Genetic Modulation of Anti-Myeloperoxidase Induced Murine Crescentic Glomerulonephritis
H Xiao, YW Zeng, F Pardo-Manuel De Villena, D Ciavatta, R Falk, JC Jenette. University of North Carolina, Chapel Hill, NC
Background: Anti-neutrophil cytoplasmic autoantibodies (ANCA), including anti-myeloperoxidase (MPO), are associated with crescentic glomerulonephritis (GN). Similar GN is induced in mice by injecting anti-MPO IgG. Patients have a spectrum of ANCA GN severity, whereas the inbred mouse strain that was initially used as a model (C57BL/6) has a narrow range of severity. The experiments reported here demonstrate that anti-MPO IgG causes GN of different severity in genetically different mice that is regulated primarily by differences in leukocyte responsivity to anti-MPO.
Design: Crescentic glomerulonephritis was induced in mice by iv injection of 50 μg/g anti-MPO IgG. Mice were sacrificed on day 6. Anti-MPO was given to: 1) 129S6 mice and C57BL/6 (B6) mice, 2) F1 mice from B6 x 129S6 mice, 3) F2 mice generated by B6 x 129S6 F1 intercross. 4) 129S1 mice, 5) chimeric mice with genetic differences between 129S6 or B6 donor bone marrow (BM) . To test the functional effects of genetically determined differences in disease severity, in vitro activation by anti-MPO IgG was evaluated in neutrophils from B6, 129S6 and 129S mice. Neutrophils were primed with 10ng/ml TNFa, stimulated with anti-MPO IgG, and superoxide generation measured.
Results: After injection of anti-MPO IgG: 1) B6 mice (n=17) developed an average 9% crescents, whereas 129S6 mice (n=13) developed 69% crescents. 2) F1 (B6 x 129S6) mice developed 13.5% crescents. 3) Of 60 F2 mice, 30 had < 10%, 24 10-25 %, 5 26-50% and 1 >50% crescents. 4) 129S1 developed 21% crescents and thus had less disease than 129S6 mice. 5) Rag2-/- B6 mice (n=4) that received BM from 129S6 mice had 79% crescents similar to 129S6 mice; however, Rag2-/-129S6 mice (n=6) that received BM from B6 mice had 17% crescents more similar to B6 mice. In the functional assays, anti-MPO IgG caused more activation of neutrophils from 129S6 mice than neutrophils from B6 or 129S1 mice.
Conclusions: 1) pathogenic events in this model of ANCA disease are influenced by genetic factors, 2) this genetic influence acts primarily through modulation of the responsivity of bone marrow derived cells (e.g. neutrophils) to activation by ANCA, 3) identification of the genes responsible for this modulation should reveal genes and gene products that have important roles in pathogenesis of ANCA disease, and could be markers of disease activity and outcome, as well as targets for therapy.
Category: Kidney (does not include tumors)
Monday, March 22, 2010 1:15 PM
Platform Session: Section H, Monday Afternoon