Investigating the Expression of LL-37 Antimicrobial Peptide in Autoimmune Bullous Disorders: Implications for Pemphigus

Objective: This study aimed to investigate the expression of the antimicrobial peptide cathelicidin LL-37 and discuss its role as a critical factor in developing pemphigus. Methods: The expression of LL-37 mRNA was assessed in individuals with pemphigus foliaceous (PF) and pemphigus vulgaris (PV) at different stages of the disease, in comparison to healthy controls (HCs), using RT-PCR and ELISA. The LL-37 expression profile was differentially dysregulated in pemphigus. Results: a high LL-37 expression level was shown in newly diagnosed patients compared to healthy controls. The short-term LL-37 gene expression follow-up showed a significant up-regulation after three months of cortical therapy treatment and a strong negative correlation with anti-Dsg1 Abs in PF-monitored patients, suggesting that LL-37 could be implicated in remission induction. In line with this hypothesis, the long-term follow-up results showed a significant increase in LL-37 expression according to disease severity when devising treated patients in the retrospective study, according to their PDAI. Conclusion: Our preliminary finding suggests that the timing and the cellular context change the expression of LL-37 according to the disease severity, which determines the direction of the cellular response. We propose this small peptide as a point of debate requiring deep investigations in pemphigus.