Author response: Internalization and presentation of myelin antigens by the brain endothelium guides antigen-specific T cell migration

Le résumé fourni par la source

The blood vessels in the brain help to control the entry of nutrients, cells and waste products into and out of the brain. In doing so, they create a protective barrier between the blood and the brain known as the blood-brain barrier. However, this barrier loses its protective function in individuals with multiple sclerosis or other disorders that affect the brain. Multiple sclerosis patients develop inflammation and their immune cells become able to enter the brain. These immune cells may then attack layers of insulation called myelin that surround nerve cells. Myelin helps nerve cells to work properly so the loss of this insulation can lead to tissue damage and cognitive problems. When immune cells called T cells enter the brain they can become primed to recognize myelin and attack it in the same way that they would attack viruses or bacteria. However, it is not clear precisely how these T cells develop the ability to cross the blood-brain barrier and attack myelin. Now, Lopes Pinheiro et al. show that “endothelial” cells in the blood-brain barrier are able to present fragments of myelin to T cells, which enables the T cells to identify myelin and move into the brain. First, the blood-brain barrier cells absorb and break down proteins in the myelin, and then they present fragments of these proteins on their surfaces with the help of protein clusters called major histocompatibility complexes (MHCs). Other protein fragments that can also activate T cells in other parts of the body did not affect the blood-brain barrier when they were presented by MHCs, which suggests that the effect could be specific to myelin proteins. The experiments also show that it is possible to stop T cells from crossing the blood-brain barrier by preventing them from interacting with myelin fragments presented by MHCs. This suggests that therapies that interfere with the ability of blood-brain barrier cells to break down myelin proteins and present them to T cells might help to protect the brains of patients with multiple sclerosis.

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