Sunlight Effects on Immune System: Is There Something Else in addition to UV-Induced Immunosuppression?

Abstract

Sunlight, composed of different types of radiation, including ultraviolet wavelengths, is an essential source of light and warmth for life on earth but has strong negative effects on human health, such as promoting the malignant transformation of skin cells and suppressing the ability of the human immune system to efficiently detect and attack malignant cells. UV-induced immunosuppression has been extensively studied since it was first described by Dr. Kripke and Dr. Fisher in the late 1970s. However, skin exposure to sunlight has not only this and other unfavorable effects, for example, mutagenesis and carcinogenesis, but also a positive one: the induction of Vitamin D synthesis, which performs several roles within the immune system in addition to favoring bone homeostasis. The impact of low levels of UV exposure on the immune system has not been fully reported yet, but it bears interesting differences with the suppressive effect of high levels of UV radiation, as shown by some recent studies. The aim of this article is to put some ideas in perspective and pose some questions within the field of photoimmunology based on established and new information, which may lead to new experimental approaches and, eventually, to a better understanding of the effects of sunlight on the human immune system.

Activation of a protumorigenic IFNγ/STAT1/IRF‐1 signaling pathway in keratinocytes following exposure to solar ultraviolet light

“…9 In animal models, UV-induces systemic immunosuppression involves the development of antigen-specific regulatory T-cells (CD4+CD25+foxp3+cells), which can be transferred into nonexposed animals. 103,104 While further work is necessary, upregulation of PD-L1 after exposure to SUV may play an important role in local immune suppression during skin carcinogenesis.…”

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

“…[186][187][188][189][190][191][192][193][194][195] Ultraviolet (UV) radiation effects on local skin immunity are especially relevant to research on photocarcinogenesis or inflammatory skin conditions. [196][197][198] Effects vary with dose, duration of exposure and wavelength composition. [196][197][198] UV radiation primarily affects adaptive immunity, and has been used to induce and promote skin photocarcinogenesis, and to modulate the immune response in diverse experimental immunoinflammatory conditions of the skin.…”

“…[196][197][198] Effects vary with dose, duration of exposure and wavelength composition. [196][197][198] UV radiation primarily affects adaptive immunity, and has been used to induce and promote skin photocarcinogenesis, and to modulate the immune response in diverse experimental immunoinflammatory conditions of the skin. [196][197][198] Chemicals Experimental use of chemicals also has been and remains an important method to suppress or ablate immunity.…”

“…[196][197][198] UV radiation primarily affects adaptive immunity, and has been used to induce and promote skin photocarcinogenesis, and to modulate the immune response in diverse experimental immunoinflammatory conditions of the skin. [196][197][198] Chemicals Experimental use of chemicals also has been and remains an important method to suppress or ablate immunity. Examples including metals, aromatic hydrocarbons and other environmental contaminants, and antimicrobial agents are summarized in Table 4.…”

Ultraviolet B‐induced immunosuppression is not associated with receptor activator of nuclear factor kappa B ligand upregulation in human skin

“…To the Editor, Over the past 10 years, there has been significant progress in our understanding of the mechanisms by which UV induces immunosuppressive effects on the skin. 1 Several skin chromophores have been shown to absorb UV radiation including DNA, trans-urocanic acid, membrane phospholipids, 7-dehydrocholesterol, and tryptophan. 2 Following absorption of UV radiation by chromophores, a number of events are triggered including an increase in several cytokines such as IL-10 and IL-33, a decrease in IL-12, an increase in oxidative stress, clustering of cell surface receptors, a decrease in epidermal Langerhans cells, an increase in mast cells, and induction of regulatory T cells.…”