The aim of the present study was to investigate the events following interaction of antibody with an antigen planted on the surface of glomerular endothelial cell (GEN). A lectin, Helix pomatia agglutinin (HPA), was planted at the surface of rat GEN by the perfusion of the isolated left kidney with neuraminidase (NRD) and HPA. A subsequent perfusion with IgG fraction, but not with Fab fragments, of rabbit anti-HPA serum induced formation of granular immune deposits (IDs) on the surface of GEN. When the left kidney was revascularized after initial formation of IDs, acute glomerulonephritis ensued. Fifteen minutes after revascularization, granular IDs were observed at the subendothelial space. Two days later, there was decrease of subendothelial IDs with concomitant appearance of subepithelial IDs. At the seventh day, IDs were mainly localized in the subepithelial space. The results suggest that this model of experimental glomerulonephritis is characterized by: (1) initial formation of HPA immune complexes (ICs) at the surface of GEN; and by (2) subsequent movement of ICs from luminal side to subepithelial area with local formation of IDs. The results are relevant to the understanding of the kinetics of ICs resulting from interaction of antibodies with exogenous antigens "planted" in the glomerular capillary walls, and of the local formation of IDs.
BackgroundGlomerular Immune complex (IC) deposition causes glomerulonephritis in lupus nephritis. The reaction of intrinsic glomerular cells differs according to the area of IC deposition. Subepithelial IC deposits cause functional and structural changes on podocytes (glomerular visceral epithelial cells) through complement pathway activation as is well known in membranous glomerulonephritis. In this setting, podocytes can induce some complement factors including complement factor H (CFH) which serves not only to regulate the alternative pathway but also to process subepithelial IC deposition.1 However, whether podocyte processing of IC deposition is limited to only the subendothelial area is obscure.ObjectivesTo clarify the role of podocytes in IC deposition in the glomerular subendothelial area.MethodsNEP25 mice genetically expressing human CD25 in podocytes were used. Intravenous immunotoxin for human CD25 (LMB2) provokes podocyte-specific injury (NEP25/LMB2). By shortening the period of LMB2 exposure to NEP25 mice, we mitigated the podocyte injury. We administered intraperitoneally IgG3-producing hybridoma clones, 2B11.3, which were previously established from an unmanipulated MRL/lpr mouse, to NEP25 mice (NEP25/hybridoma). Furthermore, we also injected short-term LMB2 to NEP25/hybridoma mice (NEP25/hybridoma/LMB2). We investigated IC deposits by immunofluorescence and electronic microscopic study. We measured complement regulatory factor mRNA expression including CFH, complement factor I (CFI), decay-accelerating factor (DAF), complement receptor 1-related gene/protein y (Crry), C3a receptor (C3aR) and C5a receptor (C5aR) of isolated glomeruli of each mouse by quantitative real time-PCR. In an in vitro study, we assessed CFH mRNA expression of immortalised mouse podocytes injured by puromycin.ResultsFirst, NEP25/LMB2 mice showed glomerular tuft collapse with epithelial cell hyperplasia, suggesting podocyte loss by light microscopy study as reported previously. mRNA expression of all complement regulatory factors but C5aR was decreased in NEP25/LMB2 mice as compared with NEP25 mice. This result suggests that podocytes produce these complement regulatory factors. On the other hand, when the podocyte injury was mitigated, CFH and C3aR mRNA expression increased, and CFI, DAF and Crry mRNA expression decreased as compared with NEP25 mice. Second, we detected IC deposition only in the glomerular subendothelial area without endocapillary proliferative lesion in NEP25/hybridoma mice. They showed increase of C3aR mRNA expression, and decrease of CFI and DAF mRNA expression as compared with controls. Notably, subendothelial IC deposition did not alter CFH mRNA expression. Third, NEP25/hybridoma/LMB2 (milder podocyte injury) showed decrease of IC deposits in glomeruli and increase of only CFH mRNA expression (1.7-fold) as compared to NEP25/hybridoma mice, while there was no significant change in mRNA expression of other complement regulatory factors. Finally, puromycin-induced mild podocyte injury promoted CFH mRNA expr...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.