Study adds fuel to growing evidence that the immune system does more than fight disease.

Researchers have discovered that the immune system helps out the brain, in the absence of any disease, by making a chemical messenger that boosts memory.

The study was in mice, but senior author Bruno Silva-Santos, from the University of Lisbon, Portugal, says the finding could lead to dietary recommendations to improve memory in people.

The study is part of a rising tide of research upending the traditional view that the immune system exists only to fight infection and tumours.

The authors point out that disease is relatively rare, and so maintaining a complex system of immunity would impose a big cost if busting microbes and cancer were the only benefit.

Already, they say, immunity is known to have non-disease roles in temperature control and bone repair. But to accept that the immune system could be a major player in the everyday workings of the brain, another shibboleth in medicine must fall by the wayside.

“The brain was seen as an immune privileged organ, meaning that it would be completely shielded by the blood brain barrier and completely hermetic to the peripheral immune system,” explains senior author Julie Ribot, in a linked video.

Recently, says Ribot, it has been found that lymphatic vessels, which transport infection-fighting white blood cells, are present in the lining of the brain, called the meninges.

“This is really important,” says Ribot, “because it suggests that actually the brain and the immune system do constantly communicate, even when we are not sick.”

Read the full story in Cosmos magazine here