Immunohistologic analysis of epithelial cell populations in oral lichen planus

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.