Detection of fascin and CCR-7 positive mature dendritic cells in oral lichen planus

Background: Dendritic cells (DC) play a crucial role in the pathogenesis of oral lichen planus (OLP) with respect to antigens presented to T cells. We performed immunohistochemical analysis to elucidate the process of activation of DC in OLP. Methods: Thirty biopsy specimens were obtained from the patients with OLP. The expressions of CD1a, Langerin, S‐100, fascin, chemokine receptor‐7 (CCR‐7), D2‐40, cyclooxygenase‐2 (COX‐2), and microsomal prostaglandin E synthase‐1 (mPGES‐1) in DC from OLP and disease free control were investigated using specific antibodies. The distribution and number (1 mm2) of DC were assessed in the intra‐epithelium and the submucosa specimens. Correlation between the number of DC and epithelium thickness was also determined. Result: Immature DC (Langerin+, CD1a+, and S‐100+) were identified in the epithelia from OLP patients and control, though the numbers of Langerin+ and CD1a+ positive cells were decreased in the OLP samples as compared to the control. Mature DC (fascin+) were identified in the submucosa specimens, not found in the epithelium from OLP or control. Double immunostaining revealed DC positive for fascin and CCR‐7 in the submucosa, which had migrated into D2‐40+ lymph vessels. Furthermore, keratinocytes expressed both Prostaglandin E2 (PGE2) converting enzymes, COX‐2, and mPGES‐1, indicating PGE2 synthesis in the epithelial layer of the OLP specimens. Conclusion: Our results indicate that DC change from immature to mature in the epithelium and are then drawn out to the submucosa. We demonstrate that mature DC localized in the submucosa, it consequently migrates into lymph vessels. This maturation process of DC is an important immunopathological feature of OLP.