Th2 responses induce humorally mediated injury in experimental anti-glomerular basement membrane glomerulonephritis

Single-cell RNA Sequencing Identified Novel Nr4a1+ Ear2+ Anti-Inflammatory Macrophage Phenotype under Myeloid-TLR4 Dependent Regulation in Anti-Glomerular Basement Membrane (GBM) Crescentic Glomerulonephritis (cGN)

Previously, this study demonstrates the critical role of myeloid specific TLR4 in macrophage-mediated progressive renal injury in anti-glomerular basement membrane (anti-GBM) crescentic glomerulonephritis (cGN); however, the underlying mechanism remains largely unknown. In this study, single-cell RNA sequencing (scRNA-seq), pseudotime trajectories reconstruction, and motif enrichment analysis are used, and macrophage diversity in anti-GBM cGN under tight regulation of myeloid-TLR4 is uncovered. Most significantly, a myeloid-TLR4 deletion-induced novel reparative macrophage phenotype (Nr4a1⁺ Ear2+) with significant upregulated anti-inflammatory and tissue repair-related signaling is discovered, thereby suppressing the M1 proinflammatory responses in anti-GBM cGN. This is further demonstrated in vitro that deletion of TLR4 from bone marrow-derived macrophages (BMDMs) induces the Nr4a1/Ear2-expressing anti-inflammatory macrophages while blocking LPS-stimulated M1 proinflammatory responses. Mechanistically, activation of the Nr4a1/Ear2-axis is recognized as a key mechanism through which deletion of myeloid-TLR4 promotes the anti-inflammatory macrophage differentiation in vivo and in vitro. This is confirmed by specifically silencing macrophage Nr4a1 or Ear2 to reverse the anti-inflammatory effects on TLR4 deficient BMDMs upon LPS stimulation. In conclusion, the findings decode a previously unidentified role for a myeloid-TLR4 dependent Nr4a1/Ear2 negative feedback mechanism in macrophage-mediated progressive renal injury, implying that activation of Nr4a1-Ear2 axis can be a novel and effective immunotherapy for anti-GBM cGN.

Pathogenic T-Cell Responses in Immune-Mediated Glomerulonephritis

Glomerulonephritis (GN) comprises a group of immune-mediated kidney diseases affecting glomeruli and the tubulointerstitium. Glomerular crescent formation is a histopathological characteristic of severe forms of GN, also referred to as crescentic GN (cGN). Based on histological findings, cGN includes anti-neutrophil cytoplasmic antibody (ANCA)-associated GN, a severe form of ANCA-associated vasculitis, lupus nephritis associated with systemic lupus erythematosus, Goodpasture’s disease, and IgA nephropathy. The immunopathogenesis of cGN is associated with activation of CD4+ and CD8+ T cells, which particularly accumulate in the periglomerular and tubulointerstitial space but also infiltrate glomeruli. Clinical observations and functional studies in pre-clinical animal models provide evidence for a pathogenic role of Th1 and Th17 cell-mediated immune responses in cGN. Emerging evidence further argues that CD8+ T cells have a role in disease pathology and the mechanisms of activation and function of recently identified tissue-resident CD4+ and CD8+ T cells in cGN are currently under investigation. This review summarizes the mechanisms of pathogenic T-cell responses leading to glomerular damage and renal inflammation in cGN. Advanced knowledge of the underlying immune mechanisms involved with cGN will enable the identification of novel therapeutic targets for the replacement or reduction in standard immunosuppressive therapy or the treatment of refractory disease.

Cruzipain Sulfotopes-Specific Antibodies Generate Cardiac Tissue Abnormalities and Favor Trypanosoma cruzi Infection in the BALB/c Mice Model of Experimental Chagas Disease

Trypanosoma cruzi cruzipain (Cz) bears a C-terminal domain (C-T) that contains sulfated epitopes “sulfotopes” (GlcNAc6S) on its unique N-glycosylation site. The effects of in vivo exposure to GlcNAc6S on heart tissue ultrastructure, immune responses, and along the outcome of infection by T. cruzi, were evaluated in a murine experimental model, BALB/c, using three independent strategies. First, mice were pre-exposed to C-T by immunization. C-T-immunized mice (C-T_IM) showed IgG2a/IgG1 <1, induced the production of cytokines from Th2, Th17, and Th1 profiles with respect to those of dC-T_IM, which only induced IL-10 respect to the control mice. Surprisingly, after sublethal challenge, both C-T_IM and dC-T_IM showed significantly higher parasitemia and mortality than the control group. Second, mice exposed to BSA-GlcNAc6S as immunogen (BSA-GlcNAc6S_IM) showed: severe ultrastructural cardiac alterations while BSA-GlcNAc_IM conserved the regular tissue architecture with slight myofibril changes; a strong highly specific humoral-immune-response reproducing the IgG-isotype-profile obtained with C-T_IM; and a significant memory-T-cell-response demonstrating sulfotope-immunodominance with respect to BSA-GlcNAc_IM. After sublethal challenge, BSA-GlcNAc6S_IM showed exacerbated parasitemias, despite elevated IFN-γ levels were registered. In both cases, the abrogation of ultrastructural alterations when using desulfated immunogens supported the direct involvement of sulfotopes and/or indirect effect through their specific antibodies, in the induction of tissue damage. Finally, a third strategy using a passive transference of sulfotope-specific antibodies (IgG-GlcNAc6S) showed the detrimental activity of IgG-GlcNAc6S on mice cardiac tissue, and mice treated with IgG-GlcNAc6S after a sublethal dose of T. cruzi, surprisingly reached higher parasitemias than control groups. These findings confirmed the indirect role of the sulfotopes, via their IgG-GlcNAc6S, both in the immunopathogenicity as well as favoring T. cruzi infection.

Regulatory role and mechanisms of myeloid TLR4 in anti-GBM glomerulonephritis

Myeloid cells and TLR4 play a critical role in acute kidney injury. This study investigated the regulatory role and mechanisms of myeloid TLR4 in experimental anti-glomerular basement membrane (GBM) glomerulonephritis (GN). Anti-GBM GN was induced in tlr4^flox/flox and tlr4^{flox/flox−lysM−cre} mice by intravenous injection of the sheep anti-mouse GBM antibody. Compared to control mice, conditional disruption of tlr4 from myeloid cells, largely macrophages (> 85%), suppressed glomerular crescent formation and attenuated progressive renal injury by lowering serum creatinine and 24-h urine protein excretion while improving creatinine clearance. Mechanistically, deletion of myeloid tlr4 markedly inhibited renal infiltration of macrophages and T cells and resulted in a shift of infiltrating macrophages from F4/80⁺iNOS⁺ M1 to F4/80⁺CD206⁺ M2 phenotype and inhibited the upregulation of renal proinflammatory cytokines IL-1β and MCP-1. Importantly, deletion of myeloid tlr4 suppressed T cell-mediated immune injury by shifting Th1 (CD4⁺IFNγ⁺) and Th17 (CD4⁺IL-17a⁺) to Treg (CD4⁺CD25⁺FoxP3⁺) immune responses. Transcriptome analysis also revealed that disrupted myeloid TLR4 largely downregulated genes involving immune and cytokine-related pathways. Thus, myeloid TLR4 plays a pivotal role in anti-GBM GN by immunological switching from M1 to M2 and from Th1/Th17 to Treg and targeting myeloid TLR4 may be a novel therapeutic strategy for immune-mediated kidney diseases.

Re-Examining Neutrophil Participation in GN

Significant advances in understanding the pathogenesis of GN have occurred in recent decades. Among those advances is the finding that both innate and adaptive immune cells contribute to the development of GN. Neutrophils were recognized as key contributors in early animal models of GN, at a time when the prevailing view considered neutrophils to function as nonspecific effector cells that die quickly after performing antimicrobial functions. However, advances over the past two decades have shown that neutrophil functions are more complex and sophisticated. Specifically, research has revealed that neutrophil survival is regulated by the inflammatory milieu and that neutrophils demonstrate plasticity, mediate microbial killing through previously unrecognized mechanisms, demonstrate transcriptional activity leading to the release of cytokines and chemokines, interact with and regulate cells of the innate and adaptive immune systems, and contribute to the resolution of inflammation. Therefore, neutrophil participation in glomerular diseases deserves re-evaluation. In this review, we describe advances in understanding classic neutrophil functions, review the expanded roles of neutrophils in innate and adaptive immune responses, and summarize current knowledge of neutrophil contributions to GN.

Peptidylarginine Deiminase Inhibitor Suppresses Neutrophil Extracellular Trap Formation and MPO-ANCA Production

Myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis is a systemic small-vessel vasculitis, wherein, MPO-ANCA plays a critical role in the pathogenesis. Neutrophil extracellular traps (NETs) released from activated neutrophils are composed of extracellular web-like DNA and antimicrobial proteins, including MPO. Diverse stimuli, such as phorbol myristate acetate (PMA) and ligands of toll-like receptors (TLR), induce NETs. Although TLR-mediated NET formation can occur with preservation of living neutrophilic functions (called vital NETosis), PMA-stimulated neutrophils undergo cell death with NET formation (called suicidal NETosis). In the process of suicidal NETosis, histones are citrullinated by peptidylarginine deiminase 4 (PAD4). Since this step is necessary for decondensation of DNA, PAD4 plays a pivotal role in suicidal NETosis. Although NETs are essential for elimination of microorganisms, excessive formation of NETs has been suggested to be implicated in MPO-ANCA production. This study aimed to determine if pan-PAD inhibitors could suppress MPO-ANCA production in vivo. At first, NETs were induced in peripheral blood neutrophils derived from healthy donors (1 × 10⁶/ml) by stimulation with 20 nM PMA with or without 20 μM propylthiouracil (PTU), an anti-thyroid drug. We then determined that the in vitro NET formation was inhibited completely by 200 μM Cl-amidine, a pan-PAD inhibitor. Next, we established mouse models with MPO-ANCA production. BALB/c mice were given intraperitoneal (i.p.) injection of PMA (50 ng at days 0 and 7) and oral PTU (2.5 mg/day) for 2 weeks. These mice were divided into two groups; the first group was given daily i.p. injection of PBS (200 μl/day) (n = 13) and the other group with daily i.p. injection of Cl-amidine (0.3 mg/200 μl PBS/day) (n = 7). Two weeks later, citrullination as an indicator of NET formation in the peritoneum and serum MPO-ANCA titer was compared between the two groups. Results demonstrated that citrullination in the peritoneum was significantly reduced in the Cl-amidine-treated mice compared with the vehicle-injected control mice (38% reduction). Additionally, the serum MPO-ANCA titer of the Cl-amidine-treated mice (32.3 ± 31.0 ng/ml) was significantly lower than that in the vehicle-injected mice (132.1 ± 41.6 ng/ml). The collective findings indicate that excessive formation of NETs may be implicated in MPO-ANCA production in vivo.

Glomerulonephritis Induced by Heterologous Anti-GBM Globulin as a Planted Foreign Antigen

The glomerulonephritides are diseases characterized by immune-mediated glomerular inflammation. Most severe and rapidly progressive forms of glomerulonephritis feature the participation of injurious leukocytes that localize to glomeruli. This unit describes classical models of rapidly progressive glomerulonephritis in mice, induced by injecting heterologous globulin (raised in sheep) that binds to the glomerular basement membrane. These models have been particularly useful in defining the participation of effector leukocytes in severe glomerular disease. In these models, injury typically occurs in two phases. In the initial, heterologous phase, injury is mediated by the globulin bound within the glomerulus acting as an antibody. The later, autologous phase of injury is mediated by the host's adaptive immunity to the heterologous globulin now functioning as a planted foreign antigen within glomeruli. As autologous phase injury is driven by immunity to sheep globulin, assessment of antigen-specific systemic immunity to sheep globulin is critical when using this model.

Granulocyte-dependent autoantibody-induced skin blistering

Autoimmune phenomena occur in healthy individuals, but when self-tolerance fails, the autoimmune response may result in specific pathology. According to Witebsky's postulates, one of the criteria in diagnosing a disease as autoimmune is the reproduction of the disease in experimental animals by the passive transfer of autoantibodies. For epidermolysis bullosa acquisita (EBA), a prototypic organ-specific autoimmune disease of skin and mucous membranes, several experimental models were recently established. In the animal model described in our present work, purified IgG antibodies against a stretch of 200 amino acids (aa 757-967) of collagen VII are injected repeatedly into mice reproducing the blistering phenotype as well as the histo- and immunopathological features characteristic to human EBA (1). Full-blown widespread disease is usually seen 5-6 days after the first injection and the extent of the disease correlates with the dose of the administered collagen VII-specific IgG. The tissue damage (blister formation) in the experimental EBA is depending on the recruitment and activation of granulocytes by tissue-bound autoantibodies (2,-4). Therefore, this model allows for the dissection of the granulocyte-dependent inflammatory pathway involved in the autoimmune tissue damage, as the model reproduces only the T cell-independent phase of the efferent autoimmune response. Furthermore, its value is underlined by a number of studies demonstrating the blister-inducing potential of autoantibodies in vivo and investigating the mechanism of the blister formation in EBA (1,3,-6). Finally, this model will greatly facilitate the development of new anti-inflammatory therapies in autoantibody-induced diseases. Overall, the passive transfer animal model of EBA is an accessible and instructive disease model and will help researchers to analyze not only EBA pathogenesis but to answer fundamental biologically and clinically essential autoimmunity questions.

The sphingosine-1-phosphate receptor agonist FTY720 prevents the development of anti-glomerular basement membrane glomerulonephritis

The sphingosine-1-phosphate (S1P) agonist FTY720 prolongs the survival of organ allograft and attenuates autoimmune-mediated injury in experimental models. Most cases of glomerulonephritis (GN) in human appear to be immunologically initiated. In this study, we evaluated the potential therapeutic role of FTY720 in GN via a mouse anti-glomerular basement membrane (GBM) model. Mice were immunized with rabbit IgG in complete Freund's adjuvant (CFA) followed by an intravenous injection of a rabbit anti-mouse GBM serum. Disease and immune responses were assessed on day 14. Mice were treated with FTY720 (0.3 or 3 mg/kg) and prednisone (10 mg/kg) from days 0 to 14. The S1P modulator reduced proteinuria, serum creatinine, crescent formation and serum IgG level. The expressions of splenic S1P receptor and renal Th-1 cytokine were also inhibited at the transcription stage. Treatment with FTY720 increased splenocyte production of protective Th2 cytokine IL-4 and promoted the apoptosis of splenic CD4+ T cells in the animal models, which suggests that FTY720 played a protective role at the induction stage of GN by inhibiting mRNA expressions of splenic S1P receptor 1, S1P receptor 2, and S1P receptor 5.

The neonatal Fc receptor as therapeutic target in IgG-mediated autoimmune diseases

Therapy approaches based on lowering levels of pathogenic autoantibodies represent rational, effective, and safe treatment modalities of autoimmune diseases. The neonatal Fc receptor (FcRn) is a major factor regulating the serum levels of IgG antibodies. While FcRn-mediated half-life extension is beneficial for IgG antibody responses against pathogens, it also prolongs the serum half-life of IgG autoantibodies and thus promotes tissue damage in autoimmune diseases. In the present review article, we examine current evidence on the relevance of FcRn in maintaining high autoantibody levels and discuss FcRn-targeted therapeutic approaches. Further investigation of the FcRn-IgG interaction will not only provide mechanistic insights into the receptor function, but should also greatly facilitate the design of therapeutics combining optimal pharmacokinetic properties with the appropriate antibody effector functions in autoimmune diseases.

Focal and segmental glomerulosclerosis induced in mice lacking decay-accelerating factor in T cells

Heritable and acquired diseases of podocytes can result in focal and segmental glomerulosclerosis (FSGS). We modeled FSGS by passively transferring mouse podocyte-specific sheep Abs into BALB/c mice. BALB/c mice deficient in the key complement regulator, decay-accelerating factor (DAF), but not WT or CD59-deficient BALB/c mice developed histological and ultrastructural features of FSGS, marked albuminuria, periglomerular monocytic and T cell inflammation, and enhanced T cell reactivity to sheep IgG. All of these findings, which are characteristic of FSGS, were substantially reduced by depleting CD4+ T cells from Daf(-/-) mice. Furthermore, WT kidneys transplanted into Daf(-/-) recipients and kidneys of DAF-sufficient but T cell-deficient Balb/(cnu/nu) mice reconstituted with Daf(-/-) T cells developed FSGS. In contrast, DAF-deficient kidneys in WT hosts and Balb/(cnu/nu) mice reconstituted with DAF-sufficient T cells did not develop FSGS. Thus, we have described what we believe to be a novel mouse model of FSGS attributable to DAF-deficient T cell immune responses. These findings add to growing evidence that complement-derived signals shape T cell responses, since T cells that recognize sheep Abs bound to podocytes can lead to cellular injury and development of FSGS.

DNA epitope vaccine containing complement component C3d enhances anti-amyloid-beta antibody production and polarizes the immune response towards a Th2 phenotype

We have engineered a DNA epitope vaccine that expresses 3 self-B cell epitopes of Abeta(42) (3Abeta(1-11)), a non-self T helper (Th) cell epitope (PADRE), and 3 copies of C3d (3C3d), a component of complement as a molecular adjuvant, designed to safely reduce CNS Abeta. Immunization of mice with 3Abeta(1-11)-PADRE epitope vaccine alone generated only moderate levels of anti-Abeta antibodies and a pro-inflammatory T helper (Th1 phenotype) cellular immune response. However, the addition of 3C3d to the vaccine construct significantly augmented the anti-Abeta humoral immune response and, importantly, shifted the cellular immune response towards the potentially safer anti-inflammatory Th2 phenotype.

Interferon-beta reduces proteinuria in experimental glomerulonephritis

Interferon-beta (IFN-beta) is a multifunctional cytokine with immunomodulatory properties. We examined the effect of IFN-beta in three separate rat models of glomerular injury and in cultured human glomerular endothelial cells and podocytes. In nephrotoxic nephritis in WKY rats, recombinant rat IFN-beta started either at induction or after establishment of disease significantly reduced 24-h proteinuria by up to 73% and 51%, respectively, but did not affect serum creatinine. There was a slight reduction in numbers of glomerular macrophages, but no difference in glomerular or tubulointerstitial scarring. In Thy-1 nephritis in Lewis rats, IFN-beta started at induction of disease reduced proteinuria by up to 66% with no effect on numbers of glomerular macrophages, but a reduced number of proliferating cells. In puromycin nephropathy in Wistar rats, IFN-beta started at induction of disease reduced proteinuria by up to 93%, but had no effect on glomerular histology. In cultured cells, human IFN-beta-1a had a dramatic effect on barrier properties, increasing electrical resistance across monolayers of either glomerular endothelial cells or podocytes and decreasing trans-monolayer passage of albumin. In conclusion, these results show that IFN-beta reduces proteinuria in three different rat models of glomerular injury and that its anti-proteinuric action may result from direct effects on cells that comprise the glomerular filtration barrier. These data indicate that IFN-beta may have potential as a therapeutic agent in proteinuric renal disease.

A new mouse model of immune-mediated podocyte injury

Podocytes play a major role in the initiation and progression of glomerular diseases and are a target of both immune-mediated and non-immune-mediated injury. To establish a mouse model of such injury, we preimmunized mice with Freunds adjuvant 5 days before intravenous injection of a rabbit polyclonal antibody directed against a murine podocyte cell line. For the next 7 weeks, we collected urine, serum, and kidney samples. Nephritic animals developed severe albuminuria, which was maximal on day 10. Histochemistry revealed diffuse mesangial matrix expansion. Mouse immunoglobulin G and complement were detected in a linear pattern along the glomerular filtration barrier and in the mesangial hinge region. Complement depletion, however, did not prevent proteinuria. Glomerular T cells were increased, whereas podocytes were significantly reduced. Glomerular foot processes were flattened in regions with mesangial matrix deposition as viewed by electron microscopy. Immunohistochemistry detected the injected anti-podocyte antibody exclusively at the glomerular tuft on all days examined. Immunoelectron microscopy localized the antibody to podocyte foot processes and the glomerular basement membrane, which was morphologically intact. This suggests that the podocyte was the main target of the antiserum. Our study establishes a new mouse model of immune-mediated podocyte injury.

Leukocyte recruitment to the inflamed glomerulus: a critical role for platelet-derived P-selectin in the absence of rolling

The renal glomerulus is one of the few sites within the microvasculature in which leukocyte recruitment occurs in capillaries. However, due to the difficulty of directly visualizing the glomerulus, the mechanisms of leukocyte recruitment to glomerular capillaries are poorly understood. To overcome this, we rendered murine kidneys hydronephrotic to allow the visualization of the functional glomerular microvasculature during an inflammatory response. These experiments demonstrated that following infusion of anti-glomerular basement membrane (GBM) Ab, leukocytes became adherent in glomerular capillaries via a process of immediate arrest, without undergoing prior detectable rolling. However, despite the absence of rolling, this recruitment involved nonredundant roles for the P-selectin/P-selectin glycoprotein ligand-1 and beta2 integrin/ICAM-1 pathways, suggesting that a novel form of the multistep leukocyte adhesion cascade occurs in these vessels. Anti-GBM Ab also increased glomerular P-selectin expression and induced a P-selectin-independent increase in platelet accumulation. Moreover, platelet depletion prevented both the increase in glomerular P-selectin, and the leukocyte recruitment induced by anti-GBM Ab. Furthermore, depletion of neutrophils and platelets also prevented the increase in urinary protein excretion induced by anti-GBM Ab, indicating that their accumulation in glomeruli contributed to the development of renal injury. Finally, infusion of wild-type platelets into P-selectin-deficient mice restored the ability of glomeruli in these mice to support leukocyte adhesion. Together, these data indicate that anti-GBM Ab-induced leukocyte adhesion in glomeruli occurs via a novel pathway involving a nonrolling interaction mediated by platelet-derived P-selectin.

Accumulation of immune complexes in glomerular disease is independent of locally synthesized c3

Although complement activation can make immune complex glomerulonephritis worse, the third complement component also can solubilize immune complexes and thus reduce the severity of disease. How C3 that is produced within the kidney contributes to this balance is unknown. This study therefore investigated the relative roles of systemic and local C3 production in a model of glomerular immune complex disease. Injection of sheep anti-glomerular basement membrane antibody into preimmunized mice resulted in accumulation of immune complexes and progressive loss of function over 14 d that was much more marked in C3-deficient (C3-/-) mice. In C3-sufficient mice that received a transplant of a C3-/- mouse kidney and in C3-/- mice with C3-sufficient mouse kidney transplants, the severity and the pattern of injury went with the complement status of the recipient. That is, mice with deficient circulating C3 developed severe glomerular immune complex disease, whereas those with a high level of circulating C3 had well-preserved glomerular structure and function. It is concluded that circulating C3 is a critical factor in reducing the glomerular accumulation of immune complexes. Local synthesis of C3 did not have a major influence on this aspect of glomerular disease.

Interleukin-11 reduces renal injury and glomerular NF-kappa B activity in murine experimental glomerulonephritis

BACKGROUND/AIMS

There is now considerable evidence implicating T cells and macrophages in glomerular injury in crescentic glomerulonephritis. Recently, it has been shown that interleukin-11 (IL-11) has an immune modulatory function through its effect on both macrophages and T cells. We, therefore, examined the therapeutic effect of IL-11 in a murine model of experimental glomerulonephritis.

METHOD

Accelerated nephrotoxic nephritis was induced in C57BL/6 mice. IL-11 at a dose of 0.5 mg/kg/day (n = 10) in vehicle was given daily subcutaneously from the day of sensitization until day 14 after initiation of glomerulonephritis. Control mice (n = 10) received injection of vehicle alone with the same schedule.

RESULTS

IL-11 treatment markedly decreased albuminuria (6.2 +/- 1.9 vs. 18.2 +/- 4.5 mg/day, p < 0.05), the number of glomerular macrophages (1.1 +/- 0.2 vs. 1.7 +/- 0.3 cells/glomerular cross-section, p < 0.05) and glomerular fibrin deposition (fibrin score 0.9 +/- 0.3 vs. 2 +/- 0.3, p < 0.05). There was no difference in the glomerular T cell numbers between the IL-11-treated and the vehicle group. Glomerular NF-kappaB activity was markedly suppressed by 75% in the treated group (p = 0.0015).

CONCLUSION

In this study, we provide the first in vivo evidence that IL-11 treatment decreases glomerular NF-kappaB activity and reduces renal injury in experimental glomerulonephritis.

Experimental autoimmune Goodpasture's disease: a pathogenetic role for both effector cells and antibody in injury

BACKGROUND

Goodpasture's disease [antiglomerular basement membrane (GBM) glomerulonephritis] is a classic autoimmune disease and the only organ-specific autoimmune renal disease in which the antigen is well described. The importance of antibodies against the non-collagenous domain of the alpha3 chain of type IV collagen [alpha3(IV)NC1] is well established. However, observational human studies and studies in experimental systems also imply a role for cell-mediated effector injury.

METHODS

Active experimental autoimmune glomerulonephritis (EAG) was induced by immunization with alpha3-alpha5(IV)NC1 heterodimers in B cell intact C57BL/6 mice and B cell (mu chain-deficient) mice. Passive disease was induced by transferring sera from B cell intact and B cell deficient mice with EAG to RAG-1-/- mice (that lack adaptive immunity). Histologic and functional injury was studied.

RESULTS

Despite the absence of B cells and immunoglobulin in B-cell-deficient mice, histologic and functional injury developed in mice immunized with alpha3-alpha5(IV)NC1, with T cells and macrophages in glomeruli. Injury occurred to a similar degree to that found in B-cell-intact mice. Transfer of sera from B-cell-intact mice with EAG containing antibodies (but not from B-cell-deficient mice with EAG) to RAG-1-/- mice induced linear immunoglobulin deposits on the glomerular basement membrane (GBM) and pathologic proteinuria.

CONCLUSION

Both cell-mediated and humoral effectors are capable of inducing renal injury in EAG. Given the similarity of the disease-initiating antigen in this model to the antigen in human anti-GBM glomerulonephritis, similar overlapping mechanisms are likely to operate in human disease.

IL-12p40 and IL-18 in crescentic glomerulonephritis: IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 promotes local inflammation and leukocyte recruitment

Experimental crescentic glomerulonephritis (GN) is characterized by T helper 1 (Th1) directed nephritogenic immune responses and cell-mediated glomerular injury. IL-12p40, the common cytokine chain for both IL-12 and IL-23, is important in the generation and potentially the maintenance of Th1 responses, whereas IL-18 is a co-factor for Th1 responses that may have systemic and local proinflammatory effects. For testing the hypothesis that both endogenous IL-12p40 and endogenous IL-18 play pathogenetic roles in crescentic GN, accelerated anti-glomerular basement membrane GN was induced in mice genetically deficient in IL-12p40 (IL-12p40-/-), IL-18 (IL-18-/-), or both IL-12p40 and IL-18 (IL-12p40-/-IL-18-/-). Compared with wild-type C57BL/6 mice, IL-12p40-/- mice failed to make a nephritogenic Th1 response and developed markedly reduced crescent formation and renal leukocytic infiltration, despite renal production of chemoattractants and adhesion molecules. IL-18-/- mice developed an intact antigen-specific systemic Th1 response, a similar degree of crescent formation, but fewer glomeruli affected by other severe histologic changes and fewer leukocytes in glomeruli and interstitium. IL-18 was expressed within diseased kidneys. Local production of TNF, IL-1beta, IFN-gamma, CCL3 (MIP-1alpha), and CCL4 (MIP-1beta) was reduced in IL-18-/- mice, demonstrating a local proinflammatory role for IL-18. Combined deletion of IL-12p40 and IL-18 did not result in synergistic effects. Consistent with the hypothesis that inflammation leads to fibrosis, all three groups of deficient mice expressed lower levels of intrarenal TGF-beta1 and/or alpha1(I) procollagen mRNA. These studies demonstrate that in severe experimental crescentic GN, IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 has local proinflammatory roles.

Effects of double blockade of CD28 and inducible-costimulator signaling on anti–glomerular basement membrane glomerulonephritis

Inducible costimulator (ICOS) is the third member of the CD28 superfamily, expressed on antigen-primed T-cells, enhancing Th2 differentiation. Anti-glomerular basement membrane (anti-GBM) glomerulonephritis results from multiple effects generated by both Th1 and Th2 cells. To evaluate the contribution of these T-cells to the progression of anti-GBM glomerulonephritis, we investigated the effect of double blockade of CD28 and ICOS signaling. Anti-GBM glomerulonephritis was induced in C57BL/6 mice, a Th1-prone strain. CD28 signaling was inhibited with the use of fusion proteins of cytolytic T-lymphocyte-associated antigen-4 (CTLA4 immunoglobulin) and ICOS signaling by the monoclonal antibody (mAb) for ICOS. Blood and urine samples were collected 5 and 14 days after induction of anti-GBM glomerulonephritis. Mice were killed to facilitate histopathologic analyses at the same time. Anti-GBM glomerulonephritis was prevented from functionally deteriorating (eg, proteinuria or increasing serum creatinine) by CTLA4 immunoglobulin or anti-activation-inducible lymphocyte immunomodulatory molecule (AILIM) mAb as an anti-ICOS mAb. Nevertheless, double or single blockade of ICOS signaling showed a weaker inhibitory effect than single blockade of CD28 signaling in terms of the serum immunoglobulin level and histopathologic change. There is no synergistic effect between CTLA4 immunoglobulin and anti-AILIM mAb when simultaneously administered in experimental anti-GBM glomerulonephritis. Double blockade of both CD28 signaling and ICOS signaling is effective for preventing functional deterioration in this model. However, CD28 single blockade is more effective than double blockade both serologically and histopathologically.

Histopathology of humorally mediated anti-glomerular basement membrane (GBM) glomerulonephritis in mice

BACKGROUND

From a diagnostic point of view it would be important to learn more about the relationship between the immune responses underlying glomerulonephritis and the patterns of glomerular lesions. A murine model of anti-GBM glomerulonephritis in which inflammation is driven by delayed-type hypersensitivity (DTH) has been studied extensively. The aim of this study was to uncover histological features that might be specific for anti-GBM glomerulonephritis driven by a humoral immune response.

METHODS

BALB/c mice were immunized with rabbit IgG in incomplete Freund's adjuvant. Six days later, on day 0, they received rabbit anti-GBM serum intravenously. Proteinuria was assessed with dipsticks. Mice were killed on days 4, 8 or 14. Kidneys from days 4 and 8 were processed for immunofluorescence and histology. On day 14 mice were perfusion-fixed for electron microscopy.

RESULTS

Proteinuria started on day 3. Autologous IgG and of C3 were found along the GBM. There was only slight infiltration with macrophages and no measurable infiltration by CD4 T cells, indicating the virtual absence of DTH. Besides infiltration with neutrophils there were little histological alterations on day 4. On day 8 many loops were hyalinized. On day 14, cellular crescents were found in 23% of glomeruli. Subendothelial spaces contained hyaline material, cells and fibrin. Podocytes displayed effacement of foot processes and apical microprotrusions. Podocyte bridges were common. These alterations were identical to those reported in the standard model that produces a DTH-like inflammation.

CONCLUSION

The qualitative pattern of histological damage in a murine model of anti-GBM glomerulonephritis does not depend on the underlying immunological process.

CD59a deficiency exacerbates accelerated nephrotoxic nephritis in mice

CD59 is a complement regulatory protein that inhibits the terminal part of the complement system, the membrane attack complex (MAC), a mediator of renal injury. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in experimentally induced accelerated nephrotoxic nephritis, a model of immune complex-mediated glomerulonephritis. After accelerated nephrotoxic nephritis was induced by administration of sheep nephrotoxic globulin, mCd59a-/- mice and strain-matched controls on two genetic backgrounds, 129/Sv x C57BL/6 and 129/Sv, were examined. For both, mCd59a-/- mice developed significantly greater glomerular cellularity than wild-type (WT) mice at day 5 after administration. At day 10 post-administration, mCd59a-/- mice exhibited more glomerular thrombosis than WT mice (thrombosis score, 1.8 [range, 1.4 to 4.0] versus 0.8 [range, 0.2 to 1.5] quadrants thrombosed per glomerulus, respectively; P = 0.0006). In the majority of experiments, mCd59a-/- mice also had significantly more proteinuria than controls; however, there was no difference in serum creatinine or albumin. Quantitative immunofluorescence of kidney sections revealed significantly more C9 (as a marker of MAC) deposition within glomeruli of mCd59a-/- mice than WT controls (P < 0.001). There was no difference in deposition of C3 and sheep IgG between the two experimental groups. The lack of CD59a, by allowing unregulated MAC deposition, exacerbates the renal injury in this model of immune complex-mediated glomerulonephritis.

Lack of C3 affects Th2 response development and the sequelae of chemotherapy in schistosomiasis

The role of the third component of complement (C3) during schistosome infection was investigated using mice deficient in C3. While no effect was observed 8 wk after infection on worm development or liver pathology, Ag-specific Th2-associated cytokine production (IL-13, IL-5, IL-6, and IL-10) was significantly reduced, and IFN-gamma production was enhanced in the absence of C3. IgG1 and IgE, but not IgG2a or IgM, Ab responses were also significantly impaired in infected C3(-/-) mice, suggesting that C3 may play a role in IL-4-mediated Th2 response enhancement during schistosome infection. Furthermore, C3-deficient mice could not effectively clear adult worms after praziquantel (PZQ) treatment and suffered increased morbidity due to the overproduction of proinflammatory mediators following drug administration. However, the ischemic liver damage that normally accompanies PZQ administration in infected wild-type mice was substantially reduced in treated C3-deficient mice, probably due to the absence of dead or dying worms in the livers of these animals. Together these results indicate that C3 enhances Th2 responses during schistosome infection, potentiates PZQ-mediated parasite clearance, and reduces chemotherapy-induced proinflammatory mediator production.

Effects of CTLA4-Fc on glomerular injury in humorally-mediated glomerulonephritis in BALB/c mice

The effect of cytotoxic T-lymphocyte-associated molecule 4-immunoglobulin fusion protein (CTLA4-Fc) on humorally-mediated glomerulonephritis was studied in accelerated anti-glomerular basement membrane (anti-GBM) glomerulonephritis induced in BALB/c mice. This strain of mice develops antibody and complement dependent glomerulonephritis under this protocol. Sensitized BALB/c mice developed high levels of circulating autologous antibody titres, intense glomerular deposition of mouse immunoglobulin and complement, significant proteinuria, renal impairment, significant glomerular necrosis and a minor component of crescent formation 10 days after challenge with a nephritogenic antigen (sheep anti-GBM globulin). Early treatment during the primary immune response, or continuous treatment throughout the disease with CTLA4-Fc, significantly suppressed mouse anti-sheep globulin antibody titres in serum, and immunoglobulin and complement deposition in glomeruli. The degree of glomerular necrosis was improved and proteinuria was reduced, particularly in the earlier stages of disease. Late treatment by CTLA4-Fc starting one day after challenge with sheep anti-mouse GBM did not affect antibody production and did not attenuate glomerulonephritis. The low level of crescent formation found in BALB/c mice developing glomerulonephritis was not prevented by the administration of CTLA4-Fc. These results demonstrate that CTLA4-Fc is of benefit in this model of glomerulonephritis by its capacity to attenuate antibody production, without affecting the minor degree of cell-mediated glomerular injury.

The requirement for granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor in leukocyte-mediated immune glomerular injury

Proliferative glomerulonephritis in humans is characterized by the presence of leukocytes in glomeruli. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) can potentially stimulate or affect T cell, macrophage, and neutrophil function. To define the roles of GM-CSF and G-CSF in leukocyte-mediated glomerulonephritis, glomerular injury was studied in mice genetically deficient in either GM-CSF (GM-CSF -/- mice) or G-CSF (G-CSF -/- mice). Two models of glomerulonephritis were studied: neutrophil-mediated heterologous-phase anti-glomerular basement membrane (GBM) glomerulonephritis and T cell/macrophage-mediated crescentic autologous-phase anti-GBM glomerulonephritis. Both GM-CSF -/- and G-CSF -/- mice were protected from heterologous-phase anti-GBM glomerulonephritis compared with genetically normal (CSF WT) mice, with reduced proteinuria and glomerular neutrophil numbers. However, only GM-CSF -/- mice were protected from crescentic glomerular injury in the autologous phase, whereas G-CSF -/- mice were not protected and in fact had increased numbers of T cells in glomeruli. Humoral responses to the nephritogenic antigen were unaltered by deficiency of either GM-CSF or G-CSF, but glomerular T cell and macrophage numbers, as well as dermal delayed-type hypersensitivity to the nephritogenic antigen, were reduced in GM-CSF -/- mice. These studies demonstrate that endogenous GM-CSF plays a role in experimental glomerulonephritis in both the autologous and heterologous phases of injury.

Interleukin-11 attenuates nephrotoxic nephritis in Wistar Kyoto rats

Interleukin-11 (IL-11) is a multifuctional cytokine with anti-inflammatory activity. The effect of IL-11 was studied in an experimental model of necrotizing glomerulonephritis induced in Wistar Kyoto rats by an injection of anti-glomerular basement membrane antibody (nephrotoxic serum). Intraperitoneal injection was chosen as the route of IL-11 administration in all experiments. In experiment 1, recombinant human IL-11 (1360 microg) was given 2 h before nephrotoxic serum, then once daily until day 6. In experiment 2, a lower dose of IL-11 (800 microg/d) was used. Rats were treated either with IL-11 400 microg twice daily intraperitoneally or with 800 microg once daily intraperitoneally for 6 d. In experiment 3, the lower dose of IL-11 was given 2 h before nephrotoxic serum, then twice daily until day 2. In experiment 1, IL-11 significantly reduced proteinuria (13.2 +/- 3.3 versus 63.2 +/- 4.3 mg/24 h), fibrinoid necrosis (0.58 +/- 0.08 versus 1.52 +/- 0.06 quadrants/glomerular cross section [gcs]), macrophage infiltration (ED1-positive cells, 24.4 +/- 1.8 versus 39.3 +/- 1.9 cells/gcs), apoptosis (1.11 +/- 0.1 versus 2.39 +/- 0.2 apoptotic bodies/gcs), and proliferating cell nuclear antigen-positive cells (24.4 +/- 2.0 versus 37.3 +/- 2.3 cells/gcs). Inducible nitric oxide synthase-positive cells were significantly increased (3.1 +/- 0.3 versus 2.0 +/- 0.2 cells/gcs). In experiment 2, a lower dose of IL-11 significantly reduced proteinuria and fibrinoid necrosis. Macrophage infiltration was similar in treated and control groups, although the number of sialoadhesin-positive macrophages (ED3+) was significantly reduced in the IL-11-treated rats. In experiment 3, quantitative competitive reverse transcriptase-polymerase chain reaction showed that the mRNA ratio of IL-1 beta/beta-actin in the treated rats was reduced compared with controls. By the use of probes designed from mouse IL-11 receptor alpha-chain sequence, it was also shown that rat mesangial cells and macrophages expressed IL-11 receptor alpha-chain, demonstrating that they were capable of responding to IL-11. In this model of necrotizing glomerulonephritis, high-dose IL-11 treatment markedly reduced both proteinuria and fibrinoid necrosis. At the lower dose, there was a reduction in glomerular injury and macrophage sialoadhesin expression, but without an alteration of macrophage numbers, suggesting that IL-11 may be acting in part to reduce macrophage activation.

Accelerated nephrotoxic nephritis is exacerbated in C1q-deficient mice

C1q deficiency strongly predisposes to the development of systemic lupus erythematosus in humans and mice. We used the model of accelerated nephrotoxic nephritis in C1q-deficient mice to explore the mechanisms behind these associations. C1q-deficient mice developed severe glomerular thrombosis within 4 days of induction of disease, whereas wild-type mice developed mild injury. These findings suggest that C1q protects from immune-mediated glomerular injury. This exacerbated thrombosis was also seen in mice triply deficient in C1q, factor B, and C2, excluding a major pathogenic role for the alternative pathway of complement in this phenomenon. However, these mice did not develop elevated creatinine levels. No exacerbation of accelerated nephrotoxic nephritis was observed in mice doubly deficient in factor B and C2, suggesting a protective role for C1q against renal inflammation that is proximal to C2 activation. There were increased murine IgG deposits, neutrophil numbers, and apoptotic cells in the glomeruli of C1q-deficient mice compared with wild-type mice. Renal expression of genes encoding procoagulant proteins was also enhanced in C1q-deficient mice. The increased IgG deposits and apoptotic cells in the glomeruli of C1q-deficient mice suggest that the exacerbation of disease may be due to a defect in the clearance of immune complexes and/or apoptotic cells from their kidneys.

Depletion of CD4(+) T cells aggravates glomerular and interstitial injury in murine adriamycin nephropathy

BACKGROUND

CD4(+) T cells play an important role in various types of immunologic renal disease, including lupus nephritis, IgA nephropathy, and crescentic glomerulonephritis. CD4(+) T cells are also major infiltrating lymphocytes in chronic tubulointerstitial inflammation associated with nonimmunological renal diseases. We suspected that CD4(+) T cells might contribute to disease progression and loss of renal function in chronic proteinuric renal disease (CPRD). To investigate this possibility, the effect of monoclonal antibody against CD4(+) lymphocytes (anti-CD4) was studied in a murine model (adriamycin nephropathy) of CPRD.

METHODS

Adriamycin nephropathy was produced in male BALB/c mice by a single intravenous injection of adriamycin (11 mg/kg). Anti-CD4 was given by intraperitoneal injection following the development of proteinuria at days 5, 6, 7, 21, and 37 after adriamycin. After six weeks, renal function and histology were studied by histomorphometry, immunohistochemistry, and flow cytometry.

RESULTS

Flow cytometric analysis showed a marked decrease in the number of CD4(+) T cells in blood and spleen of the antibody-treated animals (N = 7, P < 0.01). Adriamycin plus CD4(+) depletion mice had significantly greater mesangial expansion, glomerular sclerosis, and interstitial expansion than the mice on adriamycin alone. Interstitial infiltration with macrophages and CD8(+) cells was significantly increased in adriamycin plus CD4(+) depletion mice. Creatinine clearance (17.5 +/- 0.54 vs. 29.2 +/- 0.89 microL/min, P < 0.001) was significantly worse in the adriamycin plus CD4(+) depletion mice than in adriamycin alone mice and correlated with histologic change in glomeruli and interstitium.

CONCLUSIONS

Depletion of CD4(+) T cells promotes glomerular and interstitial injury in mice with established adriamycin nephropathy. These findings suggest that CD4(+) T cells have a protective role against the progression of adriamycin nephropathy.

Transtracheal administration of interleukin-12 induces neutrophil responses in the murine lung

Although the roles of interleukin-12 (IL-12) in the immunomodulation of antigen-specific responses are well characterized, the effects of IL-12 on the respiratory tract following mucosal administration are not well defined. Therefore, we investigated changes in the murine lung shortly after intranasal (i.n.) administration of murine IL-12. We showed that IL-12 induced neutrophil influx to the murine lung in both C57BL/6 and BALB/c mice. Histologic examination revealed that intranasal administration of IL-12 with liposomes induced focal neutrophil infiltration into the alveoli and a significant increase in neutrophils in bronchoalveolar lavage fluids when compared with administration of liposomes alone. In vitro chemotaxis assays indicated that the observed pulmonary neutrophil response induced by IL-12 could have been due in part to the direct chemotactic activity of IL-12 for murine neutrophils.

Chemokines, chemokine receptors, and renal disease: from basic science to pathophysiologic and therapeutic studies

Leukocyte trafficking from peripheral blood into affected tissues is an essential component of the inflammatory reaction to virtually all forms of injury and is an important factor in the development of many kidney diseases. Advances in the past few years have highlighted the central role of a family of chemotactic cytokines called chemokines in this process. Chemokines help to control the selective migration and activation of inflammatory cells into injured renal tissue. Chemokines and their receptors are expressed by intrinsic renal cells as well as by infiltrating cells during renal inflammation. This study summarizes the in vitro and in vivo data on chemokines and chemokine receptors in renal diseases with a special focus on potential therapeutic effects on inflammatory processes.

IFN-gamma mediates crescent formation and cell-mediated immune injury in murine glomerulonephritis

Features of crescentic glomerulonephritis suggest that it results from a T helper 1 (Th1) nephritogenic immune response. Interferon-gamma (IFN-gamma), produced by Th1 cells, is involved in T cell-directed macrophage activation in effector Th1 responses. The hypothesis that endogenous IFN-gamma contributes to the development of crescentic glomerulonephritis was tested by comparing the development of glomerulonephritis (induced by a planted antigen) and immune responses in normal C57BL/6 mice (IFN-gamma +/+) and in mice genetically deficient in IFN-gamma (IFN-gamma -/-). Ten days after the initiation of glomerulonephritis, IFN-gamma -/- mice developed fewer glomerular crescents (5+/-1% versus 26+/-3%, P<0.005), less severe glomerular injury, and less renal impairment. Effectors of delayed-type hypersensitivity (CD4+ T cells, macrophages, and fibrin) in glomeruli were reduced in IFN-gamma -/- mice. Skin delayed-type hypersensitivity to sheep globulin was reduced. Total antigen-specific Ig and splenocyte interleukin-2 production were unchanged, but antigen-specific serum IgG2a was reduced. Markers of an antigen-specific Th2 response (serum IgG1, splenocyte interleukin-4) were unchanged. Studies 22 d after the initiation of glomerulonephritis showed that IFN-gamma -/- mice still had fewer crescents (11+/-2% versus 22+/-3%, P = 0.02) and glomerular CD4+ T cells and macrophages than IFN-gamma +/+ mice. These studies demonstrate that endogenous IFN-gamma mediates crescentic glomerulonephritis by promoting cell-mediated immune injury. They support the hypothesis that crescentic glomerulonephritis is a manifestation of a Th1 nephritogenic immune response.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

IL-12 directs severe renal injury, crescent formation and Th1 responses in murine glomerulonephritis

Glomerular crescent formation characterizes severe glomerulonephritis (GN). Evidence suggests that crescent formation results from a delayed-type hypersensitivity-like Th1 response. As IL-12 directs Th1 responses, we tested the hypothesis that IL-12 is important in crescentic GN. Neutralization of IL-12 attenuated crescent formation and cell-mediated injury in C57BL/6 mice sensitized to and challenged with sheep anti-mouse glomerular basement membrane (GBM) globulin. Recombinant IL-12 induced severe crescentic GN with enhanced Th1 responses in C57BL/6 mice in which non-crescentic GN was induced by injecting anti-GBM globulin into naive mice. BALB/c mice do not develop significant crescent formation in these models, due either to regulatory effects of IL-4, or to deficits in IL-12 production/responsiveness. Administering IL-12 to BALB/c mice with GN induced Th1 responses and crescent formation, whereas IL-4-deficient BALB/c mice did not develop cell-mediated crescentic injury when GN was induced in sensitized mice. These results establish a central role for IL-12 in severe crescentic GN.