Lymphocytes, neuropeptides, and genes involved in alopecia areata
J. Clin. Invest. Amos Gilhar, et al. 117:2019 doi:10.1172/JCI31942 [Go to this article.]

Figure 2
A model of immune privilege collapse in AA pathogenesis. Both a normal anagen (growing) hair follicle (A) and a hair follicle in AA (B) are shown. MHC class I molecules are expressed on the epidermis, and on the most superficial (distal) portion of the normal hair follicle epithelium. The inferior (proximal) portions of the hair follicle are immune privileged and deficient in expression of MHC classes I and II as well as APCs. By contrast, the AA anagen hair follicle expresses MHC class I and II molecules throughout the follicular epithelium, including the portion adjacent to the dermal papilla of the hair follicle. Active AA also exhibits a perifollicular infiltrate of CD4⁺ T cells and an intrafollicular infiltrate of CD8⁺ T cells. IRS, inner root sheath; ORS, outer root sheath.