Langerhans cells expressing HLA-DQ, HLA-DR and T6 antigens in normal oral mucosa and lichen planus

We compared Langerhans cells (LC) expressing HLA-DQ, HLA-DR and T6 antigens in biopsies from the same oral mucosal site in 12 patients with oral lichen planus and eight healthy volunteers. LC expressing each antigen were observed in all the specimens, but in lichen planus the cells were located in higher levels of the epithelium than in controls. Compared with controls, lichen planus contained significantly more HLA-DQ-positive LC (P = 0.04) and fewer HLA-DR-positive LC (P = 0.05), but there was no such difference in T6-positive LC. In lichen planus specimens, there were significantly more LC expressing HLA-DQ and T6 than HLA-DR (P = 0.0001 and 0.02 respectively); no such differences were found in normal mucosa. Epithelial cells in lichen planus expressed HLA-DR antigen, but not HLA-DQ or T6 antigens. We conclude that in lichen planus there is modulation of HLA-DR and HLA-DQ antigen expression by LC, or differences in the number of LC expressing those antigens.