1. ¹Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
2. ²Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
3. ³Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
4. ⁴Department of Internal Medicine, Division of Nephrology and Department of Otolaryngology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA

Correspondence: Sanjeev Sethi, Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA. E-mail: sethi.sanjeev@mayo.edu

Received 21 July 2008; Revised 30 September 2008; Accepted 4 November 2008; Published online 28 January 2009.

Abstract

Dense Deposit Disease (DDD), or membranoproliferative glomerulonephritis type II, is a rare renal disease characterized by dense deposits in the mesangium and along the glomerular basement membranes that can be seen by electron microscopy. Although these deposits contain complement factor C3, as determined by immunofluorescence microscopy, their precise composition remains unknown. To address this question, we used mass spectrometry to identify the proteins in laser microdissected glomeruli isolated from paraffin-embedded tissue of eight confirmed cases of DDD. Compared to glomeruli from five control patients, we found that all of the glomeruli from patients with DDD contain components of the alternative pathway and terminal complement complex. Factor C9 was uniformly present as well as the two fluid-phase regulators of terminal complement complex clusterin and vitronectin. In contrast, in nine patients with immune complex–mediated membranoproliferative glomerulonephritis, glomerular samples contained mainly immunoglobulins and complement factors C3 and C4. Our study shows that in addition to fluid-phase dysregulation of the alternative pathway, soluble components of the terminal complement complex contribute to glomerular lesions found in DDD.