Expression of antimicrobial peptides in atopic dermatitis and possible immunoregulatory functions.

PURPOSE OF REVIEW: To summarize the findings on the expression of antimicrobial peptides in the skin in inflammatory skin diseases and particularly in atopic dermatitis. Moreover, the literature addressing the functions of antimicrobial peptides (AMPs) beyond antimicrobial activities with impact on allergic skin inflammation is summarized as well. RECENT FINDINGS: Although lower expressed than in psoriasis, most AMPs have been shown to be either constitutively expressed or upregulated in atopic dermatitis as well. A number of immunoregulatory functions which might impact on allergic skin inflammation have been described for several antimicrobial peptides, mainly for human β-defensins and the cathelicidin LL-37. SUMMARY: From the recent literature, there is considerable evidence that AMPs are induced in the skin in atopic dermatitis. However, some studies suggest that the induction, release or mobilization of some AMPs in atopic dermatitis may not reach sufficient levels to provide adequate control of cutaneous microbial colonization. Th2 cytokines appear to negatively influence the expression and induction of some AMPs. A number of immunoregulatory functions have been described for several AMPs. Most of them point to a proinflammatory function of AMPs in addition to their antimicrobial activities. Further studies are needed to clarify the role of AMPs in atopic dermatitis.