Mesangial Cell-Binding Anti-DNA Antibodies in Patients with Systemic Lupus Erythematosus

Abstract

ABSTRACT. The mechanisms by which anti-DNA antibodies contribute to the pathogenesis of lupus nephritis (LN) remain to be elucidated. This study investigates the binding of polyclonal anti-DNA immunoglobulins from patients with systemic lupus erythematosus (SLE) to human mesangial cells (HMC) in vitro. Testing of cross-sectional serum samples from 280 LN patients (108 during active disease; 172 during remission), 35 SLE patients without renal involvement, 72 patients with non-lupus primary glomerular diseases, and 37 healthy subjects with a cellular enzyme-linked immunosorbent assay showed significant IgG mesangial cell-binding activity in patients with SLE, particularly those with active LN (P < 0.0001). Significant HMC-binding activity was demonstrated in 83.9%, 42.8%, and 47.1% of patients with active LN, inactive LN, and non-renal SLE, respectively. This was predominantly attributed to binding by anti-DNA antibodies, and immune complex binding accounted for 4.6%, 3.5%, and 2.8% of seropositive samples in the respective groups. Longitudinal studies in 27 LN patients demonstrated correlation between serial levels of anti-DNA antibodies, serum HMC-binding activity, and disease activity in 18 patients (66.7%). Affinity-purified polyclonal IgG anti-DNA antibodies from sera with HMC-binding activity showed significant binding to cultured HMC, and to a lesser extent glomerular and proximal tubular epithelial cells and human umbilical vein endothelial cells, but not tumor cell lines, peritoneal mesothelial cells, bronchial epithelial cells, or fibroblasts. The binding of anti-DNA antibodies to HMC was increased 1.47-fold (P = 0.0059) after the removal of Ig-associated DNA by DNase treatment, but it was unaffected by DNase treatment of HMC membrane. Controlled trypsinization of membrane proteins in HMC resulted in a 1.26-fold (P = 0.0025) increase in their binding by anti-DNA antibodies. In conclusion, subsets of anti-DNA antibodies from patients with SLE are capable of binding to HMC. The association of such binding with renal involvement and disease activity and its modulation by DNA concentration suggest that Ig binding to HMC can be a potential marker for disease activity in selected patients and that the binding of anti-DNA antibodies to HMC may be a pathogenetic mechanism in LN.

Role of TLR9 in Anti-Nucleosome and Anti-DNA Antibody Production in lpr Mutation-Induced Murine Lupus

“…The authors suggest that other specificities, anti-Sm for example, may play a pathogenic role in their models. In our study, the persistence and even the increased production of anti-dsDNA Abs could explain the elevated mesangial proliferation in TLR9-deficient mice since it has been clearly demonstrated that the level of anti-DNA Abs is associated with the importance of nephritis (21,22). Our data, as do the other recent reports concerning TLR9-deficient lupus mice (23), provide clear evidence for a protective role of TLR9 in the development of the lupus disease since all TLR9 Ϫ/Ϫ lupus mice present more intense renal deposits, proteinuria, and lymphadenopathy than their normal counterparts.…”

“…glomerular IgG deposits and mesangial glomerulonephritis can occur in TLR9-deficient mice in the absence of anti-nucleosome Abs (21,22). …”

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo

“…Anti-dsDNA antibodies were isolated from both serum and renal biopsies of several LN patients. 32 On repeated experiments, purified antidsDNA recognized several histones (only H1 and H2b were negative) but did not recognize a-enolase, even when the amount of the protein in the dot blot assay was significantly increased (Figure 6, D-F). At variance, in the same dot blot essay using the same a-enolase amount, anti-a-enolase antibodies recognized the protein at low concentration (5 mg).…”

Anti‐DNA antibody induction of protein kinase C phosphorylation and fibronectin synthesis in human and murine lupus and the effect of mycophenolic acid

“…Anti-DNA antibodies have been implicated in the pathogenesis of disease and can be eluted from renal and glomerular specimens from humans and mice with lupus nephritis (3,4). In addition, anti-DNA antibody titers correlate with disease activity, and glomerulonephritis can be induced in nonautoimmune mice upon inoculation with the transgene encoding an IgG anti-DNA antibody (5,6).…”

“…We have previously demonstrated that polyclonal anti-DNA antibodies isolated from patients with active lupus nephritis could bind to the surface of human mesangial cells and induce the synthesis of cytokines and components of the extracellular matrix (5,19). We therefore investigated the effects of MPA on proinflammatory and profibrotic processes in human mesangial cells upon stimulation with anti-DNA antibodies.…”