Researchers have uncovered new details on how some diseases affect the brain. 

A new Australian study shows how cells can communicate across the brain’s protective blood-brain barrier.

The finding could change the current understanding of what happens in patients with deadly diseases such as malaria.

Malaria leads to around 500,000 deaths worldwide each year. The most severe part of the infection is ‘cerebral malaria’, in which infected T-cells accumulate in the brain, often leaving patients in a coma. Mortality is high, and surviving patients have an increased risk of neurological and cognitive deficits, behavioral difficulties and epilepsy.

Using a high-tech laser microscopy imaging model, researchers have taken a rare peek inside blood vessels to watch immune cell behaviour in real-time.

“What we saw was a group of immune cells called ‘T-cells’, driving inflammation in the brain and we found they don’t act alone, they need a licence to kill,” says Dr Saparna Pai from James Cook University’s Australian Institute of Tropical Health and Medicine.

“We now know they are guided by another specialised cell known as perivascular macrophages (PVM), which we saw guiding the T-cells across the blood vessel, through the blood brain barrier, into the brain.”

In a patient with cerebral malaria, the red blood cells become ‘sticky’, blood flow becomes sluggish, and the endothelium membrane lining the blood vessels also becomes inflamed.

Recently, researchers in the US found T-Cells also get stuck to the endothelium membrane and were able to find their way into the brain.

Existing medical understanding is that this membrane lining the blood vessel is what attracts and assists the T-Cells to cross the blood brain barrier.

But this new research shows that PVM play an important role.

“Several studies have demonstrated the indispensable role of these T cells in the development of cerebral malaria, but their precise activities within the brain that contribute to neurological disease were only recently documented by our group,” Dr Pai said.

“PVM cells communicating with T cells across the blood-brain barrier is a highly innovative concept that has not been previously identified”.

If the team’s findings can be validated, they may provide a new therapeutic target for the treatment of several diseases in which PVM play a crucial role in disease progression.

These diseases include multiple sclerosis, where the T-cells cross the blood brain barrier and find their way into the second layer of brain tissue, and may also have implications for the prevention and treatment of diseases such as Alzheimer’s and viral encephalitis.

The full study is accessible here.