Role of mast cells in pathogenesis of oral lichen planus

Abstract

Recent attention has been directed toward the role of mast cells in the pathogenesis of oral lichen planus. Mast cells are responsible for trafficking inflammatory cells into the connective tissue that in turn helps in progression and maintenance of chronicity of oral lichen planus (OLP). OLP is a T-cell-mediated chronic inflammatory oral mucosal disease of unknown etiology, and lesions contain few B-cells or plasma cells and minimal deposits of immunoglobulin or complement. Hence, OLP is ideally positioned for the study of human T-cell-mediated inflammation and autoimmunity. This study was done to evaluate the mast cell count using toluidine blue stain in OLP and compares it with oral lichenoid reaction (OLR), and to propose the possible role of mast cells in the pathogenesis of OLP and OLR. Ten cases each of OLP and OLR and five cases of normal buccal mucosa were taken from the archives of Department of Oral Pathology. The samples were stained with toluidine blue using standard toluidine blue method by Wolman 1971. An increase in mast cell count was observed in OLP and OLR in comparison to normal oral mucosa. However, no significant differences in mast cell count were noted between OLP and OLR.

Keywords: Lichen planus; lichenoid reaction; mast cells.

Figure 1

(a) Photomicrograph showing mast cells in connective tissue of normal oral mucosa (4× toluidine blue stain). (b) Photomicrograph showing mast cells in subepithelial zone of lichen planus (10× toluidine blue stain)

Figure 2

Photomicrograph showing mast cells in deeper connective tissue of lichen planus (10× toluidine blue stain)

Figure 3

Degranulation of mast cells following T-cell interaction

Figure 4

Interaction of mast cells showing their bidirectional role in pathogenesis of OLP

Figure 5

Overall effect of mast cells in pathogenesis of OLP