Expression of Foxp3 and interleukin-17 in lichen planus lesions with emphasis on difference in oral and cutaneous variants

Foxp3 is a specific marker for regulatory T cells (Tregs), and interleukin (IL)-17 is the signature cytokine of T-helper (Th) 17 cells. Recent studies suggested that Foxp3+ Tregs and IL-17+ Th17 cells may be involved in pathogenesis of lichen planus (LP). The objectives of this study were to examine the immunoexpression of Foxp3 and IL-17 in archival paraffin-embedded biopsy specimens from 80 cases of LP (oral LP, n = 42; cutaneous LP, n = 38) and compare against normal control tissues (oral mucosa, n = 10; skin, n = 10). The results showed that the mean number of Foxp3 and IL-17 expression in LP was significantly higher compared to controls, respectively (both P < 0.001). A positive correlation between Foxp3 and IL-17 expression (r = 0.273; P = 0.014) was observed. Moreover, the mean number of Foxp3 expression in oral LP was significantly higher than cutaneous LP (P < 0.001). Collectively, our findings demonstrated the increased expression of Foxp3 and IL-17 in LP lesions including oral and cutaneous variants. Foxp3 expressing in oral LP was higher than cutaneous LP, which may be associated with the difference in clinical behaviour of the two variants of the disease. Further studies are required to investigate the immunopathologic mechanisms and therapeutic target of Foxp3+ Tregs and IL-17+ Th17 cells in LP.