The peptide LL‑37, made by skin cells, can either be too low or too high and this imbalance contributes to common skin problems like eczema, rosacea, and psoriasis. Low LL‑37 makes eczema skin prone to infections, while too much or broken‑down LL‑37 fuels inflammation in rosacea and helps trigger an autoimmune reaction in psoriasis. Targeting LL‑37 levels could become a way to treat these conditions, but the study doesn’t give specific how‑to steps.

Keratinocytes produce and secrete antimicrobial peptides which function as endogenous antibiotics and as signaling molecules within the cutaneous innate immune system. Recent studies demonstrate that the antimicrobial peptide cathelicidin LL-37 plays an important role in the pathogenesis of atopic eczema, rosacea and psoriasis. Whereas skin in atopic eczema shows decreased cathelicidin expression which leads to increased susceptibility to superinfection in those patients, overabundant expression of cathelicidin peptide fragments causes inflammation in rosacea. Finally, in psoriasis cathelicidin peptide binds to self DNA which triggers an autoimmune response. These studies demonstrate the role of cathelicidin as a central factor in the pathogenesis of cutaneous inflammation. Therapies targeting cathelicidin expression and function could lead to new treatments for these diseases.