Possible implication of intermolecular epitope spreading in the production of anti-glomerular basement membrane antibody in anti-neutrophil cytoplasmic antibody-associated vasculitis

Abstract

ObjectiveAnti-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. Methods 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. Results 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. ConclusionThe 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.

Double-Positive Anti–Glomerular Basement Membrane Antibody and Myeloperoxidase Antineutrophil Cytoplasmic Autoantibody–Associated Glomerulonephritis Post COVID-19 mRNA vaccine: A Case Series of 4 Patients

“…One recent study suggests that proteases released by neutrophils activated by ANCA digest collagen type IV to expose GBM epitopes. 25 Following this, CD11c+ macrophages specific to ANCA-associated vasculitis are responsible for antigen presentation of the GBM epitopes to T cells, resulting in the production of anti-GBM antibodies. Moreover, in an in vitro study using human cells, Kubala et al 26 demonstrated that MPO binds to collagen IV in the extracellular matrix in a dose-dependent fashion.…”

Clinicopathological characterization of subgroups in anti-glomerular basement membrane nephritis patients From a Single Center in China: A 12-Year observational study

“…5 cases showed granular deposition of IgG1 along the mesangial area and capillary wall, and the other case was negative. The latest study showed that the release of ANCA can damage the kidney and then result in the revelation of a3(IV)NC1, leading to in ltration of CD11c + macrophages, subsequently the exposed GBM epitope can induce the formation of anti-GBM antibodies [12] . Furthermore, there are data showing that the target antigen of anti-GBM in anti-GBM positive patients is the NC1 region of the α3 chain of type IV collagen, irrespective of whether they are combined with ANCA or not [13] .…”

Goodpasture syndrome and anti-glomerular basement membrane disease

“…The pathogenic mechanism of this association is still debated, but since low levels of ANCA may be detected years before the appearance of anti-GBM antibodies and clinical symptoms, it has been hypothesised that ANCA antibodies may induce glomerular inflammation that modify or expose usually sequestered disease epitopes in GBM, triggering anti-GBM antibodies formation (28). A recent study by Nishibata demonstrated that proteases released from neutrophils activated by ANCA can digest type IV collagen with subsequent unveiling of alpha-3(IV) NC (60). Another study demonstrated that up to 60% anti-GBM patients also have autoantibodies that target linear epitopes of MPO, versus 24% with autoantibodies that target intact MPO.…”