Researchers have discovered that the central nervous system and immune system are directly connected via lymphatic vessels in the lining of the dural sinuses, according to new research published in Nature.
Until now, scientists have had little understanding about how immune cells entered and exited the central nervous system. This new discovery challenges long-held assumptions about neuroimmunology. The discovery has critical implications for the way scientists study neuro-immune interaction.
“We always perceived it before as something esoteric that can’t be studied,” said Jonathan Kipnis, PhD, of the University of Virginia. “But now we can ask mechanistic questions.”
The researchers believe their discovery will have major effects on the study and treatment of all neurological diseases that have immune components, from Alzheimer’s disease to multiple sclerosis.
Although the lymphatic system has been mapped thoroughly throughout the body, these vessels had remained undetected. The researchers say it is due to their location; the vessels follow a major blood vessel down to the sinuses and are easy to overlook.
Antoine Louveau, a postdoctoral fellow at the University of Virginia, found the vessels while studying mice. He developed a method of mounting mice’s meninges on a single slide. By fixing the meninges with a skullcap, the tissue is held in its physiological condition and then dissected.
The researchers detected patterns that resembled vessels when they looked at the immune cells of mice. Testing for lymphatic vessels confirmed their presence. The structures have all of the hallmarks of lymphatic endothelial cells. They can carry fluid and immune cells from the cerebrospinal fluid and are connected to deep cervical lymph nodes.
In terms of neurological disorders, the discovery of these vessels creates a myriad of new questions that now need to be explored or revisited. The researchers have already begun to hypothesize the roles the vessels could play. “In Alzheimer’s, there are accumulations of big protein chunks in the brain,” Kipnis said. “We think they may be accumulating in the brain because they’re not being efficiently removed by these vessels.”
Further research will seek to precisely determine how these vessels play into various neuro-immunological disorders.