Effects of complement factor D deficiency on the renal disease of MRL/lpr mice.
BACKGROUND
The alternative complement pathway (AP) is activated in individuals with lupus nephritis and in murine models of systemic lupus erythematosus, including MRL/lpr mice. A previous study from our laboratory evaluated the development of renal disease in MRL/lpr mice genetically deficient in factor B (Bf-/-), a protein necessary for AP activation. MRL/lpr Bf-/- mice developed less renal disease and had improved survival; however, these mice were also a different major histocompatibility complex (MHC) haplotype (H-2b) than their wild-type littermates (H-2k) due to the gene for Bf being located in the MHC gene complex. We undertook the current study to determine if the decreased renal disease in MRL/lpr Bf-/- mice was due to the lack of AP activation or the H-2b haplotype by studying the effects of factor D (Df) deficiency, a critical protein for AP activation, on disease development in MRL/lpr mice.


METHODS
Df-deficient mice were backcrossed with MRL/lpr mice for four to nine generations. MRL/lpr H-2k Df-/-, Df+/-, and Df+/+ littermates were evaluated for disease development. Lack of AP activation in MRL/lpr Df-/- mice was determined by the zymosan assay. Serum creatinine levels were measured using a creatinine kit. Proteinuria and autoantibody levels were determined by enzyme-linked immunosorbent assay (ELISA). Sections from one kidney were stained with fluorescein isothiocyanate (FITC) alpha-murine C3 or alpha-murine IgG to detect C3 and IgG deposition. The remaining kidney was cut in half with one half fixed, sectioned, and stained with hematoxylin and eosin and periodic acid-Schiff (PAS) to evaluate pathology and another half fixed in glutaraldehyde and examined via electron microscopy.


RESULTS
MRL/lpr Df-/- mice had similar glomerular IgG deposition, proteinuria and autoantibody levels, as Df+/+ and Df+/- littermates. However, glomerular C3 deposition, serum creatinine levels, and pathologic renal disease were significantly reduced in Df-/- mice. Despite the lack of renal disease in Df-/- mice, life span was not impacted by factor D deficiency.


CONCLUSIONS
The absence of Df and AP activation is protective against the development of proliferative renal disease in MRL/lpr mice suggesting the similar effect of Bf deficiency in MRL/lpr mice was also due to the lack of AP activation.
Elliott
Margaret K
MK
Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA.
Jarmi
Tambi
T
Ruiz
Phil
P
Xu
Yuanyuan
Y
Holers
V Michael
VM
Gilkeson
Gary S
GS
D000818:Animals; D001323:Autoantibodies / Q000097:blood; D003176:Complement C3 / Q000378:metabolism; D011416:Complement Factor D / Q000172:deficiency / Q000235:genetics*; D003170:Complement Pathway, Alternative / Q000502:physiology*; D003404:Creatinine / Q000097:blood; D005260:Female; D015432:Glomerulonephritis, Membranoproliferative / Q000276:immunology / Q000401:mortality / Q000473:pathology / Q000503:physiopathology; D007074:Immunoglobulin G / Q000378:metabolism; D007678:Kidney Glomerulus / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008181:Lupus Nephritis / Q000276:immunology / Q000401:mortality / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D051379:Mice; D019463:Mice, Inbred MRL lpr; D008854:Microscopy, Electron; D011507:Proteinuria / Q000276:immunology / Q000401:mortality / Q000473:pathology / Q000503:physiopathology; D015996:Survival Rate
D001323:Autoantibodies; D003176:Complement C3; D007074:Immunoglobulin G; D003404:Creatinine; D011416:Complement Factor D; C493491:complement factor D, mouse