Downregulation of integrin-αvβ6 on keratinocytes in the scar of lichen planopilaris and folliculitis decalvans: Relevance for the disappearance of epidermal Langerhans cells.

Primary cicatricial alopecia (PCA) is a group of poorly understood mechanisms in which the destruction of hair follicles leads to permanent hair loss. Lichen planopilaris (LPP) is a type of lymphocytic PCA and it has been known for epidermal Langerhans cells (LC) to disappear in the scar of LPP. We also found that epidermal LC also disappeared in the scar of folliculitis decalvans (FD), a type of neutrophilic PCA. Of note was that epidermal LC did not disappear in the scar of discoid lupus erythematosus, another type of lymphocytic PCA, suggesting that LC disappearance in the scar was not always a common feature of PCA. We found that the expression of integrin (ITG)-αvβ6 in scar epidermis was significantly diminished in LPP and FD, but not in other PCA and disorders accompanied with scar formation. We also found that exogenous interleukin-1β and α-interferon downregulated ITG-αvβ6 expression in normal human epidermal keratinocytes. These data suggest that downregulation of ITG-αvβ6 may be one of the causes of LC disappearance in the scar of LPP and FD.