Fas/FasL pathway is the main mechanism of CD8-induced cytotoxicity in cutaneous lichen planus

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Abstract

Background

Lichen planus (LP) is an inflammatory dermatosis involving either the skin and/or the mucosal epithelial surfaces. Apoptosis of keratinocytes by cluster of differentiation (CD) 8+ T cells may be mediated by the release of cytotoxic molecules such as perforin and granzyme B or by the Fas/Fas ligand (FasL) system.

Objective

To evaluate the degree of expression of both Fas/FasL and granzyme B in CD8+ infiltrating cells in lichen planus.

Patients and methods

Skin biopsies were taken from lesional skin of LP patients and from normal skin of normal control individuals. Immunofluorescence staining of CD8 with Fas/FasL or granzyme B (double markers) as well as TUNEL assay were performed.

Results

Immunofluorescence staining showed that CD8+ cells were strongly represented in the dermal infiltrate of LP patients. The difference in the mean number of FasL+ CD8+ cells between LP patients and healthy controls was significant (P=0.013), whereas the difference for granzyme B was not significant (P=0.11). Although apoptotic cells were significantly higher in LP patients (P=0.031), there was no significant correlation between FasL expression and the number of these apoptotic keratinocytes in the lesions. Comparison within the LP group revealed significant difference between FasL+ CD8+ cells and granzyme B+ CD8+ cells in LP dermal infiltrate (P=0.002).

Conclusion

The Fas/FasL pathway has the upper hand over the perforin/granzyme pathway in CD8+-mediated cytotoxicity in cutaneous LP.

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