Involvement of granzyme B and granulysin in the cytotoxic response in lichen planus

Background: Lichen planus is an inflammatory dermatosisinvolving either skin and/or mucosal epithelial surfaces. A cell-mediated cytotoxicity response is the main suspected mechanism ofthis dermatosis. Granzyme B and granulysin are components of thecytoplasmic granules of cytotoxic T lymphocytes and natural killers.They are involved in cell-mediated apoptosis. This work studies thepossible implication of granzyme B and granulysin in the cell-mediatedcytotoxicity response in lichen planus.Methods: In situ expression of granzyme B and granulysin wasstudied by real-time reverse transcriptase polymerase chain reaction in15 biopsies of lichen planus. The distribution and the phenotype of theinflammatory infiltrate and the expression of granzyme B were studiedby immunohistochemistry in seven other biopsies of lichen planus.Results: Granzyme B and granulysin mRNA expression was one totwo hundred times greater than in biopsies of normal skin.Immunohistochemical study revealed that the lymphohistiocyticinfiltrate consisted mainly of CD41 and CD81 lymphocytes.Granzyme B1 cells were observed close to apoptotic keratinocytes.Conclusion: Our results suggest a central role for cell-mediatedcytotoxicity by the granule exocytosis pathway probably because ofauto-cytotoxic T-cell clones in the pathogenesis of lichen planus.Ammar M, Mokni M, Boubaker S, El Gaied A, Ben Osman A, LouzirH. Involvement of granzyme B and granulysin in the cytotoxicresponse in lichen planus.J Cutan Pathol 2008; 35: 630–634.