Immunofluorescent analysis of the basement membrane zone in lichen planus suggests destruction of the lamina lucida in bullous lesions

Basement membrane changes in lichen planopilaris

BACKGROUND

Lichen planopilaris (LPP) is an inflammatory disease that affects the scalp and tends to produce cicatricial alopecia. The inflammatory process frequently results in the disruption of the basal cell of the external root sheath of the hair follicle.

OBJECTIVES

To investigate the alterations in the basement membrane zone (BMZ) in LPP by immunohistochemistry.

METHODS

Skin biopsies from six patients with LPP plus six normal controls were studied by immunohistochemistry with antibodies to the following BMZ components: cytokeratin 5, cytokeratin 14, BP230 (bullous pemphigoid), BP180, plectin, laminin 5, collagen IV and collagen VII.

RESULTS

The localization and staining of the hemidesmosome, laminin and collagen components were strikingly different in the inflamed follicular epithelium when compared to the uninvolved follicles or interfollicular epithelium in active LPP lesions. The hemidesmosome-associated complexes were weakly expressed and discontinuous in involved hair follicles. The expression of laminin-5, type IV collagen and type VII collagen was disrupted and not linear along the BMZ with finger-like projections of the staining protruding into the dermis. The expression of the intermediate filaments was normal.

CONCLUSION

These alterations in the BMZ in LPP may explain the abnormal healing at follicular level which leads to irreversible hair loss and scarring in this condition.

Lichen planus

Lichen Planus is a relatively common inflammatory dermatosis of unknown origin. The present review summarizes the histological and clinical features of lichen planus and variants, including lichenoid drug reactions, are described. Possible mechanisms of pathogenesis of lichen planus are reviewed. The development of malignancy in association with lichen planus and the association with hepatitis are discussed. Treatment options for the more difficult manifestations of lichen planus are proposed.

Epitope spreading: lessons from autoimmune skin diseases

Autoimmune diseases are initiated when patients develop aberrant T and/or B cell responses against self proteins. These responses presumably are directed to single immunogenic epitopes on these proteins. Recent data in animal models of autoimmune diseases suggest that the targets of immune responses in autoimmunity do not remain fixed, but can be extended to include other epitopes on the same protein or other proteins in the same tissue, a phenomenon termed "epitope spreading." The "epitope spreading" phenomenon also applies to situations in which tissue damage from a primary inflammatory process causes the release and exposure of a previously "sequestered" antigen, leading to a secondary autoimmune response against the newly released antigen. In experimental autoimmune animal diseases, "epitope spreading" seems to have significant physiologic importance in determining the course and duration of disease. In this paper, we review the current concepts in animal models of autoimmune diseases in order to define the "epitope spreading" phenomenon, and we then propose how this phenomenon might play a significant role in the development and the course of autoimmune skin diseases. Hopefully, an understanding of "epitope spreading" will help the dermatology community to better understand the pathogenesis of autoimmune skin diseases and to rationally fashion disease-specific immune therapy in the future.

Destruction of the epithelial anchoring system in lichen planus

To find out whether the epithelial anchoring system shows any alterations in lichen planus, we examined the distribution of type VII collagen, alpha 6 beta 4 integrin, and kalinin in lesions of lichen planus. These molecules were chosen because they are structural components of anchoring fibrils, hemidesmosome-associated complexes, and anchoring filaments. The localization of type VII collagen in lichen planus was strikingly different from that in nonaffected mucosa or dermis or in other mucocutaneous lesions. In the normal mucosa, type VII collagen was localized only at the basement membrane zone. In lichen planus, type VII collagen was present not only in the basement membrane area but also in streaked patterns deep in the connective tissue. The hemidesmosome-associated complex, alpha 6 beta 4 integrin, was localized at the basal aspect of basal epithelial cells of nonaffected sites, but was diffuse and discontinuous in lichen planus lesions. Most of the basal keratinocytes, however, stained for this integrin. Kalinin staining was discontinuous in lichen planus lesions. Often, finger-like projections of kalinin staining were found protruding into the connective tissue stroma. Kalinin was localized at the basement membrane zone of the nonaffected tissue and other mucocutaneous lesions. These results indicate that in cutaneous and mucosal lichen planus, the epithelial anchoring system is disturbed.