Maintenance of hair follicle immune privilege is linked to prevention of NK cell attack

Taisuke Ito, Natsuho Ito, Matthias Saatoff, Hideo Hashizume, Hidekazu Fukamizu, Brian J. Nickoloff, Masahiro Takigawa, Ralf Paus

Research output: Contribution to journalArticlepeer-review

177 Scopus citations


Hair follicles (HFs) enjoy a relative immune privilege (IP) that is characterized by downregulation of major histocompatibility complex (MHC) class I and local expression of potent immunosuppressants. Normally, natural killer (NK) cells attack cells with absent/low MHC class I expression. However, because few perifollicular NK cells are found around healthy human anagen HFs, we asked how HFs escape from NK cell attack. This study suggests that this happens via an active NK cell suppression. Alopecia areata (AA), an organ-specific autoimmune disease thought to result from a collapse of HF-IP, in contrast, shows striking defects in NK cell inhibition/containment. We show that the NK cell inhibitor macrophage migration inhibitory factor is strongly expressed by the HF epithelium, and very few CD56+/NKG2D+ NK cells are observed in and around normal anagen HFs compared to AA with prominent aggregations of CD56+/NKG2D+ NK around AA-HFs. By flow cytometry, many fewer NK function-activating receptors (NKG2D, NKG2C) and significantly more killer cell Ig-like receptors-2D2/2D3 were found to be expressed on peripheral blood CD56+ NK cells of healthy controls than on those of AA patients. In addition, only weak immunoreactivity for MHC class I chain-related A gene was observed in normal anagen HFs compared to AA. To our knowledge, this defect is previously unreported and must be taken into account in AA pathogenesis and its management.

Original languageEnglish (US)
Pages (from-to)1196-1206
Number of pages11
JournalJournal of Investigative Dermatology
Issue number5
StatePublished - May 2008
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Dermatology
  • Cell Biology


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