Immune Privilege Collapse and Alopecia Development: Is Stress a Factor

Abstract

Hair is a defining mammalian feature that serves as a hallmark of human communication. Given the critical significance of hair in social, religious, and political contexts, it is important to understand factors that play a role in hair loss disorders. The hair follicle is an immune privileged site, and mounting evidence suggests that the collapse of immune privilege contributes to the pathogenesis of autoimmune hair loss disorders, including alopecia areata and lichen planopilaris. This review comprehensively appraises the current literature to shed light on mechanisms for immune privilege collapse, and examines the role of neurogenic stress in triggering this process.

Alopecia areata: a review of disease pathogenesis

“…MICA‐positive cells, aside from their MHC presentation state, become visible to NKG2D receptors on NK cells, causing activation of the innate immune system and the cascade of events following it . The stressed environment could also downregulate IP guardians and MIF . These factors were shown to correlate negatively with IFN production, NK cell accumulation and, most importantly, MHC presentation.…”

“…9,49 The stressed environment could also downregulate IP guardians and MIF. 25,82 These factors were shown to correlate negatively with IFN production, NK cell accumulation and, most importantly, MHC presentation. When HF cells begin to present MHC-I molecules, a vast group of secured antigens becomes visible to the immune system and subsequent immunological events thereafter become unstoppable.…”

Les lymphocytes T régulateurs contrôlent la croissance du poil et préviennent le développement de la pelade

“…En effet, une accumulation de LTreg activés (CD25 + , CTLA-4 + , ICOS + ) au niveau du follicule pileux télogène semble nécessaire pour la transition de la phase télogène à la phase anagène. Par ailleurs, la déplétion immunosuppresseurs, la présence de LTreg et de cellules dendritiques tolérogènes [3,4]. L'accumulation de LTreg activés exprimant Jagged 1, au niveau du follicule en phase télogène permet la prolifération et la différenciation des HFSC via la voie Notch, favorisant ainsi l'entrée en phase anagène [6].…”

“…[3]. Par ailleurs, le système immunitaire au niveau du follicule a une double fonction : (1) il est dans un état d'immuno-modulation prévenant toute réponse inflammatoire ou auto-immune vis-à-vis d'un auto-antigène exprimé dans le follicule pileux sain [3,4] ; (2) il participe à la régulation du cycle pilaire ; en effet, selon la phase dans laquelle se trouve le poil, des acteurs de l'immunité innée et adaptative sont recrutés et sécrètent des médiateurs modulant l'avancée du cycle pilaire [5]. Cette double fonction semble reposer sur les lymphocytes T régulateurs (LTreg) dont un rôle dans le processus de régénération du poil a récemment été identifié [6,7].…”

Efficacy of Postbiotics in a PRP-Like Cosmetic Product for the Treatment of Alopecia Area Celsi: A Randomized Double-Blinded Parallel-Group Study

“…An incidence of [ 2% among the general population has been reported, with a lifetime risk of 1.7% for both men and women [3]. AA is mainly related to genetic, autoimmunity and inflammatory factors [4,5], with the collapse of the immune privilege of the hair follicle reported to play a pivotal role in the pathogenesis of this autoimmune disorder [6].…”