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UV rays: the sun dampens the immune system

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In summer, people like to be outdoors. Especially in our latitudes, where it is cold half of the year. But especially in midsummer it is important to only enjoy the sun protected and in moderation. Ultraviolet radiation is contained in the short-wave portion of solar radiation and, among other things, fulfills important functions for the metabolism.

However, there is also a risk of acute or chronic damage to health from UV radiation. Researchers at the Medical University of Graz have now examined the influence of UV radiation on the interaction between the skin's microbiome and the immune system.

Rays dampen the immune system

UV rays play an important role in metabolism, among other things, as they help the body to produce vitamin D. This vitamin then ensures, among other things, for building bones, supplies the muscles with calcium or supports the immune system. But here, too, as is so often the case - the amount counts, since overdosing is harmful to health and acute damage, such as sunburn, as well as chronic damage such as skin cancer can occur.

"UV radiation suppresses the skin's immune system, so it has an immunosuppressive effect. This creates a certain immune deficiency, which plays an important role in the development of skin cancer," explains Peter Wolf from the University Clinic for Dermatology and Venereology at the Medical University of Graz. The extent of the immune system suppression caused by UV radiation can be represented with a contact allergy model.

The researchers found that the skin's microbiome - the entirety of the microorganisms that colonize the skin - protects itself from the immunosuppressive effects of UVB radiation. "In the laboratory model we were able to clearly establish that the immune response to UVB radiation of a model with an intact microbiome clearly differs from that of a model without a microbiome," summarizes Wolf.

Skin microbiome

Under the influence of UV radiation, the microbiome on the skin creates a condition that promotes inflammatory processes, while the skin without a microbiome creates an increasingly immunosuppressive environment, i.e. the immune system no longer works to its full extent. "This condition is mainly caused by the increased expression of interleukin-10, a messenger substance of the immune system," describes Peter Wolf.

For example, if the skin is disinfected with an antiseptic, this leads to more immunosuppression after exposure to UV radiation. The skin can no longer protect itself adequately due to the no longer intact microbiome.

The research results have far-reaching significance, especially since the influence of skin care products, disinfectants, etc. on the microbiome could steer the immune response to UV radiation in one direction or the other. (red, July 2nd, 2019)