Anti-C1q autoantibodies deposit in glomeruli but are only pathogenic in combination with glomerular C1q-containing immune complexes
Leendert A. Trouw, Tom W.L. Groeneveld, Marc A. Seelen, Jacques M.G.J. Duijs, Ingeborg M. Bajema, Frans A. Prins, Uday Kishore, David J. Salant, J. Sjef Verbeek, Cees van Kooten, Mohamed R. Daha
Leendert A. Trouw, Tom W.L. Groeneveld, Marc A. Seelen, Jacques M.G.J. Duijs, Ingeborg M. Bajema, Frans A. Prins, Uday Kishore, David J. Salant, J. Sjef Verbeek, Cees van Kooten, Mohamed R. Daha
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Article Autoimmunity

Anti-C1q autoantibodies deposit in glomeruli but are only pathogenic in combination with glomerular C1q-containing immune complexes

Abstract

Anti-C1q autoantibodies are present in sera of patients with several autoimmune diseases, including systemic lupus erythematosus (SLE). Strikingly, in SLE the presence of anti-C1q is associated with the occurrence of nephritis. We have generated mouse anti–mouse C1q mAb’s and used murine models to investigate whether anti-C1q autoantibodies actually contribute to renal pathology in glomerular immune complex disease. Administration of anti-C1q mAb JL-1, which recognizes the collagen-like region of C1q, resulted in glomerular deposition of C1q and anti-C1q autoantibodies and mild granulocyte influx, but no overt renal damage. However, combination of JL-1 with a subnephritogenic dose of C1q-fixing anti–glomerular basement membrane (anti-GBM) antibodies enhanced renal damage characterized by persistently increased levels of infiltrating granulocytes, major histological changes, and increased albuminuria. This was not observed when a non–C1q-fixing anti-GBM preparation was used. Experiments with different knockout mice showed that renal damage was dependent not only on glomerular C1q and complement activation but also on Fcγ receptors. In conclusion, anti-C1q autoantibodies deposit in glomeruli together with C1q but induce overt renal disease only in the context of glomerular immune complex disease. This provides an explanation why anti-C1q antibodies are especially pathogenic in patients with SLE.

Authors

Leendert A. Trouw, Tom W.L. Groeneveld, Marc A. Seelen, Jacques M.G.J. Duijs, Ingeborg M. Bajema, Frans A. Prins, Uday Kishore, David J. Salant, J. Sjef Verbeek, Cees van Kooten, Mohamed R. Daha

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Anti-C1q autoantibodies react with C1q in the glomerulus in a planted an...
Anti-C1q autoantibodies react with C1q in the glomerulus in a planted antigen–like fashion. (A) C1q sandwich ELISA for serum levels of C1q in naive WT mice, WT mice treated with JL-1, naive Rag2–/– mice, and Rag2–/– mice pretreated with PBS or with mouse IgG and then treated with JL-1. (B) Immunofluorescence analysis of renal sections of Rag2–/– mice, either naive or reconstituted for mouse IgG followed by injection of either JL-1 or PBS. Images show the absence of IgG and C1q in naive Rag2–/– mice and positivity for IgG and C1q, both mesangially and along the GBM, in IgG-reconstituted mice. The positivity for IgG and C1q is highly increased following administration of JL-1. Original magnification, ×400. (C) Quantification of immunofluorescence analysis of the glomerular deposition of IgG and C1q.