Recent Advances in the Pathogenesis of Autoimmune Hair Loss Disease Alopecia Areata

Table 1

The mechanism of HF immune privilege.

(i) Absent or barely detectable expression of MHC class I.
(ii) Hair follicular melanocytes of the human anagen scalp are MHC class I-negative.
(iii) Downregulation of the MHC class I pathway-related molecules 𝛽2-microglobulin and transportation of antigen processing-2 (TAP-2).
(iv) Downregulation of interferon regulatory factor-1 expression.
(v) Upregulation of immunosuppressive factors such as TGF-𝛽1 and TGF-𝛽2, ACTH, and α-MSH.
(vi) Absence of MHC class II+ or NLDC-145+ Langerhans cells.
(vii) Sparse distribution of NK cells and CD4+ and CD8+ T cells.
(viii) Absence of lymphatics.