Lymphatic vessels: the connection between the Brain and the Immune system New pieces in the puzzle of Autism?

Discovery of hidden structures

One of the principal dogma concerning the central nervous system has just fallen:
brain and immune system are connected by lymphatic vessels.
Until a recent discovery made by researchers at the University of Virginia school of Medicine and published in the journal Nature (/documents/import/Louveau_2015.pdf), it was admitted that the lymphatic system was absent in the brain as it remained unidentified.

By developing a new technique to maintain the integrity of the lymphatic vessels, easily confoundable with the blood vessels and by visualizing meninges (the membrane covering the brain) as a whole in mice, Dr Louveau and his collaborators were able to localize vessels positive for specific markers of lymphatic endothelial cells surrounded by in a complex network of immune cells.

Figure 1: Old schematic representation of the lymphatic system (left), updated map including UVA discovery (right). Picture: Courtesy of the University of Virginia Health System.

New components of neuroinflammatory diseases

The presence of a functional and classical lymphatic system in the central nervous system suggests that this structure could carry fluid and immune cells from the cerebrospinal fluid thus directly impacting the brain microenvironment.

As stated by the authors:” Malfunction of the meningeal lymphatic vessels could be a root cause of a variety of neurological disorders in which altered immunity is a fundamental player”.

It is too early to confirm the involvement of the lymphatic drainage system in the etiology of autism. Nevertheless, this stunning study confirms the cross-talk existing between the immune system and the brain.
The lymphatic vessels could be a possible vector for the transit of immune cells thus playing a key role in brain inflammation.