EXPRESSION OF FETAL CYTOKERATINS IN EPIDERMAL-CELLS AND COLLOID BODIES IN LICHEN-PLANUS

Clusters of immunoglobulin (Ig)-coated colloid bodies (CBs) in the der mo-epidermal zone are a typical immunohistochemical feature in lichen planus (LP)-lesions. They are considered to rep resent dyskeratotic ba sal keratinocytes, yet their composition has not been completely eluci dated. In the present study skin biopsies of 10 LP-lesions, 3 other de rmatoses, and 10 biopsies of normal skin were studied immunohistochemi cally using monoclonal antibodies (MAbs) against fetal and differentia ted epidermal antigens. CBs were identified by FITC-anti-Ig. Binding o f MAb was visualized by double staining technique. Cytokeratin (CK) 10 /11, a marker of epidermal differentiation, was consistently detected in suprabasal keratinocytes and also in up to 95% of Ig-positive CBs i n LP. CK10/11 was additionally detected in basal keratinocytes in 9 LP -lesions, but not in normal skin. The basal cell-specific MAb BL7 stai ned basal layer keratinocytes in all biopsies. In contrast to normal s kin, in LP scattered suprabasal keratinocytes and CBs were also positi ve for BL7 in 10 and 7 cases, respectively. While fetal cytokeratins ( CK13 and CK8/18) were completely absent in control skin specimens, bot h cytokeratins were detected in various numbers of keratinocytes and C Bs in all LP-lesions. Our results support the hypothesis of an epiderm al origin of CBs. The cytokeratin profile seems to be severely disturb ed in LP. This includes both accelerated differentiation by the expres sion of suprabasal CK10/11 in basal keratinocytes and dedifferentiatio n by the expression of fetal epidermal antigens (CK13 and CK8/18). It is tempting to speculate that the observed alterations may triger T-ce ll activation and inflammatory onset in LP.