Adriamycin nephropathy is a model of focal segmental glomerulosclerosis, characterized by proteinuria and progressive glomerulosclerosis and tubulointerstitial damage. In this study, we examined the role of complement in the etiology of adriamycin nephropathy in mice. We used mice deficient in C1q, factor D, C3, and CD59, and compared them with strain-matched controls. C3 deposition occurred in the glomeruli of wild-type mice as early as 48 h following a single i.v. injection of adriamycin. C3-deficient mice developed significantly less proteinuria and less podocyte injury at day 3 postadriamycin than controls, suggesting that complement is important in mediating the early podocyte injury. At later time points, C3-deficient mice were protected from glomerulosclerosis, tubulointerstitial injury, and renal dysfunction. Factor D-deficient mice were also protected from renal disease, confirming the importance of alternative pathway activation in this model. In contrast, C1q-deficient mice developed similar disease to controls, indicating that the complement cascade was not activated via the classical pathway. CD59-deficient mice, which lack adequate control of C5b-9 formation, developed significantly worse histological and functional markers of renal disease than controls. Interestingly, although more C9 deposited in glomeruli of CD59-deficient mice than controls, in neither group was tubulointerstitial C9 staining apparent. We have demonstrated for the first time that alternative pathway activation of complement plays an important role in mediating the initial glomerular damage in this in vivo model of focal segmental glomerulosclerosis. Lack of CD59, which regulates the membrane attack complex, led to greater glomerular and tubulointerstitial injury.

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Many forms of glomerulonephritis are triggered by Ab localization in the glomerulus, but the mechanisms by which this induces glomerular inflammation are not fully understood. In this study we investigated the role of complement in a mouse model of cryoglobulin-induced immune complex glomerulonephritis. Several complement-deficient mice on a C57BL/6 and BALB/c genetic background were used and compared with strain-matched, wild-type controls. Cryoglobulinemia was induced by i.p. injection of 6-19 hybridoma cells producing an IgG3 cryoglobulin with rheumatoid factor activity against IgG2a of allotype a present in BALB/c, but not C57BL/6, mice. Thus, the cryoprecipitate in C57BL/6 mice consisted of the IgG3 cryoglobulin only (type I cryoglobulinemia) compared with IgG3-IgG2a complexes in BALB/c (type II cryoglobulinemia). The survival of mice was not affected by complement deficiency. Glomerular influx of neutrophils was significantly less in C3-, factor B-, and C5-deficient mice compared with wild-type and C1q-deficient mice. It did not correlate with C3 deposition, but did correlate with the amount of C6 deposited. Deficiency of CD59a, the membrane inhibitor of the membrane attack complex, did not induce an increase in neutrophil infiltration, suggesting that the generation of C5a accounts for the effects observed. There was no apparent difference between cryoglobulinemia types I and II regarding the role of complement. Our results suggest that in this model of cryoglobulin-induced glomerulonephritis the neutrophil influx was mediated by C5 activation with the alternative pathway playing a prominent role in its cleavage. Thus, blocking C5 is a potential therapeutic strategy for preventing renal injury in cryoglobulinemia.

Advances in our understanding of the role of complement in glomerular injury point to the likely therapeutic benefits of targeting the complement system. Many new drugs are becoming available. Careful dissection of the pro and antiinflammatory effects of the complement system which the experimental models allow will assist in designing directed therapy that will avoid the detrimental effects of nonspecific systemic complement inhibition.

The terminal complement components C5a and the membrane attack complex are involved in the pathogenesis of ischemia-reperfusion injury in many organs. CD59 is the major regulator of membrane attack complex formation. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in renal ischemia-reperfusion injury. Unilateral ischemia-reperfusion injury was induced by clamping the left renal pedicle for 30 minutes under general anesthetic. Mice were studied at 72 hours and 2 weeks after ischemia-reperfusion injury. mCd59a-/- mice developed significantly greater tubular injury (P = 0.01), tubulointerstitial apoptosis (P = 0.02), and neutrophil influx (P = 0.04) than controls at 72 hours after ischemia-reperfusion. Two weeks after ischemia-reperfusion, mCd59a-/- mice exhibited more severe tubular damage predominantly in a corticomedullary distribution than controls (P = 0.02). Quantification of interstitial leukocytes revealed significantly greater numbers of infiltrating lymphocytes (but not macrophages) in mCd59a-/- mice than controls (P = 0.04) at 2 weeks. At both time points, significantly more C9 (as a marker of membrane attack complex) deposition occurred in a peritubular distribution in mCd59a-/- mice than controls. In conclusion, these results demonstrate that the lack of CD59a, by allowing unregulated membrane attack complex deposition, exacerbates both the tubular injury and the interstitial leukocyte infiltrate after ischemia-reperfusion injury in mice.