Melnik BC, John SM, Chen W, Plewig G. T helper 17 cell/regulatory T-cell imbalance in hidradenitis suppurativa/acne inversa: the link to hair follicle dissection, obesity, smoking and autoimmune comorbidities.
Br J Dermatol 2018;
179:260-272. [PMID:
29573406 DOI:
10.1111/bjd.16561]
[Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/08/2018] [Indexed: 12/18/2022]
Abstract
BACKGROUND
Disintegration of the infundibula of terminal hair follicles (HFs) in intertriginous skin areas exhibits the histological hallmark of hidradenitis suppurativa (HS)/acne inversa, featuring a dissecting terminal hair folliculitis. Elevated serum levels of interleukin (IL)-17 and local increase in the ratio of proinflammatory T helper (Th)17 cells and anti-inflammatory regulatory T cells (Tregs) have been reported. Perifollicular Tregs play a key role in HF stem cell homeostasis and infundibular integrity.
OBJECTIVES
In this review, we evaluate the Th17/Treg ratio in HS, its aggravating conditions and associated comorbidities. Furthermore, we intended to clarify whether drugs with reported beneficial effects in the treatment of HS readjust the deviated Th17/Treg axis.
METHODS
PubMed-listed, peer-reviewed original research articles characterizing Th17/Treg regulation in HS/acne inversa and associated comorbidities were selected for this review.
RESULTS
This review presents HS as a disease that exhibits an increased Th17/Treg ratio. Perifollicular deficiencies in Treg numbers or function may disturb HF stem cell homeostasis, initiating infundibular dissection of terminal HFs and perifollicular inflammation. The Th17/Treg imbalance is aggravated by obesity, smoking and decreased Notch signalling. In addition, HS-associated autoimmune diseases exhibit a disturbed Th17/Treg axis resulting in a Th17-dominant state. All drugs that have beneficial effects in the treatment of HS normalize the Th17/Treg ratio.
CONCLUSIONS
HS immunopathogenesis is closely related to deviations of the Th17/Treg balance, which may negatively affect Treg-controlled HF stem cell homeostasis and infundibular integrity. Pharmacological intervention should not only attenuate Th17/IL-17 signalling, but should also improve Treg function in order to stabilize HF stem cell homeostasis and infundibular integrity.
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