Researchers Find Missing Link Between the Brain and Immune System
Maps of the lymphatic system: old (left) and updated to reflect UVA’s discovery. Image credit: University of Virginia Health System.
As to how the brain’s lymphatic vessels managed to escape notice all this time, Kipnis described them as “very well hidden” and noted that they follow a major blood vessel down into the sinuses, an area difficult to image. “It’s so close to the blood vessel, you just miss it,” he said. “If you don’t know what you’re after, you just miss it.”
“Live imaging of these vessels was crucial to demonstrate their function, and it would not be possible without collaboration with Tajie Harris,” Kipnis noted. Harris, a PhD, is an assistant professor of neuroscience and a member of the BIG center. Kipnis also saluted the “phenomenal” surgical skills of Igor Smirnov, a research associate in the Kipnis lab whose work was critical to the imaging success of the study.
Alzheimer’s, Autism, MS and Beyond
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. For example, take Alzheimer’s disease. “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.” He noted that the vessels look different with age, so the role they play in aging is another avenue to explore. And there’s an enormous array of other neurological diseases, from autism to multiple sclerosis, that must be reconsidered in light of the presence of something science insisted did not exist.
About this neuroscience research
The findings have been published online by the prestigious journal Nature and will appear in a forthcoming print edition. The article was authored by Louveau, Smirnov, Timothy J. Keyes, Jacob D. Eccles, Sherin J. Rouhani, J. David Peske, Noel C. Derecki, David Castle, James W. Mandell, Lee, Harris and Kipnis.
Funding: The study was funded by National Institutes of Health grants R01AG034113 and R01NS061973. Louveau was a fellow of Fondation pour la Recherche Medicale.
Source: Debra Kain – University of Virginia Health System Image Source: The image is credited to the University of Virginia Health System Original Research: Abstract for “Structural and functional features of central nervous system lymphatic vessels” by Antoine Louveau, Igor Smirnov, Timothy J. Keyes, Jacob D. Eccles, Sherin J. Rouhani, J. David Peske, Noel C. Derecki, David Castle, James W. Mandell, Kevin S. Lee, Tajie H. Harris and Jonathan Kipnis in Nature. Published online June 1 2015doi:10.1038/nature14432
Structural and functional features of central nervous system lymphatic vessels
One of the characteristics of the central nervous system is the lack of a classical lymphatic drainage system. Although it is now accepted that the central nervous system undergoes constant immune surveillance that takes place within the meningeal compartment1, 2, 3, the mechanisms governing the entrance and exit of immune cells from the central nervous system remain poorly understood4, 5, 6. In searching for T-cell gateways into and out of the meninges, we discovered functional lymphatic vessels lining the dural sinuses. These structures express all of the molecular hallmarks of lymphatic endothelial cells, are able to carry both fluid and immune cells from the cerebrospinal fluid, and are connected to the deep cervical lymph nodes. The unique location of these vessels may have impeded their discovery to date, thereby contributing to the long-held concept of the absence of lymphatic vasculature in the central nervous system. The discovery of the central nervous system lymphatic system may call for a reassessment of basic assumptions in neuroimmunology and sheds new light on the aetiology of neuroinflammatory and neurodegenerative diseases associated with immune system dysfunction.
“Structural and functional features of central nervous system lymphatic vessels” by Antoine Louveau, Igor Smirnov, Timothy J. Keyes, Jacob D. Eccles, Sherin J. Rouhani, J. David Peske, Noel C. Derecki, David Castle, James W. Mandell, Kevin S. Lee, Tajie H. Harris and Jonathan Kipnis in Nature. Published online June 1 2015 doi:10.1038/nature14432