, an immunologist at Yale University in New Haven, Connecticut, who was not involved in the research. The study shows that “the mechanisms that are protective to organs really can differ dramatically”.
These findings about how age affects the body’s ability to endure invasion from pathogens, published in Nature on 14 January, might be a step towards developing therapies for diseases distinguished by broad immune dysfunction that damages the body, researchers say.
Withstanding attack — and defence
Surviving an infection requires the immune system to fight off harmful invaders. But it also requires the body to avoid damage from pathogens and overzealous immune cells.
Young individuals often withstand both infection and the immune defences that are unleashed by their bodies to kill off infectious organisms. “But as you get older, your ability to do that reduces,” says Manu Shankar-Hari, an immunologist at the University of Edinburgh, UK.
Ageing is linked to inflammation — but only in the industrialized world
To understand why this endurance declines over an animal’s lifetime, Janelle Ayres — a co-author of the mouse study and an immunologist at the Salk Institute for Biological Studies in San Diego, California — and her colleagues studied a life-threatening condition called sepsis, which occurs when the immune system overreacts to an infection. The resulting immune storm causes organ damage and sometimes death. There are no targeted treatments beyond general antibiotics.
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