TLR2 and Erythema: Innate immune activation leads to upregulation of keratinocyte-derived toll-like receptor 2 (TLR2) promoting the expression of the antimicrobial peptide cathelicidin, which is subsequently activated to bioactive LL-37 by kallikrein 5 (KLK-5) protease, leading to erythema and angiogenesis28.