Increased Serum Level and High Tissue Immunoexpression of Interleukin 17 in Cutaneous Lichen Planus: A Novel Therapeutic Target for Recalcitrant Cases?

Abstract

Background: Interleukin-17 is supposed to play an important role in the pathogenesis of oral lichen planus (OLP). However, there is scarce data in the literature on its significance in the cutaneous variant of the disease.

Objectives: To determine the serum level and tissue immunoexpression of IL-17 in cutaneous lichen planus (CLP).

Methods: Fifty-two adult patients with CLP, without any significant autoimmune or inflammatory conditions, were included in the first part of the study. The control group consisted of 27 age- and sex-matched healthy volunteers. Serum concentration of IL-17 was quantified using enzyme-linked immunosorbent assay (ELISA) kit. In the second part of the study, the tissue expression of IL-17 was assessed in archival paraffin-embedded biopsy specimens from CLP (n = 14) against normal control tissues (n = 11) using immunohistochemical assays. The expression was evaluated using Zeiss Axio Imager A2 light microscope. Positively stained cells were counted in 10 fields of view for biopsy specimen at 200x magnification, and the mean value was calculated.

Results: The serum level of IL-17 was significantly elevated in patients with CLP, compared with healthy volunteers (0.218 ± 0.221 ng/ml versus 0.126 ± 0.058 ng/ml, respectively; p = 0.025). No correlation was found between the serum concentration of IL-17 and patient age, gender, disease duration, extent of skin involvement, the presence or intensity of pruritus, and coexistence of mucosal lesions. In tissue samples from CLP lesions, significantly higher numbers of cells expressing IL-17 were found when compared to a healthy skin (p < 0.001).

Conclusion: Elevated serum concentration of IL-17 and high expression in a lesional skin support the hypothesis that IL-17 is implicated in the immunopathogenesis of CLP. These findings may constitute a premise for the future use of anti-IL-17 monoclonal antibodies in the treatment of severe and recalcitrant forms of CLP.

Figure 1

Increased serum level of IL-17 in patients with CLP compared to controls (p = 0.025).

Figure 2

Representative immunohistochemical stainings of IL-17 expression: (a) high number of cells showing positive staining in CLP lesions and (b) single cells showing positive staining in a healthy skin. Magnification, ×200.

Figure 3

Increased number of cells expressing IL-17 in CLP lesions compared to a healthy skin (p < 0.001).