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Author: Dr Jennifer Taylor, Dermatology Registrar, Waikato Hospital, Hamilton, New Zealand. DermNet New Zealand Editor in Chief: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy editor: Maria McGivern. April 2017.
Antimicrobial peptides are protein molecules of the innate immune system and are found in all organisms. They have potent broad-spectrum antimicrobial properties and help protect the body against infection.
There are over 100 antimicrobial peptides in the skin. The best characterised are:
Cathelicidins were the first AMPs discovered and are abundantly expressed in mast cells. The only human cathelicidin is LL-37 and is also known as cathelicidin antimicrobial peptide 18 kDa or CAP-18.
α-Defensins and β-defensins are widely distributed in epithelial cells and phagocytes in high concentrations.
Antimicrobial peptides are found in a variety of tissues throughout the body. In the skin, antimicrobial peptides are mainly produced by:
They are stored in lamellar bodies (secretory granules found within the layers of cells in the skin). Circulating immune cells, particularly neutrophils, also produce antimicrobial peptides.
Functions of antimicrobial peptides include:
Patients with atopic dermatitis (eczema) have decreased levels of antimicrobial peptides in their skin. Patients with atopic dermatitis are susceptible to:
There are increased levels of antimicrobial peptides in psoriasis plaques.
Rosacea is characterised by inflammation and vascular reactivity.
Understanding the molecular elements of antimicrobial peptides might lead to a better understanding of inflammatory skin disease and new treatments.
The anticancer properties of antimicrobial peptides are currently not well characterised, but there is speculation that antimicrobial peptides could lead to new treatments in the future.
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