Digital immunohistological dissection of immune privilege collapse in syringotropic autoimmune diseases: Implication for the pathogenesis

Abstract

Background: Syringotropic cell infiltration is a histological hallmark of some autoimmune diseases. However, its underlying mechanism remains unclear.

Objectives: To assess the immune privilege (IP) of the human sweat gland (SwG) in homeostasis and in syringotropic autoimmune diseases.

Methods: We combined quantitative digital image microdissection with immunohistochemisty to analyze IP molecule expression in SwG of normal and diseased skin. The human skin organ culture model was used to examine the influence of proinflammatory conditions on IP in SwG.

Results: In the normal subjects (n = 10), major histocompatibility complex (MHC) class І expression was significantly reduced in SwGs compared to the epidermis. In contrast, IP-guardians, macrophage migration inhibitory factor (MIF) and alpha-melanocyte stimulating hormone (α-MSH) were upregulated in SwGs. MHC class І was upregulated in whole SwGs in lupus erythematosus (LE; n = 7) and scleroderma/morphea (Scl; n = 9), whereas differential expression was noted only in the secretory portion in Sjögren's syndrome (SjS) (n = 4). MIF expression level inversely correlated with that of MHC class I in all samples tested, and downregulation of α-MSH was detected in LE SwGs alone. The severity of inflammatory changes and MIF and ⍺-MSH expression were inversely correlated in LE. CD200 expression was decreased exclusively in atrophic stage of Scl. In a human skin organ culture model, intratissue injection of interferon-gamma up-regulated MHC class I and downregulated MIF and α-MSH.

Conclusions: These findings indicate that SwGs enjoy IP. Dysregulated IP molecule expression may lead to SwG IP collapse and contribute to distinct inflammatory cell distribution in syringotropic autoimmune disorders.

Keywords: autoimmune diseases; digital image analysis; immune privilege; sweat gland; syringotropism.