Photo: microscope slide showing stained immune cells

Under the microscope: meet your inner warriors

Immune cells are the heroes in the blood and brain – until they go rogue.

In MS, the immune system goes wrong and starts to attack the protective myelin coating around our nerves. Learning more about the immune system helps us develop treatments to stop these attacks from happening.

The immune system is made up of a diverse cast of characters, all with a unique role to play in protecting our bodies from harm. Here we introduce four of the most important immune cell types in MS.

T cells

How they work: T cells play a key role in defending the body from all kinds of danger. There are a few different types of T cells, some of which help coordinate the immune response, while others kill infected cells. 

Importance in MS: T cells have been found in lesions within the central nervous system in MS. And some T cells that can increase inflammation are found at higher levels during a relapse. Many of the current disease modifying therapies (DMTs), including natalizumab (Tysabri), alemtuzumab (Lemtrada), and fingolimod (Gilenya), work by targeting T cells.

Latest insights: Dr Anne Astier’s team in Edinburgh is investigating how T cells move into the brain in MS. They’re focusing on a protein called CD46, which is found on certain T cells. CD46 doesn’t work properly in MS, and this could affect how T cells get into the brain from the blood. 

An international collaboration led by Dr Denise Fitzgerald from Queen’s University Belfast has also shown that one type of T cell can actually help repair myelin instead of attacking it, at least in mice. This unexpected finding demonstrates how complicated the immune system can be, and how more research is needed. 

B cells

How they work: B cells produce antibodies in response to infection. Antibodies can stick to microbes and stop them getting into our cells or multiplying, so they can help our bodies dispose of threats. 

Importance in MS: B cells are found in the central nervous system in MS. The presence of antibodies in the spinal fluid (often called oligoclonal bands) is one of the tests used to diagnose MS.

Latest insights: Research suggests that B cells and antibodies are important in MS, but we still don’t fully understand their role. Professor Chris Linington, from the University of Glasgow, wants to know more. His team have recently uncovered a new way that antibodies could be causing damage in MS.

Natural killer cells

How they work: Natural killer (NK) cells help to defend us against viruses by killing infected cells. 

Importance in MS: Scientists have found differences in both the number and type of NK cell in people with and without MS. And certain genes linked to MS can control how NK cells work.

Latest insights: Professor Daniel Altmann, and his team at Imperial College London, is learning more about how NK cells behave in people with relapsing MS. They want to know if this is different between people who have highly active MS or not, or those who are on treatment. If we know how NK cells are involved in MS, we can design treatments to stop them going wrong.

Microglia

Photo: Microglia cells stained red and green

How they work: Microglia are specialised immune cells that live in the central nervous system full time. These fickle cells are the frontline defenders of the brain.

Importance in MS: Scientists have found that microglia play two opposing roles in MS. When they’re behaving properly, microglia can help to prevent nerve cell damage and repair myelin. But as MS gets worse, these cells not only fail to protect nerves from harm, they can also start to cause damage themselves.

Latest insights: In Edinburgh, Dr Veronique Miron is interested in proteins produced by microglia that could boost myelin repair. And Professor Sandra Amor at the University of London is particularly interested in one protein made by microglia, called TSPO. Targeting TSPO has been shown to keep nerves alive in mice.

Both of these projects could help us on our way to developing drugs that help repair myelin and protect nerves from damage.

> Find out about current disease modifying therapies (DMTs) that help stop immune attacks

This blog first appeared in Research Matters magazine. To receive Research Matters by post please contact supportercare@mssociety.org.uk about subscription. You can also download the full issue for free.

Images: Immune cells by Owain Howell (top) and microglia by Deborah Kronenburg-Versteeg (bottom).

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