INTRODUCTIONHuman melanocytes produce melanin, a pigment that protects the skin against damage from ultraviolet (UV) radiation. While pigment production is their main function, melanocytes also play roles in the skin's immune response and in cellular secretion. Within the innate immune system, pathogen identification is mediated by pattern‐recognition receptors, such as the Toll‐like receptors (TLRs). These receptors transduce signals that lead to NF‐κB activation, subsequently inducing the expressions of several pro‐inflammatory cytokines and chemokines. In humans, over 10 TLRs recognize distinct microbial ligands.The skin acts as a permeable physical barrier to external environmental stressors, playing an important role as the first defense against cutaneous microbial invasion. Many studies report TLRs expression and functions in keratinocytes. Human melanocytes are known to express TLR2, TLR3, TLR4, TLR7, and TLR9, but their functions are not known well. Human melanocytes also express the functionally active lipopolysaccharide (LPS) receptor proteins TLR4 and CD14. Prior studies have mainly focused on the roles of TLRs in melanogenesis. Upon activation, the TLR2 and TLR4 pathways increase pigmentation and activate TLR5, while the TLR7 pathway decreases pigmentation in human melanocytes.The effects of ultraviolet (UV) radiation on skin include increased pigmentation, inflammation, immunosuppression, and carcinogenesis. Upon exposure to UV radiation,
Photodermatology, Photoimmunology & Photomedicine – Wiley
Published: Jan 1, 2018
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