In Human Skin, UVB Initiates Early Induction of IL-10 Over IL-12 Preferentially in the Expanding Dermal Monocytic/Macrophagic Population

The study demonstrated that after UVB exposure, differentiated macrophages in human skin produced high levels of IL-10 and low levels of IL-12, unlike Langerhans cells which produce IL-12. The first significant rise in IL-10 mRNA in the dermal CD11b+ monocytic/macrophagic population occurred 6 hours post-UV, peaking at 24-48 hours, and was followed by intense IL-10 production in the epidermis at 72 hours. This suggests that UV-induced changes in the dermal microenvironment activate these macrophages, leading to their migration to the epidermis. The findings highlighted the role of IL-10 in UV-induced immunosuppression and the dynamic changes in skin immune cell populations post-UV exposure.