More Than Effects in Skin: Ultraviolet Radiation-Induced Changes in Immune Cells in Human Blood

Abstract

Cells of the skin and circulation are in constant two-way communication. Following exposure of humans to sunlight or to phototherapy, there are alterations in the number, phenotype and function of circulating blood cells. In this review, only data obtained from human studies are considered, with changes induced by UV radiation (UVR) exposure described for phagocytic leukocytes and peripheral blood mononuclear cells plus their component T and B cells, natural killer cells and dendritic cells. These immune modulations illustrate the potential of UVR to have therapeutic effects beyond the skin, and that sunlight exposure is an important environmental influence on human health.

Pilot phase results of a prospective, randomized controlled trial of narrowband ultraviolet B phototherapy in hospitalized COVID‐19 patients

“…Decades of clinical experience with NB‐UVB in GvHD and other autoimmune, dermatologic diseases have shown that NB‐UVB stabilizes the immune system. Mechanistically, the skin is a complex organ containing a reservoir of photo‐reactive cells that communicate extensively with our systemic immune systems 2,3,18,19 . Exposure to UV radiation triggers numerous molecular responses in the skin, activating biological cascades that push immune responses towards homeostasis typified by reduced Th1 and Th17 and increased Th2 and circulating regulatory T cells and ameliorates symptoms in acute GVHD by expansion of CD4+ CD25+ Foxp3+ 19,20 .…”

“…Mechanistically, the skin is a complex organ containing a reservoir of photo‐reactive cells that communicate extensively with our systemic immune systems. 2 , 3 , 18 , 19 Exposure to UV radiation triggers numerous molecular responses in the skin, activating biological cascades that push immune responses towards homeostasis typified by reduced Th1 and Th17 and increased Th2 and circulating regulatory T cells and ameliorates symptoms in acute GVHD by expansion of CD4+ CD25+ Foxp3+. 19 , 20 Downstream effects include decreased pathologic inflammation and improved intracellular killing of pathogens.…”

“… 2 , 3 , 18 , 19 Exposure to UV radiation triggers numerous molecular responses in the skin, activating biological cascades that push immune responses towards homeostasis typified by reduced Th1 and Th17 and increased Th2 and circulating regulatory T cells and ameliorates symptoms in acute GVHD by expansion of CD4+ CD25+ Foxp3+. 19 , 20 Downstream effects include decreased pathologic inflammation and improved intracellular killing of pathogens. Improvements in hemostatic regulation may also be driving patient benefit as UVB increases the cytokine IL‐10 that can inhibit both LPS‐induced activation of coagulation and fibrinolysis.…”

“…and increased Th2 and circulating regulatory T cells and ameliorates symptoms in acute GVHD by expansion of CD4+ CD25+ Foxp3+. 19,20 Downstream effects include decreased pathologic inflammation and improved intracellular killing of pathogens.…”

The Exposome and Immune Health in Times of the COVID-19 Pandemic

“…Ultraviolet radiation exerts immunomodulatory effects independent of vitamin D [ 195 ]. For instance, ultraviolet radiation-induced immunosuppression is key to the development of carcinogenesis in the skin [ 196 ].…”