Daily very low UV dose exposure enhances adaptive immunity, compared with a single high‐dose exposure. Consequences for the control of a skin infection

Abstract

Ultraviolet radiation (UVr) promotes several well-known molecular changes, which may ultimately impact on health. Some of these effects are detrimental, like inflammation, carcinogenesis and immunosuppression. On the other hand, UVr also promotes vitamin D synthesis and other beneficial effects. We recently demonstrated that exposure to very low doses of UVr on four consecutive days [repetitive low UVd (rlUVd)] does not promote an inflammatory state, nor the recruitment of neutrophils or lymphocytes, as the exposure to a single high UV dose (shUVd) does. Moreover, rlUVd reinforce the epithelium by increasing antimicrobial peptides transcription and epidermal thickness. The aim of this study was to evaluate the adaptive immune response after shUVd and rlUVd, determining T-cell and B-cell responses. Finally, we challenged animals exposed to both irradiation procedures with Staphylococcus aureus to study the overall effects of both innate and adaptive immunity during a cutaneous infection. We observed, as expected, a marked suppression of T-cell and B-cell responses after exposure to an shUVd but a novel and significant increase in both specific responses after exposure to rlUVd. However, the control of the cutaneous S. aureus infection was defective in this last group, suggesting that responses against pathogens cannot be ruled out from isolated stimuli.

Assessment of Inflammation in 3D Reconstructed Human Skin Exposed to Combined Exposure to Ultraviolet and Wi-Fi Radiation

“…On the contrary, exposure to a single high UV dose does. Furthermore, they observed a marked suppression of T cell and B cell responses after the single high-dose exposure and an increase in both specific responses after exposure to repetitive low doses [59].…”

Perspectives on the FDA’s Sunscreen Policy: New Aging Theory, Sunlight Benefits, Enhanced Immunity, COVID-19 Mortality, Modelling Analyses, Melanoma Risks and Etiology

“…This subject has been well reviewed and only a few points will be highlighted. Although exposure to intense or burning sunlight is well known to be immunosuppressive, moderate sunlight may increase immune function and this may be partly related to enhanced synthesis of vitamin D, which has numerous potential health benefits [28][29][30][31][32][33][34][35][36]. Sunlight can increase production or release of nitric oxide that may dilate blood vessels, increase blood flow to tissues and enhance immunity, as well as to reduce blood pressure, heart attack and stroke; nitric oxide can be induced by solar UVA and UVB rays [29][30][31][32]37,38].…”

Sun Exposure and Melanoma, Certainties and Weaknesses of the Present Knowledge

“…Even more surprisingly, it was recently found that a history of sunny holidays, before CMM diagnosis, was associated with lower mean Breslow thickness ( 66 ) and intermittent or regular sun exposures, after CMM diagnosis, were associated with lower mean relapse rates ( 66 , 67 ). A possible explanation is that low/ physiologic doses of UVR inhibit the adaptive immune system but induce parts of the innate immune system ( 68 ). However, UVR effects on the presence and activity of innate immune system cells, e.g., macrophages, tumor associated macrophages (TAMs), dendritic cells (DCs), mast cells and NK cells remain to be explored ( 69 ).…”