Administration of a soluble recombinant complement C3 inhibitor protects against renal disease in MRL/lpr mice

Complement-dependent apoptosis and inflammatory gene changes in murine lupus cerebritis

The role of complement activation in the brains of MRL/lpr lupus mice was determined using the potent C3 convertase inhibitor, CR1-related y (Crry), administered both as an overexpressing Crry transgene and as Crry-Ig. Prominent deposition of complement proteins C3 and C9 in brains of MRL/lpr mice was indicative of complement activation and was significantly reduced by Crry. Apoptosis was determined in brain using different independent measures of apoptosis, including TUNEL staining, DNA laddering, and caspase-3 activity, all of which were markedly increased in lupus mice and could be blocked by inhibiting complement with Crry. Complement activation releases inflammatory mediators that can induce apoptosis. The mRNA for potentially proinflammatory proteins such as TNFR1, inducible NO synthase, and ICAM-1 were up-regulated in brains of lupus mice. Crry prevented the increased expression of these inflammatory molecules, indicating that the changes were complement dependent. Furthermore, microarray analysis revealed complement-dependent up-regulation of glutamate receptor (AMPA-GluR) expression in lupus brains, which was also validated for AMPA-GluR1 mRNA and protein. Our results clearly demonstrate that apoptosis is a prominent feature in lupus brains. Complement activation products either directly and/or indirectly through TNFR1, ICAM-1, inducible NO synthase, and AMPA-GluR, all of which were altered in MRL/lpr mouse brains, have the potential to induce such apoptosis. These findings present the exciting possibility that complement inhibition is a therapeutic option for lupus cerebritis.

Local extravascular pool of C3 is a determinant of postischemic acute renal failure

The third complement component (C3) is an acute phase protein that plays a central role in reperfusion injury in several organ models. To investigate the contribution of local synthesis of C3 and distinguish it from that of circulating complement mainly produced by hepatic synthesis, we employed a mouse renal isograft model. Our model demonstrated a close relationship between the extent of intrarenal expression of C3 and cold-ischemia induced injury. Ischemic C3-positive donor kidneys transplanted into C3-positive or C3-negative recipients developed widespread tissue damage and severe acute renal failure. In contrast, ischemic C3-negative isografts exhibited only mild degrees of functional and structural disturbance, even when transplanted into normal C3-positive recipients. Thus local synthesis of C3, mostly identified in the tubular epithelium, was essential for complement-mediated reperfusion damage, whereas circulating C3 had a negligible effect. Our results suggest a two-compartment model for the pathogenic function of C3, in which the extravascular compartment is the domain of local synthesis of C3, and where the role of circulating C3 is redundant. Our data cast new light on the mechanism of complement-mediated tissue injury in nonimmunological disorders, and challenges the longstanding dogma that circulating components are the main complement effectors of extravascular tissue damage.

Strategies of therapeutic complement inhibition

The involvement of complement in the pathogenesis of a great number of partly life threatening diseases defines the importance to develop inhibitors which specifically interfere with its deleterious action. Endogenous soluble complement-inhibitors, antibodies or low molecular weight antagonists, either blocking key proteins of the cascade reaction or neutralizing the action of the complement-derived anaphylatoxins have successfully been tested in various animal models over the past years. Promising results consequently led to first clinical trials. This review is focused on different approaches for the development of inhibitors, on their site of action in the cascade, on possible indications for complement inhibition based on experimental animal data, and on potential side effects of such treatment.

Mechanisms of immune-deposit formation and the mediation of immune renal injury

The passive trapping of preformed immune complexes is responsible for some forms of glomerulonephritis that are associated with mesangial or subendothelial deposits. The biochemical characteristics of circulating antigens play important roles in determining the biologic activity of immune complexes in these cases. Examples of circulating immune complex diseases include the classic acute and chronic serum sickness models in rabbits, and human lupus nephritis. Immune deposits also form "in situ". In situ immune deposit formation may occur at subepithelial, subendothelial, and mesangial sites. In situ immune-complex formation has been most frequently studied in the Heymann nephritis models of membranous nephropathy with subepithelial immune deposits. While the autoantigenic target in Heymann nephritis has been identified as megalin, the pathogenic antigenic target in human membranous nephropathy had been unknown until the recent identification of neutral endopeptidase as one target. It is likely that there is no universal antigen in human membranous nephropathy. Immune complexes can damage glomerular structures by attracting circulating inflammatory cells or activating resident glomerular cells to release vasoactive substances, cytokines, and activators of coagulation. However, the principal mediator of immune complex-mediated glomerular injury is the complement system, especially C5b-9 membrane attack complex formation. C5b-9 inserts in sublytic quantities into the membranes of glomerular cells, where it produces cell activation, converting normal cells into resident inflammatory effector cells that cause injury. Excessive activation of the complement system is normally prevented by a series of circulating and cell-bound complement regulatory proteins. Genetic deficiencies or mutations of these proteins can lead to the spontaneous development of glomerular disease. The identification of specific antigens in human disease may lead to the development of fundamental therapies. Particularly promising future therapeutic approaches include selective immunosuppression and interference in complement activation and C5b-9-mediated cell injury.

Signaling through up-regulated C3a receptor is key to the development of experimental lupus nephritis

Signaling of the C3a anaphylatoxin through its G protein-coupled receptor, C3aR, is relevant in a variety of inflammatory diseases, but its role in lupus nephritis is undefined. In this study, we show that expression of C3aR was significantly increased in prediseased and diseased kidneys of MRL/lpr lupus mice compared with MRL/+ controls. To investigate the role of C3aR in experimental lupus, a small molecule antagonist of C3aR (C3aRa) was administered continuously to MRL/lpr mice from 13 to 19 wk of age. All 13 C3aRa-treated mice survived during the 6-wk treatment compared with 9 of 14 (64.3%) control animals given vehicle (p = 0.019). Relative to controls, C3aRa-treated animals were protected from renal disease as measured by albuminuria (p = 0.040) and blood urea nitrogen (p = 0.021). In addition, there were fewer neutrophils, monocytes, and apoptotic cells in the kidneys of C3aRa-treated mice. C3aRa treatment also led to reduced renal IL-1beta and RANTES mRNA and phosphorylated phosphatase and tensin homologue deleted on chromosome 10 protein, whereas the mass of phosphorylated protein kinase B/Akt was increased by C3aRa. Thus, C3aR antagonism significantly reduces renal disease in MRL/lpr mice, which further translates into prolonged survival. These data illustrate that C3aR is relevant in experimental lupus nephritis and may be a target for therapeutic intervention in the human disease.

Macrophages and progressive tubulointerstitial disease

Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.

C5a receptor deficiency attenuates T cell function and renal disease in MRLlpr mice

The development and progression of systemic lupus erythematosus (SLE) is strongly associated with complement activation and deposition. To characterize the role of C5a and its receptor (C5aR) in SLE, C5aR-deficient mice were backcrossed nine generations onto the lupus-like MRL(lpr) genetic background. Evidence is presented that C5aR modulates both renal injury and T cell responses in MRL(lpr) mouse. C5aR-deficient MRL(lpr) mice had prolonged viability, with a mean survival time of 33.0 wk compared with 22.6 wk in control mice. Renal injury was also attenuated in the C5aR-/- MRL(lpr) mice. At 20 wk of age C5aR-/- MRL(lpr) mice had a complete absence of glomerular crescents and marked reductions in glomerular hypercellularity. There was no difference in the degree of glomerular C3 deposition; however, IgG deposits were reduced in the C5aR-/- MRL(lpr) mice. The reduction in glomerular injury was also associated with a four-fold decrease in renal CD4+ T cell infiltrates. Whereas there were modest differences in total IgG anti-dsDNA antibody titers, C5aR-deficient mice had 3.5-fold higher levels of IgG1 and 15-fold lower levels of IgG2a anti-dsDNA antibody titers compared to controls. The differences in anti-dsDNA IgG subclasses were associated with reduced CD4+ Th-1 responses in the C5aR-/- MRL(lpr) mice, including diminished production of IL-12p70, IFN-gamma, and increased expression of the Th-2 transcription factor GATA-3. These findings indicate that the C5aR plays a major role in modulating complement-dependent renal injury and T helper cell Th-1 responses in the MRL(lpr) mouse.

Progression in chronic kidney disease

The pathogenic mechanisms that lead to chronic kidney disease (CKD) converge on a common pathway that results in progressive interstitial fibrosis, peritubular capillary loss with hypoxia, and destruction of functioning nephrons because of tubular atrophy. Interstitial recruitment of inflammatory leukocytes and myofibroblasts occurs early in kidneys destined to develop fibrosis. Circulating monocytes are recruited by locally secreted chemoattractant molecules, facilitated by leukocyte adhesion molecules. Functionally heterogeneous macrophages secrete many fibrosis-promoting molecules, but under some circumstances they may also serve a protective scavenging role. Excessive extracellular matrix production occurs primarily within interstitial myofibroblasts, a population of cells that appears to have more than 1 origin, including the resident interstitial fibroblasts, trans-differentiated tubular epithelial cells, and bone marrow-derived cells. Impaired activity of the endogenous renal matrix-degrading proteases may enhance interstitial matrix accumulation, but the specific pathways that are involved remain unclear. Tubules, inflammatory cells, and myofibroblasts synthesize the molecules that activate the fibrogenic cascades, the most important of which is transforming growth factor beta (TGF-beta). TGF-beta may direct cells to assume a pro-fibrotic phenotype or it may do so indirectly after stimulating synthesis of other fibrogenic molecules such as connective tissue growth factor and plasminogen activator inhibitor-1. Reduced levels of antifibrotic factors that are normally produced in the kidney such as hepatocyte growth factor and bone morphogenic protein-7 may accelerate fibrosis and its destructive consequences. Development of new therapeutic agents for CKD looks promising, but several agents that target different components of the fibrogenic cascade will almost certainly be necessary.

Complement and glomerulonephritis: new insights

PURPOSE OF REVIEW

The last few years have seen a huge increase in our understanding of the role of the complement system and its regulation in glomerular disease. Our aim is to summarize the most important advances in this field.

RECENT FINDINGS

The role of complement in systemic lupus erythematosus continues to be elucidated. Classical pathway components protect from the development of autoimmunity, at least in part, through their role in the clearance of apoptotic cells. In contrast, the alternative pathway plays a direct role in exacerbating glomerular injury. Anti-C1q antibodies are related to activity in lupus nephritis and recent studies have shown that they are directly pathogenic in animal models. Proteinuria, whatever the cause, may lead to tubulointerstitial injury and complement activation adds to this process. In particular, deposition of terminal components of complement in the tubular lumen contributes to interstitial myofibroblast activation. There is increasing evidence for the role of complement regulatory proteins in glomerular injury. In particular, abnormalities of factor H or of CD46 may predispose to atypical haemolytic uraemic syndrome. The control proteins also protect against injury in immune complex glomerulonephritis.

SUMMARY

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.

C5a promotes development of experimental lupus nephritis which can be blocked with a specific receptor antagonist

The MRL/lpr murine SLE model has widespread complement activation and deposition of complement fragments in affected tissues. The potent anaphylatoxin C5a has the potential to play a key role in the pathogenesis of lupus nephritis. We found that renal expression of C5aR mRNA and protein was significantly increased in MRL/lpr mice compared to control MRL/+ mice. To examine the role of C5a signaling through C5aR, a specific small molecule antagonist (a) of C5aR was administered continuously to MRL/lpr mice from 13 to 19 wks of age. Littermate controls were given vehicle alone. The progressive impairment in renal function exhibited in the control group was prevented by C5aRa treatment. Infiltration of neutrophils and macrophages into kidneys was significantly reduced in animals treated with C5aRa compared to controls. Furthermore, renal expression of IL-1beta and MIP-2 mRNA as well as the extent of apoptosis were significantly decreased with blockade of C5aR, indicating their dependence upon signals delivered through C5aR. Thus, pharmacological blockade of C5aR reduces disease manifestations in experimental lupus nephritis. These data support an important role for the C5a anaphylatoxin in lupus nephritis, and that blockade of C5aR represents a potentially viable treatment for human lupus nephritis.

Contrasting roles of complement activation and its regulation in membranous nephropathy

The complement system is involved in defense against microorganisms, the processing of immune complexes and apoptotic debris, and the development of an appropriate immune response. Along with these physiologic effects, complement activation has the potential to result in tissue pathology. To limit this, various complement regulatory proteins (CRP) are present on host cells, including the glomerular podocyte. Experimental data from the Heymann nephritis (HN) rat model of human membranous nephropathy (MN) have shown that IgG antibodies in subepithelial immune deposits initiate complement activation and C5b-9-mediated damage of the overlying podocyte. Although IgG can activate the classical pathway, there also is evidence that alternative pathway activation occurs in MN, which could occur because of absent, dysfunctional, or inhibited podocyte CRP. Related to this are experimental data in HN showing the presence of antibodies that bind and inhibit podocyte CRP; although such antibodies have not been documented in human MN, a decrease in CR1 quantity on the podocyte has been observed. A s a result of a relative lack of CRP and the exposure of activating complement proteins to tubular cells, alternative complement pathway activation and C5b-9-mediated tubular injury can occur in MN and other proteinuric diseases. Overall, in a disease such as MN, the balance between complement regulation and activation is tipped toward its being activated. Therefore, a number of therapeutic approaches have been developed to counteract this, including recombinant forms of endogenous CRP and complement-inhibitory monoclonal antibodies. There is good reason to be optimistic that approaches to block complement activation will become viable therapy for human MN in the future.

Complement Factor H Limits Immune Complex Deposition and Prevents Inflammation and Scarring in Glomeruli of Mice with Chronic Serum Sickness

Factor H is the major complement regulator in plasma. Abnormalities in factor H have been implicated in membranoproliferative glomerulonephritis in both humans and experimental animals. It has been shown that factor H on rodent platelets functions analogously to human erythrocyte complement receptor 1 in its role to traffic immune complexes to the mononuclear phagocyte system. C57BL/6 factor H-deficient mice (Cfh(-/-)) and wild-type (wt) controls were immunized daily for 5 wk with heterologous apoferritin to study the chronic serum sickness GN model. Immunizations were started in 6- to 8-wk-old mice, which was before the development of spontaneous membranoproliferative glomerulonephritis in some Cfh(-/-) animals. Glomerular deposition of IgG immune complexes in glomeruli was qualitatively and quantitatively increased in Cfh(-/-) mice compared with wt mice. Consistent with the increase in glomerular immune complexes and possibly because of alternative pathway complement activation, Cfh(-/-) mice had increased glomerular C3 deposition. Wt mice developed no glomerular pathology. In contrast, Cfh(-/-) mice developed diffuse proliferative GN with focal crescents and glomerulosclerosis. In addition, there was significantly increased expression of collagen IV, fibronectin, and laminin mRNA in Cfh(-/-) glomeruli. These data show a role for platelet-associated factor H to process immune complexes and limit their accumulation in glomeruli. Once deposited in glomeruli, excessive complement activation can lead to glomerular inflammation and the rapid development of a scarring phenotype.

Retinoic acid treatment protects MRL/lpr lupus mice from the development of glomerular disease

BACKGROUND

Retinoic acid (tRA) is an active metabolite of vitamin A with potent anti-inflammatory properties. We analyzed the effects of tRA on the development of lupus nephritis in MRL/lpr mice.

METHODS

MRL/lpr mice received chow supplemented with vehicle or tRA (daily 10 mg/kg) from 8 to 14 weeks until their sacrifice. MRL/wt mice served as an additional control.

RESULTS

tRA-treated MRL/lpr mice showed reduced lymphoadenopathy and splenomegaly as compared to vehicle-treated controls. Treatment reduced proteinuria to almost basal levels. Plasma IgG and anti-DNA antibodies increased comparably in both vehicle and tRA-treated mice. Vehicle-treated mice showed characteristic renal lesions. In contrast tRA-treated mice showed almost normal glomerular histology with a pronounced reduction in endocapillary cell proliferation. T-cell and macrophage infiltrates were reduced after tRA treatment within glomeruli and interstitium as compared to vehicle-treated animals. In spite of this, immune complex and complement deposition were comparable in both groups. Adoptively transferred T cells from vehicle-treated to tRA-treated MRL/lpr mice did not induce renal lesions or proteinuria. These beneficial effects of tRA treatment were associated with reduced renal expression of chemokines and inflammatory cytokines. Surprisingly, renal transforming growth factor-beta (TGF-beta) mRNA levels of tRA-treated mice were elevated, possibly indicating that TGF-beta acts as an anti-inflammatory signal in this lupus model.

CONCLUSION

tRA treatment reduces lymphoproliferation and glomerulonephritis in MRL/lpr mice. This occurs in spite of unaltered anti-DNA titers and glomerular immune complex deposition, and cannot be overcome by T-cell transfer from nephritic MRL/lpr mice.

Excessive matrix accumulation in the kidneys of MRL/lpr lupus mice is dependent on complement activation

Complement receptor 1-related gene/protein y (Crry) in rodents is a potent membrane complement regulator that inhibits complement C3 activation by both classical and alternative pathways. Complement inhibition with Crry as the recombinant protein Crry-Ig has been demonstrated to prevent MRL/MpJ-Tnfrsf6(lpr) (MRL/lpr) mice from developing proteinuria and renal failure. Crry-Ig-treated mice also showed less glomerulosclerosis compared with control MRL/lpr mice. To clarify how complement inhibition with Crry might affect renal scarring in lupus nephritis, gene transcript profiling was performed comparing Crry-Ig-treated MRL/lpr mice to control-treated MRL/lpr mice as well as to the MRL/+ strain control. Altered gene expression was confirmed by quantitative PCR, and protein quantity with either immunoblotting or immunofluorescence microscopy. Collagens I, III, IV, and VI were overexpressed in control MRL/lpr mice, whereas complement inhibition with Crry reduced the overexpression of these extracellular matrix components toward normal. Plasminogen activator inhibitor 1, connective tissue growth factor, and TGF-beta1 were upregulated in MRL/lpr mice compared with MRL/+ mice and were normalized by Crry-Ig treatment, suggesting that the product of these genes may contribute to the progressive glomerulosclerosis in MRL/lpr mice in a complement-dependent fashion. Thus, complement inhibition with Crry has a prominent effect on matrix-related genes and proteins, which translates into improvement in functional renal disease.

Utility of endogenous creatinine clearance as a measure of renal function in mice

BACKGROUND

The use of endogenous plasma creatinine levels and creatinine clearance as a tool to evaluate renal function in mice has come under scrutiny as prior studies have reported that the Jaffé alkaline picrate method grossly overestimates true plasma creatinine in mice. As members of the NIDDK Animal Models of Diabetic Complications Consortium (AMDCC), we evaluated the performance and feasibility of an alternative high-performance liquid chromatography (HPLC)-based method for standard determination of plasma creatinine and creatinine clearance in mice. Our purpose was to develop a simple method that provides a reliable, reproducible, and sensitive assay for small volumes (<25 microL) of mouse plasma and sera.

METHODS

We compared creatinine clearance measured by HPLC with the Jaffé method and HPLC creatinine clearance with inulin clearance [fluoroscein isothiocyanate (FITC) inulin in an osmotic pump implanted in mouse] in C57BL/6J mice. Different groups of mice underwent either one of two protocols. Protocol A included dietary intervention with normal, low salt plus enalapril, or high salt. Protocol B induced diabetes using streptozotocin.

RESULTS

First, mean plasma creatinine levels were significantly lower (P < 0.0001) by HPLC (0.128 +/- 0.026 mg/dL) vs. Jaffé (0.4 +/- 0.12 mg/dL) for mice on a normal diet. Urine creatinine concentrations measured by HPLC were 10% lower than by Jaffé (P < 0.01). Second, mean creatinine clearance by HPLC for mice on a normal diet was 255 +/- 68 microL/min. Mice on low salt diet plus enalapril had reduced creatinine clearance (72.8 +/- 24.2 microL/min) while mice on high salt diet had an elevated creatinine clearance (355 +/- 105 microL/min). Third, diabetic mice (19 to 24 weeks of diabetes) exhibited hyperfiltration as creatinine clearance was 524 +/- 214 microL/min whereas nondiabetic age/gender-matched mice showed a mean creatinine clearance of 206 +/- 41 microL/min. Finally, significant correlation was demonstrated for creatinine clearance by HPLC vs. inulin clearance (R= 0.643; P < 0.001).

CONCLUSION

HPLC is highly accurate, much more sensitive and specific than the Jaffé method for plasma creatinine measurements in mice. Creatinine clearance in mice measured by HPLC reflects changes in renal function induced by diet and diabetes.

Overexpression of complement inhibitor Crry does not prevent cryoglobulin-associated membranoproliferative glomerulonephritis

BACKGROUND

Mice overexpressing thymic stromal lymphopoietin (TSLP) develop mixed cryoglobulinemia with renal disease closely resembling human cryoglobulin-associated membranoproliferative glomerulonephritis (MPGN), including glomerular deposits of immunoglobulins and complement. We assessed the effect of complement inhibition through overexpression of Crry (complement receptor-1 related gene/protein Y), which blocks the classic and alternative pathway of complement activation through inhibition of the C3 convertase, in cryoglobulinemia-associated immune complex glomerulonephritis.

METHODS

TSLP transgenic mice were crossbred with animals overexpressing Crry. Mice were sacrificed after 50 days (females) or 120 days (males), and kidneys, blood, and urine were collected from seven mice of each experimental group (wild type, Crry transgenic, TSLP transgenic, and Crry/TSLP doubly transgenic).

RESULTS

TSLP/Crry doubly transgenic animals demonstrated expected serum levels of Crry. Renal involvement, both in TSLP transgenic and TSLP/Crry doubly transgenic animals, was characterized by glomerular matrix expansion, macrophage influx, activation of mesangial cells, and deposition of immunoglobulins and complement. Overexpression of Crry did not result in significant improvement of renal pathology or laboratory findings. Expression of recombinant soluble Crry was confirmed by enzyme-linked immunosorbent assay (ELISA) in Crry transgenic animals. However, formation of the membrane attack complex C5b-9 as a marker of terminal active complement components and represented by glomerular C9 staining could not be inhibited in Crry transgenic TSLP mice.

CONCLUSION

These results indicate that overexpression of Crry was not sufficient to prevent renal injury in TSLP transgenic mice. We suggest that the inhibitory capacity of Crry may be overwhelmed by chronic complement activation. Further studies need to address the role of complement in cryoglobulinemic glomerulonephritis before therapeutic complement inhibition can be attempted.

Anti-C1q autoantibodies in murine lupus nephritis

Autoantibodies against C1q can be found in the circulation of patients with several autoimmune diseases including systemic lupus erythematosus (SLE). In SLE there is an association between the occurrence of these antibodies and renal involvement. How anti-C1q autoantibodies contribute to renal disease is currently unknown. Cohorts of MRL-lpr mice, which are known to develop age-dependent SLE-like disease, were used to study the relationship between levels of anti-C1q autoantibodies and renal disease. We collected serum, urine and renal tissue and analysed autoantibodies, complement levels and renal deposition as well as renal function. At 2 months of age all mice already had elevated levels of anti-C1q autoantibodies, and elution of kidneys revealed the presence of these antibodies in renal immune deposits in MRL-lpr mice and not in control MRL+/+ mice. In conclusion, anti-C1q antibodies are already present in serum and immune deposits of the kidney early in life and therefore can play a role in nephritis during experimental SLE-like disease in mice.

Recent advances in the pathogenesis of lupus nephritis: autoantibodies and b cells

Although many factors contribute to the clinical presentation and subsequent course of individuals with lupus nephritis, the formation of glomerular immune deposits is typically one of the initial events. In general, breakdown in immunologic tolerance leads to the production of autoreactive B and T cells that, either through direct infiltration and/or their secretory products, initiate inflammation. Immune deposition within glomeruli results in complement activation and recruitment of inflammatory cells, along with activation of endogenous renal cells. This inflammatory cascade leads to secretion of cytokines and chemokines, which in turn attract more infiltrating cells. Up-regulation of lymphoid-derived chemokines further enhance the cellular influx, augmenting inflammation and resulting in further tissue damage. The degree of inflammation is determined by the extent of this invasion along with both the systemic and local responses to the assault. This review focuses mainly on the contributions of pathogenic autoantibodies, autoreactive B cells to lupus nephritis, and potential immunologic therapies for lupus nephritis. Manipulation of both the cells and soluble mediators that initiate and perpetuate the disease are essential to suppressing autoreactivity and inflammation and preventing disease progression.