Immunohistologic analysis of epithelial cell populations in oral lichen planus

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Abstract
Previous studies have demonstrated heterogeneity within lesional lymphocytes in drug‐related oral lichen planus (D‐LP) and idiopathic lichen planus (I‐LP). This study examined the phenotype of Langerhans cells (LC) and keratinocytes in non‐erosive D‐LP and I‐LP. In I‐LP, keratinocytes expressed HLA‐DR antigens whilst LC co‐expressed CDIa, MHC Class II and CD4 antigens. The high levels of expression of MHC Class II antigens by LC were maintained during short term organ culture. In I‐LP, the epithelium contained occasional CD25 + dendritic cells (putative activated LC). These cell phenotypes are suggestive of cell activation and likely result from local production of gamma interferon. In D‐LP, expression of MHC Class II antigens on LC was reduced and no CD25+ cells were detected. The epithelium contained an increased number of CD45RA+ dendritic cells. While no differences between the production of interleukin‐1 and interleukin‐1 inhibitors by tissue samples could be detected, it is likely that the variations in epithelial cell phenotypes in I‐LP and D‐LP reflect altered cytokine production.