KLK5 and rosacea: The intradermal injection of LL37 is a classic method to induce a rosacea mouse model.[6] TLR2, which is highly expressed by keratinocytes in the skin lesions of rosacea patients, can increase the expression of LL37 by promoting the synthesis and activity of KLK5.[19] TLRs can be expressed on the surface of keratinocytes and macrophages.