A team of researchers has discovered the ‘missing’ link between the brain and the immune system that may better treat neurological diseases such as Alzheimer’s and multiple sclerosis in the near future.

Researchers from University of Virginia’s School of Medicine found that brain, like every other tissue, is connected to the peripheral immune system through meningeal lymphatic vessels. The vessels may explain current medical mysteries such as why patients with Alzheimer’s disease have accumulations of large protein plaques in the brain.

The vessels also appear different as people age, suggesting that they may play a key role in the ageing process.

‘I really did not believe there are structures in the body that we are not aware of. I thought the body was mapped. I thought that these discoveries ended somewhere around the middle of the last century. But apparently they have not,’ said lead researcher Jonathon Kipnis, director of centre for brain immunology and glia at University of Virginia.

‘We believe that for every neurological disease that has an immune component to it, these vessels may play a major role. [It is] hard to imagine that these vessels would not be involved in a [neurological] disease with an immune component,’ he added.

The discovery was made possible by the work of Antoine Louveau, a postdoctoral fellow in Kipnis’ lab.

The vessels were detected after Dr Louveau developed a method to mount a mouse’s meninges.

After noticing vessel-like patterns in the distribution of immune cells on his slides, he tested for brain’s elusive lymphatic vessels and there they were. The impossible existed.

‘It was so close to the blood vessel, you just miss it. If you do not know what you are after, you just miss it,’ Dr Kipnis said.

The unexpected presence of the lymphatic vessels raises a tremendous number of questions that now need answers, both about the workings of the brain and the diseases that plague it.

‘We think they may be accumulating in the brain because they are not being efficiently removed by these vessels,’ Dr Kipnis added.

The study appeared in the journal Nature.