Lichen planopilaris (LPP) is a rare alopecia disorder. The histopathological features of LPP may resemble discoid lupus erythematosus (DLE). However, LPP usually lacks interfollicular inflammation, which differentiates it from DLE. Methods: Skin biopsies were taken from subjects with early-stage LPP and DLE. The biopsies were evaluated for anti-CD56, anti-CD94, and anti-NKG2A/C/D-positive cells; the results were compared among two diseases. Results: Anti-CD4, -CD8, and -CD94 positive cells

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... y infiltrate the perifollicular dermis from the infundibulum to the hair isthmus in patients with LPP. Anti-CD56 and-NKG2C-positive cells were observed in the hair isthmus and bulge area (LPP) and in the infundibulum (DLE). In LPP, anti-NKG2A-positive cells were mostly seen in the infundibulum (p<0.05), but there were no significant differences in the number of anti-NKG2A-positive cells between the infundibulum, hair isthmus, or bulge area in subjects with DLE. Conclusions: Our results show differences in the localization of anti-NKG2A/C-positive cells between subjects with LPP and those with DLE. The inflammation in LPP initially originates in the hair isthmus and/or bulge followed by the interfollicular upper dermis. However, anti-NKG2A-positive cells prevent further enlargement of the inflammatory lesion in the interfollicular upper dermis of subjects with LPP. Keywords: Lichen palnopilaris (LPP); Natural killer group 2A (NKG2A); NKG2C; Discoid lupus erthematosus (DLE); DNAX activating protein of 12 kDa (DAP12)