BACKGROUND: Antimicrobial peptides (AMPs) are small effector molecules of the innate immune system with well-known antimicrobial activity. Skin infections rarely occur in patients with cutaneous lupus erythematosus (CLE), and AMP expression in CLE has not been previously evaluated.
OBJECTIVES: We aimed to determine the expression of several important AMPs in 3 different subtypes of CLE.
METHODS: Skin lesions were analyzed for the gene and protein expression of human β-defensin (hBD)-1, -2, and -3; RNase-7; the cathelicidin LL-37; and psoriasin (S100A7) using real-time reverse transcriptase polymerase chain reaction and immunohistochemistry.
RESULTS: Skin biopsy specimens of 96 study participants including 47 patients with CLE (15 patients with discoid lupus erythematosus [LE], 11 patients with subacute CLE, and 21 patients with LE tumidus), 34 patients with psoriasis, and 15 healthy control subjects were evaluated in this study. HBD-2, hBD-3, LL-37, and psoriasin were significantly more highly expressed in CLE as compared with healthy controls, and most AMPs were significantly more highly induced in subacute CLE as compared with discoid LE and LE tumidus. AMP gene expression paralleled well with AMP protein expression in CLE and controls. Subacute CLE and discoid LE showed a similar correlation of AMP gene expression (significant correlations between hBD-1 and RNase-7, hBD-2 and hBD-3, hBD-2 and psoriasin, and hBD-3 and psoriasin).
LIMITATIONS: The relatively small number of samples and the lack of analysis of the lesional bacterial colonization are a limitation.
CONCLUSIONS: Several AMPs are increased in CLE at both gene and protein levels. This could explain the low prevalence of skin infections in CLE. It remains to be elucidated whether AMPs play a pathogenic role in CLE.