Daily exposures to UV radiation modulate the immune system increasing the cellular and humoral responses

CELA EM; FRIEDRICH AD; PAZ ML; LEONI J; GONZALEZ MAGLIO DH

Córdoba

Congreso; XVII International Congress of Photobiology; 2014

Over last decades, it has been widely studied the immunomodulatory effects of solar ultraviolet radiation (UVr) on the immune system. Even though UV exposure can lead to immunosuppression and photocarcinogenesis, it has also been attributed beneficial effects, mainly related to VitD synthesis. We aimed to compare two UVr exposures: a single high UV dose (SHUVD - 400 mJ/cm2), simulating a harmful exposure, versus repetitive low UV doses (LRUVD - 4 consecutive days, 20 mJ/cm2), simulating daily exposures. The modulation of immune response was evaluated by contact hypersensitivity reaction (CHS) to Oxazolone (OXA) and humoral response to tetanus toxoid (TT) challenge. CHS: SKH:1 hairless mice were UV-irradiated on their back without exposing the ears. Then, 24 hs or 8 days after the corresponding irradiation, mice were sensitized on the abdomens with OXA3%. Six days later, ears thickness were measured and animals were challenged in the ears with OXA 1%. Twenty four hours later, sensitized and naïve ears were measured. TT challenge: 24 hs or 8 days after the corresponding irradiation, mice were inoculated subcutaneously with a commercial TT vaccine. Three weeks later, mice were bled and serum antibodies isotypes (total IgG, IgG1, IgG2a, IgG2b, IgG3, IgM and IgA) were titrated. As it has been reported before, 24 hs after a SHUVD there was a reduction in CHS response and diminish in IgGT titer, accordingly to an immunosuppressive state. Surprisingly, 24 hs and 8 days after RLUVD we found an increase in CHS response and higher IgGT, IgG1 and IgG3 titers in serum than controls. Our results support the idea that harmful exposures to UVr should be avoided. However, we should not avoid completely the exposure to the Sun. Daily exposures may not only be necessary for vitamin D synthesis, but also to reinforce the immune system.