The nonkeratinocyte intraepithelial cell population in lichen planus. An ultrastructural characterization of cells in gingival lesions.

Lesions of gingival lichen planus were studied ultrastructurally to determine the types of cells, other than keratinocytes, present within the epithelial layer and the relationship of these cells to each other and to the keratinocytes. Cell types identified included small and medium-sized lymphocytes, macrophages, mast cells, and Langerhans cells. Some cells lacked sufficient specific features to permit definitive identification. The cells were found either singly or in groups. Generally, some alteration in the intercellular spaces between keratinocytes was apparent, even in regions where the mononuclear cells were absent or in the process of crossing the basal lamina. Most of the mononuclear cells had cytologic features which indicated that they were active cells. Occasionally lymphocytes appeared, on a morphologic basis, to be interacting with adjacent keratinocytes.