VITAMIN D may help repair damaged brain tissue in patients with multiple sclerosis by interacting with the white blood cells responsible for dampening down the body's immune response, according to research due to be presented in Edinburgh today [thu].

It has long been observed that rates of MS increase the further populations are from the equator, as the decline in exposure to sunlight also hampers the body's ability to generate vitamin D. Scotland and Canada have the highest prevalence of MS worldwide, but so far scientists have been unable to prove a cause-and-effect link between vitamin D deficiency and MS.

However, research due to be presented on the opening day of the MS Frontiers conference suggests that the vitamin appears to play a role in guiding white blood cells, known as T cells, towards the brain. The study uses zebrafish which have had one side of their brain damaged to mimic MS. The fish - which are transparent - are then immersed in water enriched with vitamin D. The T cells in their bodies have also been engineered to glow fluorescent green so that the researchers can observe their movement under a microscope and determine whether they migrate towards the damaged side of the brain.

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So far the research, which is funded by the MS Society, has found that vitamin D does appear to influence the movement of T cells in a test tube setting. Early indications suggest that the same pattern is occurring in the zebrafish, but the researchers are still awaiting results which would back up recommending vitamin D as an alternative to some MS drug treatments.

Dr Anne Astier, a specialist in inflammation research at Edinburgh University, said: "We have been through the stage where we have the model working and, if we do injure the brain, we can see those green T cells moving towards the brain.

"If you look at some of the drugs already prescribed in MS, the principle is to block migration of aggressive T cells to the brain. They do that by targetting one of those molecules that is involved in the migration of those cells. We think that vitamin D may do the same and if so it might be easier just to give patients vitamin D rather than those drugs - but we don't know that yet."

Crucially, the scientists must find out which type of T cell vitamin D is interacting with in the zebrafish. There are three types: "helper" T cells which boost the body's immune response, "regulatory" T cells which dampen the immune response, and "killer" T cells which attack perceived toxins.

It is the regulatory T cells which vitamin D must harness to be useful in MS. This is because MS is widely considered to be an auto-immune disease caused when the sufferer's own immune system turns on them, attacking the central nervous system and leading to disability.

To date, it is unknown what triggers this faulty immune response, but a combination of genetic and environmental factors are believed to be at play.

Dr Astier added: "We do see the T cells moving to the brain but we don't have the results yet to know whether the damaged part of the brain is being repaired. It depends what type of T cells are being guided there. If it's the aggressive T cells they will actually create more inflammation; if we manage to drive in the regulatory T cells, then it it might be beneficial."