Advances in Alopecia Areata

Immune Privilege

Immune privilege occurs at defined tissue compartments (e.g., anterior chamber of the eye, testis, blood-brain barrier, placenta) and are essential for normal organ function¹

Immune privilege is established by complex mechanisms that suppress inflammation and promote immune tolerance²

Certain areas of the hair follicle are immune privileged sites:

Hair bulge, which contains hair follicle stem cells³
Hair bulb during the anagen phase only⁴

It is hypothesized that the purpose of immune privilege in the hair follicle is to prevent anagen- and/or melanogenesis-associated autoantigens from immune recognition by autoreactive CD8+ T cells¹

Functional studies suggest that CD8+ NKG2D+ T cells are the major effectors in alopecia areata pathogenesis5

Functional studies suggest that CD8+ NKG2D+ T cells are the major effectors in alopecia areata pathogenesis⁵

Hair follicles that lose their immune privilege during the anagen phase are targeted by CD8+ T and NKG2D+ cells6

Hair follicles that lose their immune privilege during the anagen phase are targeted by CD8+ T and NKG2D+ cells⁶

Loss of hair follicle immune privilege in the anagen hair bulb is accepted as a key attribute in alopecia areata pathogenesis4

Loss of hair follicle immune privilege in the anagen hair bulb is accepted as a key attribute in alopecia areata pathogenesis⁴

References

Paus R, Ito N, Takigawa M, Ito T. The hair follicle and immune privilege. Review J Investig Dermatol Symp Proc. 2003;8(2):188-194. doi:10.1046/j.1087-0024.2003.00807.x
Hong S, Van Kaer L. Immune privilege: keeping an eye on natural killer T cells. J Exp Med. 1999;190(9):1197-200. doi:10.1084/jem.190.9.1197
Azzawi S, Penzi LR, Senna MM. Immune privilege collapse and alopecia development: is stress a factor? Skin Appendage Disord. 2018;4(4):236-244. doi:10.1159/000485080
Paus R, Bulfone-Paus S, Bertolini M. Hair follicle immune privilege revisited: the key to alopecia areata management. J Investig Dermatol Symp Proc. 2018;19(1):S12-S17. doi:10.1016/j.jisp.2017.10.014
Pratt CH, King LE Jr, Messenger AG, Christiano AM, Sundberg JP. Alopecia areata. Nat Rev Dis Primers. 2017;3:17011. doi:10.1038/nrdp.2017.11
Paus R, Bertolini M. The role of hair follicle immune privilege collapse in alopecia areata: status and perspectives. J Investig Dermatol Symp Proc. 2013;16(1):S25–S27. doi:10.1038/jidsymp.2013.7

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Immune Privilege

Chapter 2: Mechanism of Disease of Alopecia Areata

References

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Immune Privilege

Related Resources

Chapter 2: Mechanism of Disease of Alopecia Areata

References

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