CONICET | Buscador de Institutos y Recursos Humanos

Ultraviolet radiation (UVr) promotes very well-known alterations on immune system, decreasing specific T cell responses among other effects. This deficient T cell response allow tumor skin cells to establish and grow, generating a tumor. Probiotics have been employed since ancient times, to positivelymodulateimmune responses, not only in the gastrointestinal tract but also in cutaneous tissue. As an example, probiotics have been successfully employed in the treatment of atopic dermatitis.In our laboratory, we have demonstrated that lipoteichoic acid (LTA) isolated from Lactobacillus rhamnosus GG is able to reduce the multiplicity and to delay the onset of Squamous Cell Carcinomas (SCC) in chronically UV-exposed mice, when administered orally all along the chronic irradiation schedule. In the present work, we aim to understand the mechanisms that may explain the observed anti-tumoral effect of orally administered LTA.In first place, we analysed the activation of gut-associated lymphoid tissue immune cells, in control and LTA-treated mice. We observed increments in the transcription of IL1βand IL-10 12h after treatment in the gut, TNF-α and IL-12p35 24h after treatment in Peyer?s patches (PP) and IFN-γ 48h after treatment in mesenteric lymph nodes (MLN). Moreover, an increase in the percentage of activated dendritic cells was observed in MLN. Secondly, we studied the oral LTA capacity to modulate UV-induced immunosuppression. We performed 8 administrations of LTA or PBS each other day to C57/BL6 mice, prior to 3 exposures to 150 mJ/cm2 of UVr. Twenty-four hours later, we sensitised animals with oxazolone, including a non-irradiated group used as control. Mice were challenged in the ear 6 days later, to observe the T cells-triggered inflammation. UVr significantly decreased inflammation, while LTA-treatment restored normal inflammatory response (p

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