Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Japan.
Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Clin Exp Rheumatol. 2022 May;40(4):691-704. doi: 10.55563/clinexprheumatol/6oq9du. Epub 2022 Feb 4.
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is sometimes complicated by anti-glomerular basement membrane (GBM) disease. Proteases, including elastase, released from neutrophils activated by ANCA are implicated in the pathogenesis of AAV. Epitopes of anti-GBM antibody exist in the α3-subunit non-collagenous (NC1) domain of collagen type IV [Col (IV)]. This region, called α3(IV)NC1, is structurally cryptic. This study aimed to determine the production mechanism of anti-GBM antibody in AAV.
We first examined whether α3(IV)NC1 could be revealed by the digestion of formalin-fixed, paraffin-embedded (FFPE) normal kidney sections and Col (IV) by proteases, including neutrophil elastase, using immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Next, the reveal of α3(IV)NC1 and the infiltration of CD11c+ macrophages in the affected kidneys were evaluated by IHC and immunofluorescent staining using FFPE sections. Finally, the production of anti-GBM antibody in AAV rats was determined by ELISA.
α3(IV)NC1 was revealed by the digestion of FFPE normal kidney sections and Col (IV) by proteases. Although the reveal of α3(IV)NC1 was observed in sclerotic glomeruli regardless of causative diseases, CD11c+ macrophages near α3(IV)NC1 were characteristics of AAV. Anti-GBM antibody was produced subsequent to ANCA in some AAV rats. IHC demonstrated the reveal of α3(IV)NC1 in affected renal tissues and the infiltration of CD11c+ macrophages around the sites.
The collective findings suggest that, in AAV, proteases released from neutrophils activated by ANCA digest Col (IV) and result in the reveal of α3(IV)NC1, CD11c+ macrophages present GBM epitopes, and then the host's immune system produce anti-GBM antibody.
抗中性粒细胞胞浆抗体（ANCA）相关性血管炎（AAV）有时会并发抗肾小球基底膜（GBM）病。由 ANCA 激活的中性粒细胞释放的蛋白酶，如弹性蛋白酶，被认为与 AAV 的发病机制有关。抗 GBM 抗体的表位存在于 IV 型胶原的α3 亚单位非胶原（NC1）结构域[Col (IV)]中。该区域称为α3(IV)NC1，结构上是隐匿的。本研究旨在确定 AAV 中抗 GBM 抗体的产生机制。
我们首先通过免疫组织化学（IHC）和酶联免疫吸附测定（ELISA），检查蛋白酶（包括中性粒细胞弹性蛋白酶）能否消化福尔马林固定、石蜡包埋（FFPE）的正常肾脏切片和 Col (IV)，从而揭示α3(IV)NC1。接下来，我们通过 IHC 和免疫荧光染色，评估 FFPE 切片中受影响肾脏中α3(IV)NC1 的揭示和 CD11c+巨噬细胞的浸润情况。最后，通过 ELISA 测定 AAV 大鼠中抗 GBM 抗体的产生情况。
蛋白酶可消化 FFPE 正常肾脏切片和 Col (IV)，从而揭示α3(IV)NC1。尽管无论病因如何，硬化性肾小球中都可以观察到α3(IV)NC1 的揭示，但 CD11c+巨噬细胞靠近α3(IV)NC1 是 AAV 的特征。在一些 AAV 大鼠中，继 ANCA 之后产生了抗 GBM 抗体。免疫组化显示，受影响的肾组织中揭示了α3(IV)NC1，并且在这些部位周围浸润了 CD11c+巨噬细胞。
这些结果表明，在 AAV 中，由 ANCA 激活的中性粒细胞释放的蛋白酶消化 Col (IV)，导致α3(IV)NC1 的揭示，CD11c+巨噬细胞呈现 GBM 表位，然后宿主的免疫系统产生抗 GBM 抗体。
