"It has something to do with light"
Around 2.5 million people worldwide suffer from multiple sclerosis. Scientists are largely in the dark about how and why this chronic inflammatory disease develops, but it evidently has something to do with light – because one thing that is striking is that northern Europeans, north Americans and Canadians develop this disease much more frequently than people in countries near the equator.
If babies or small children move to a region with statistical higher sun exposure, the risk of getting multiple sclerosis adapts to the new environment. So do environmental factors, particularly solar radiation, have an influence on the immune system? Researchers at Münster University set out to investigate. Their results showed that moderate sunlight supports the build-up of a healthy immune system and helps it in protecting the central nervous system.
A similar effect in the case of other diseases is already known, reports Prof. Karin Loser from the University Department for Dermatology. "From our treatment of psoriasis," she says, "we know that ultraviolet light has a positive effect on the immune system." In collaboration with the dermatologists, and working on both animals and a number of people affected, neurologists at the University Clinic analysed whether this also applied to other diseases.
Over a period of six weeks, nine patients with multiple sclerosis went into a specially designed medical solar chamber. Radiation was carried out every day except for the weekends. "The results are astonishing," says Loser. "After the first session there were already more regulatory T-cells and dendritic cells than before in the patients' blood and skin." Both types of cells protect the immune system from attacking itself in the case of an overreaction – a dangerous process that is the central feature of multiple sclerosis. On the basis of skin biopsies the team of scientists was able to demonstrate that UVB radiation triggers a complex process in the immune system of patients with multiple sclerosis: in the skin exposed to radiation, tolerogenic dendritic cells are formed which then "cultivate" regulatory T-cells in attached lymph nodes.
Parallel to this, it was possible to decode in mice the exact molecular paths which play a role in UVB radiation: the induced regulatory cells migrate from the skin to the place of inflammation, i.e. into the blood, the bones or – as in the case of multiple sclerosis – into the central nervous system. Here, they trigger a protective reaction of the immune system and thus curb any harmful autoimmunity. If the treatment was interrupted just for a few days, the blood values and immune status deteriorated again – both in mice and in humans.
The results show clearly how the environmental factor of ultraviolet light influences the emergence and developement of multiple sclerosis. "There is evidently a relevant axis between the skin and the nervous system," concludes Prof. Heinz Wiendl, Director of the Department of Neurology in Münster. "UVB radiation has an influence on the immunotolerance in the nervous system. The influence is short-term, reversible and goes far beyond the effects of vitamin D alone." The authors of the study do not as yet see in their findings a basis for any concrete new therapy. These findings could, however, help to increase and improve the possibilities of treating multiple sclerosis.
The project was supported by the German Research Foundation, as well as by the Disease-Related Multiple Sclerosis Competence Network. The research was undertaken as part of Collaborative Research Centre 128, "Multiple Sclerosis", and of the "Cells in Motion" Excellence Cluster.
Publication:
Breuer J, Schwab N, Schneider-Hohendorf T, Marziniak M, Mohan H, Bhatia U, Groß CC, Clausen BE, Weishaupt C, Luger TA, Meuth SG, Loser K, Wiendl H. UVB light attenuates the systemic immune response in CNS autoimmunity. Annals of Neurol. 2014 [Epub 28 Apr 2014]