We report a novel pathomechanism for membranoproliferative glomerulonephritis type II (MPGN II) caused by a mutant Factor H protein expressed in the plasma. Genetic analyses of two patients revealed deletion of a single Lys residue (K224) located within the complement regulatory region in domain 4 of Factor H. This deletion resulted in defective complement control: mutant protein purified from the plasma of patients showed severely reduced cofactor and decay-accelerating activity, as well as reduced binding to the central complement component C3b. However, cell-binding activity of the mutant protein was normal and comparable to wild-type Factor H. The patients are daughters of consanguineous parents. As both patients but also their healthy mother were positive for C3 nephritic factor, the mutant Factor H protein is considered relevant for unrestricted activation of the disease-causing activation of the alternative complement pathway. Replacement of functional Factor H by fresh frozen plasma (10-15 ml/kg/14 days) was well tolerated, prevented so far disease progression in both patients, and is in the long run expected to preserve kidney function.

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To address the question of in situ production of IL-1 alpha and IL-1 beta in proliferative and non-proliferative forms of human glomerulonephritis (GN), we performed immunocytochemical and in situ hybridization studies on renal biopsies from patients with mesangial IgA-GN (N = 38), idiopathic membranous GN (MGN; N = 12), minimal change disease (MCD; N = 9), focal segmental glomerulosclerosis (FSGS; N = 5) and acute endocapillary GN (AGN; N = 3). Normal kidneys (N = 10) served as controls. Concomitantly, the expression of IL-1 receptor type I (IL-1 RI), IL-1 receptor type II (IL-1 RII) and of IL-1 receptor antagonist (IL-1 RA) was analyzed. Antibodies against antigens expressed on podocytes (PP-44), endothelial cells (CD31) and monocytes/macrophages (CD11b, CD14, CD68) were applied to attribute the expression of IL-1/IL-1 related peptides to intrinsic glomerular and/or blood-derived infiltrating cells. Our results demonstrate that IL-1 RII is constitutively expressed on endothelial cells, and its expression can be induced in proximal tubular cells and in the interstitium. In diseased glomeruli podocytes are capable of producing IL-1 alpha/beta. In MGN and MCD/FSGS, the expression of both IL-1 forms is particularly noted in early stages of the disease and is not only accompanied by a marked reactivity for IL-1 RI, but also for IL-1 RA. In segmental sclerosing lesions in FSGS and in IgA-GN with marked glomerular proliferation and/or sclerosis, a reduced expression of the PP-44 antigen and a diminished ability of podocytes to produce IL-1/IL-1 related peptides are noted. These results suggest that intrinsic glomerular production of IL-1 may be of relevance for the protection of glomeruli from continuing injury.

The renal outcome of shunt nephritis is good if early diagnosis and treatment is provided including i.v. antibiotics and total removal of the infected shunt. The possible progression to ESRD requires frequent nephrological monitoring of patients with ventriculoatrial shunts.

Retinoids are potent antiproliferative and anti-inflammatory compounds. We previously demonstrated that the natural pan-agonists all-trans retinoic acid (RA) and 13-cis RA efficiently preserve renal structure and function in rat mesangioproliferative glomerulonephritis. We examine effects of synthetic retinoid receptor-specific agonists 1) to identify common and receptor subtype-specific pathways in this model and 2) to characterize effects of retinoids on the renal endothelin (ET) system. Vehicle-injected control rats were compared with rats treated with daily subcutaneous injections of agonists specific for retinoid A (Ro-137410) and retinoid X (Ro-257386) receptors and the complex anti-activator protein-1 active retinoid BMS-453 7 days after induction of anti-Thy1.1 nephritis (n = 7-9/group). The different retinoids lowered glomerular ET-1 and ET type A and B receptor gene expression in control and nephritic rats with comparable efficacy. Reduction of glomerular c-Fos and GATA-2 mRNA expression levels suggests downregulation of transcription factors required for ET expression. The different retinoids were similar in their action on the glomerular capillary occlusion score, number of total glomerular cells, and glomerular infiltrating macrophage count. They differed in their ability to normalize blood pressure (Ro-257386 > BMS-453 > arotinoid), albuminuria (BMS-453 > Ro-257386 > arotinoid), and creatinine clearance (arotinoid > BMS-453 > Ro-257386). No signs of toxicity were observed. We conclude that all retinoid agonists with different subtype specificity are highly efficient in reducing renal damage and proliferation of mesangial cells. Retinoid X and A receptor-specific pathways are apparently involved in the antiproliferative, anti-inflammatory, and anti-ET action. Further studies are indicated to define the potential use of retinoid agonists in inflammatory renal disease.