TLR4 and vitiligo: In vitiligo-affected patients, RAGE, out of the three PRRs (pattern recognition receptors) that bind HMGB1 (the others being the toll-like receptors TLR2 and TLR4), is the only one upregulated, and its blockade significantly reduces the levels of IL-8 and CXCL16 [chemokine (C-X-C motif) ligand 16] in keratinocytes.