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Profiling the human hair follicle immune system in lichen planopilaris and frontal fibrosing alopecia: can macrophage polarization differentiate these two conditions microscopically?
Author(s) -
Harries M.,
Hardman J.,
Chaudhry I.,
Poblet E.,
Paus R.
Publication year - 2020
Publication title -
british journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.304
H-Index - 179
eISSN - 1365-2133
pISSN - 0007-0963
DOI - 10.1111/bjd.18854
Subject(s) - hair follicle , scarring alopecia , pathology , biology , cd68 , immunology , medicine , immunohistochemistry , endocrinology , anatomy , scalp
Summary Background Frontal fibrosing alopecia ( FFA ) is traditionally regarded as a variant of lichen planopilaris ( LPP ) based on histological features. Distinct clinical presentation, demographics and epidemiology suggest that differing pathogenic factors determine the final phenotype. Objectives To map the hair follicle immune system in LPP and FFA by systematically comparing key inflammatory markers in defined hair follicle compartments. Methods Lesional scalp biopsies from LPP and FFA and healthy controls were stained with the following immunohistochemical markers: CD 1a and CD 209, CD 4, CD 8, CD 56, CD 68, CD 123, CXCR 3, forkhead box ( FOX )P3, mast cell tryptase and cK it. Macrophage polarization was explored using CD 206, CD 163, CD 86, receptor for advanced glycation end products ( RAGE ), interleukin ( IL )‐4 and IL ‐13 on paired lesional and nonlesional LPP and FFA samples. Results Increased numbers of CD 8 + , CXCR 3 + and FOXP 3 + T cells and CD 68 + macrophages were identified in the distal hair follicle epithelium and perifollicular mesenchyme in both LPP and FFA compared with controls. In both LPP and FFA , total and degranulated mast cells and CD 123 + plasmacytoid dendritic cells were increased in the perifollicular mesenchyme adjacent to the bulge and infundibulum, whereas numbers of CD 1a + and CD 209 + dendritic cells were significantly reduced in the infundibulum connective tissue sheath. However, only with CD 68 staining was a significant difference between LPP and FFA identified, with greater numbers of CD 68 + cells in LPP samples. Furthermore, the identified macrophage polarization markers downregulated CD 86 and upregulated CD 163 and IL ‐4 expression in lesional LPP compared with FFA samples. Conclusions This comparative immunopathological analysis is the first to profile systematically the hair follicle immune system in LPP and FFA . Our analysis highlights a potential role of macrophages in disease pathobiology and suggests that macrophage polarization may differ between LPP and FFA , allowing microscopic differentiation. Linked Comment: Kinoshita‐Ise. Br J Dermatol 2020; 183 :419–420.