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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Histological changes induced by JL-1 at both the light microscopic and t...
Histological changes induced by JL-1 at both the light microscopic and the electron microscopic levels. (A) Histological analysis of Silver-stained renal sections of mice injected with rabbit anti–mouse GBM and coinjected with either mAb JL-1 or IgG2b control mAb, obtained at 24 hours after injection. For JL-1–coinjected mice, images show pronounced inflammatory cell influx, focal capillary tuft occlusion by microthrombi, necrotizing lesions, nuclear debris, and wireloop-like lesions. Control-coinjected mice only display marginal inflammatory cell influx. Original magnification, ×400. (B) Quantification of histological changes using the activity index as described in Methods. (C) Electron microscopic analysis of glomerular lesions of mice injected with rabbit anti–mouse GBM and coinjected with either anti-C1q mAb JL-1 or control mAb IgG2b. At higher magnification, we observed several wireloop-like lesions in the JL-1–coinjected mice, whereas the IgG2b-coinjected mice did not display any abnormalities. Original magnifications, ×2,000 (left) and ×4,000 (right).