Background/Purpose Langerhans cells (LCs) are antigen presenting cells. This study assessed the LC counts in oral epithelial dysplasia (OED) and their correlation to clinicopathological parameters. Methods This study examined the LC counts in the epithelia and subepithelial connective tissues of 58 patients with OED (21 mild, 18 moderate, and 19 severe OED lesions) and 10 specimens of normal oral mucosa (NOM) by anti-S-100 protein immunostaining. Results We found that the mean LC counts in the epithelia or subepithelial connective tissues increased significantly from NOM samples through mild and moderate OED to severe OED samples. In addition, a significant correlation was found between higher mean LC counts in the dysplastic epithelia of OED samples and OED lesions with thicker epithelial layers (p < 0.001) or wider inflammatory zones (p < 0.001), and between higher mean LC counts in the subepithelial connective tissues of OED samples and OED lesions with wider inflammatory zones (p < 0.001). Moreover, the nine OED lesions with malignant transformation had a significantly lower mean LC count than the 49 OED lesions without malignant transformation. Conclusion The significant and gradual elevation in LC count from NOM through mild and moderate OED to severe OED lesions suggests an upregulation of immunosurveillance ability in OED patients during the early oral carcinogenesis process. A low LC count in OED lesions may suggest the partial loss of immunosurveillance ability against dysplastic cells; this in turn favors the malignant transformation of an OED lesion into oral cancer.
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