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Although in vitro observations indicate that long noncoding RNAs (lncRNAs) regulate innate immune responses, their effect upon immune tolerance in vivo has not been defined. We have identified a novel gene of unknown function for which sequence variation is associated with autoimmune diabetes in the nonobese diabetic (NOD) mouse strain. Bioinformatics and expression analyses indicate this gene encodes a lncRNA that is induced by Toll-like receptor (TLR) activation, localises to the nucleus and cytoplasm of dendritic cells, and binds to proteins within these cellular compartments. Moreover, sequence variation for this gene is associated with altered TLR-mediated cytokine production. Hence this gene was named Apics for Attenuator of Pattern recognition receptor-Induced Cytokine Secretion. To further investigate the function of this lncRNA, we established a C57BL/6 (B6) knockout mouse strain for Apics and discovered that Apics -deficient dendritic cells exhibit enhanced TLR-mediated cytokine production. Apics -deficient B6 mice also exhibit increased susceptibility to autoimmunity in two disease models: experimental autoimmune encephalomyelitis and experimental anti-neutrophil cytoplasmic antibody-associated vasculitis. Our study suggests that lncRNAs, such as Apics , can serve as TLR-inducible repressors that regulate the magnitude of innate immune responses to reduce the risk for developing autoimmune disease.

Although in vitro observations indicate that long noncoding RNAs (lncRNAs) regulate innate immune responses, their effect upon immune tolerance in vivo has not been defined. We have identified a novel gene of unknown function for which sequence variation is associated with autoimmune diabetes in the nonobese diabetic (NOD) mouse strain. Bioinformatics and expression analyses indicate this gene encodes a lncRNA that is induced by Toll-like receptor (TLR) activation, localizes to the nucleus and cytoplasm of dendritic cells, and binds to proteins within these cellular compartments. Moreover, sequence variation for this gene is associated with altered TLR-mediated cytokine production. Hence this gene was named Apics for Attenuator of Pattern recognition receptor-Induced Cytokine Secretion. To further investigate the function of this lncRNA, we established a C57BL/6 (B6) knockout mouse strain for Apics and discovered that Apics-deficient dendritic cells exhibit enhanced TLR-mediated cytokine production. Apics-deficient B6 mice also exhibit increased susceptibility to autoimmunity in two disease models: experimental autoimmune encephalomyelitis and experimental anti-neutrophil cytoplasmic antibody-associated vasculitis. Our study suggests that lncRNAs, such as Apics, can serve as TLR-inducible repressors that regulate the magnitude of innate immune responses to reduce the risk for developing autoimmune disease.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis involves innate and adaptive immune cells in the induction of autoimmunity and in autoimmune effector responses. Most Fcγ receptors (FcγRs) activate immune cells, but FcγRIIB, found in humans and mice on B cells and innate cells, is an inhibitory receptor. These studies tested the hypothesis that endogenous FcγRIIB negatively regulates autoreactivity and effector responses in experimental anti-myeloperoxidase (MPO) glomerulonephritis, using wild type and FcγRIIB-/- mice. After MPO immunization, FcγRIIB-/- mice developed higher MPO-ANCA titers and increased anti-MPO T cell responses. Transfer of FcγRIIB deficient dendritic cells loaded with a nephritogenic MPO peptide (MPO409-428) into wild type mice induced stronger autoimmunity than dendritic cells derived from wild type mice. Transferring anti-MPO antibodies into LPS primed mice resulted in increased glomerular neutrophil accumulation and injury in FcγRIIB-/- mice, showing a role for FcγRIIB in suppressing neutrophil activation. Inducing active autoimmunity to MPO followed by triggering T cell mediated glomerular injury by transfer of subnephritogenic doses of LPS and anti-MPO antibodies resulted in more disease in FcγRIIB-/- mice. Therefore endogenous FcγRIIB negatively regulates anti-MPO autoimmunity and glomerulonephritis via dendritic cells, B cells and neutrophils to limit MPO-ANCA production, T cell responses and neutrophil activation.

IL-17A is increased in serum and in kidney biopsies from patients with lupus nephritis, but direct evidence of pathogenicity is less well established. These studies sought to define the role of IL-17A in experimental lupus induced by the administration of pristane to WT and IL-17A-/- mice. Local and systemic immune responses were assessed after 6 days and 8 weeks, and autoimmunity, glomerular inflammation and renal injury were determined at 7 months. Peritoneal IL-17A production increased significantly 6 days after pristane injection, with innate cells (neutrophils and macrophages) being the predominant source of IL-17A. After 8 weeks, while systemic IL-17A was still readily detected in WT mice, IFN-γ and TNF were diminished in IL-17A-/- mice. Seven months after pristane, humoral autoimmunity was diminished in IL-17A-/- mice, with decreased serum lgG and anti-dsDNA antibody titers. Renal inflammation and injury was less in the absence of IL-17A. Compared to WT mice, glomerular IgG, complement deposition, glomerular CD4+ T cells and intrarenal pro-inflammatory mediator expression were decreased in IL-17A-/- mice. WT mice developed progressive albuminuria, but albuminuria (7 months: WT 271±56, IL-17A 88±16μg/day; P

Interleukin-12 (IL-12) directs the cognate nephritogenic T helper type 1 responses that initiate renal injury in murine crescentic glomerulonephritis (GN). The recent demonstration of IL-12 production by intrinsic renal cells, including mesangial and proximal tubular cells, raises the possibility that IL-12 from nonimmune cells may contribute to inflammatory renal injury. To address this possibility, the development of sheep anti-mouse glomerular basement membrane globulin-induced crescentic GN was studied in C57BL/6 wild-type (WT), IL-12-deficient (IL-12 -/-), and IL-12 "chimeric" mice. IL-12 chimeric mice were produced by transplantation of WT bone marrow into IL-12 -/- mice to restore IL-12 production by immune cells, while leaving them deficient in renal IL-12 production. WT and "sham" chimeric mice (normal bone marrow transplanted into WT mice) developed crescentic GN with glomerular T-cell and macrophage recruitment and impaired renal function (elevated proteinuria and serum creatinine) 10 d after initiation of GN. IL-12 -/- mice showed significant protection from GN. Chimeric IL-12 mice showed significant attenuation of crescent formation, glomerular T-cell and macrophage accumulation, and renal impairment, compared with WT and sham chimeric mice, but were not protected to the same extent as IL-12 -/- mice. IL-12 chimeric mice showed no attenuation of their systemic cognate immune response to the nephritogenic antigen (sheep globulin), indicated by antigen-specific circulating antibody and cutaneous delayed-type hypersensitivity. These studies indicate that IL-12 produced by non-bone marrow derived intrinsic renal cells contributes to immune renal injury. They provide the first in vivo demonstration of a proinflammatory role for an intrinsic renal cell-derived cytokine in renal inflammation.

The ability of interleukin-10 (IL-10) to inhibit macrophage recruitment, activation, and proliferation in vivo was studied in a macrophage-mediated, but T cell-independent, passive anti-glomerular basement membrane antibody-induced model of glomerulonephritis (GN) in rats. Treatment with recombinant murine IL-10 resulted in dose-dependent reductions in proteinuria (high dose: 16 +/- 1 mg/24 h; low dose: 30 +/- 2 mg/24 h; control treatment: 69 +/- 6 mg/24 h; normal: 7 +/- 1 mg/24 h) and glomerular macrophage recruitment (high dose: 1.8 +/- 0.1 macrophages per glomerular cross section [c/gcs]; low dose: 5.5 +/- 0.2 c/gcs; control treatment: 12.1 +/- 0.6 c/gcs). Macrophage and intrinsic glomerular cell proliferation were reduced at both doses of IL-10, as was glomerular expression of P-selectin and monocyte chemoattractant protein-1. IL-10 treatment also resulted in a dose-dependent reduction of macrophage activation as indicated by MHC class II and IL-1beta expression. Glomerular nitrite production by isolated cultured glomeruli was reduced after IL-10 treatment in vivo (high dose: 2.3 +/- 2.3 nmol/10(4) glomeruli per 72 h; low dose: 28 +/- 5 nmol/10(4) glomeruli per 72 h; control treatment: 82 +/- 11 nmol/10(4) glomeruli per 72 h). Tumor necrosis factor-alpha production was abolished by high-dose treatment and reduced by the lower dose (3.8 +/- 3.8 pg/10(4) glomeruli per 72 h; control treatment: 249 +/- 23 pg/10(4) glomeruli per 72 h). These studies demonstrate that IL-10 directly attenuates glomerular macrophage recruitment, activation, and proliferation in vivo and can significantly attenuate macrophage-mediated GN independent of any effects on T cells.

Minimal-change disease (MCD) and primary FSGS are important causes of idiopathic nephrotic syndrome (INS) and, in the case of FSGS, end-stage renal failure. Intriguing features of these diseases include their frequent response to steroids, their association with immune abnormalities, the existence

Human anti-glomerular basement membrane (GBM) disease has strong associations with HLA DRB1*1501. The target autoantigen is the non-collagenous domain of the α3 chain of Type IV collagen, α3(IV)NC1. T cell epitopes of α3(IV)NC1 were identified by immunizing mouse MHC-/-, HLA DRB1*1501 transgenic (1501tg) mice with overlapping 20mers. They defined a HLA DRB1*1501 restricted epitope (aa128-147) not reactive in HLA DRB1*0101 transgenic (0101tg) or C57BL/6 mice. 1501tg mice were immunized with α1(IV)NC1, α3(IV)NC1 or α1/α3 chimeric molecules, made by inserting the α3 aa17-31 (C2) or aa127-141 (C6) into the non-immunogenic α1 backbone. 1501tg mice immunized with α3(IV)NC1 or C6 responded to aa128-147 but not to aa8-27, but α1(IV)NC1 or C2-immunized mice did not respond to either peptide. CD4+ T cell clones, made from 1501tg mice and transferred into naive 1501tg mice, induced disease with necrotizing and crescentic glomeruli, albuminuria and renal failure, and glomerular CD4+ T cell and macrophage infiltrates. To determine if immunization with the restricted epitope causes disease, 1501tg or 0101tg mice were crossed with FcγRIIB-/- mice (Fcγ receptors are implicated in disease susceptibility). Immunization with either whole α3(IV)NC1 or the identified restricted epitope induced glomerulonephritis in 1501tg.FcγRIIB-/- mice but not in 0101tg.FcγRIIB-/- mice. These studies demonstrate that T cell responses in anti-GBM disease are defined by a HLA DRB1*1501 restricted T cell epitope.

Microscopic polyangiitis, characterized by pathogenic autoantibodies to neutrophil cytoplasmic proteins (ANCA), including myeloperoxidase (MPO), frequently targets the glomerulus. Although the pathogenicity of ANCA has been established, the role of CD4+ cells, cell mediated effector responses and MPO T cell epitopes are not known. By screening overlapping peptides of 20aa spanning the entire MPO molecule, we identified an immunodominant MPO CD4+ cell epitope (MPO409-428). Immunization with MPO409-428 induced disease similar to that seen with whole MPO when disease was triggered with anti-glomerular basement membrane antibodies. A CD4+ MPO409-428 specific clone transferred into Rag1-/- mice induced necrotizing glomerulonephritis with renal impairment when MPO409-428 was planted in glomeruli, or when whole MPO was deposited in glomeruli after neutrophil recruitment induced by transfer of anti-MPO antibodies with LPS. MPO409-428 also induced biologically active anti-MPO antibodies in mice. The MPO409-428 T cell epitope has a minimum immunogenic core region of 11 aa, MPO415-426, with several critical residues. These studies identify an immunodominant MPO T cell epitope and redefine how effector responses induce injury in MPO-ANCA associated microscopic polyangiitis. ANCA activate neutrophils not only induce injury, but also lodge the autoantigen MPO in glomeruli, where autoreactive CD4+ cells act to induce delayed-type hypersensitivity like necrotizing glomerular lesions.

In acute kidney injury, which is a significant cause of morbidity and mortality, cytokines and leukocytes promote inflammation and injury. We examined the pathogenic role of IL-17A in cisplatin-induced acute kidney injury. Intrarenal IL-17A mRNA transcription and protein expression were increased in wild-type mice after cisplatin-induced renal injury. An important role for IL-17A in the nephrotoxicity of cisplatin was demonstrated by observing protection from cisplatin-induced functional and histological renal injury in Il17a(-/-) and Rorγt(-/-) mice, as well as in mice treated pre-emptively with anti-IL-17A antibodies. Both renal injury and renal IL-1β and IL-17A production were attenuated in Asc(-/-) and Tlr2(-/-) mice, suggesting that cisplatin induces endogenous TLR2 ligand production and activates the ASC-dependent inflammasome complex, resulting in IL-1β and injurious IL-17A production. Neutrophils and natural killer cells are the likely targets of these pathways, because combined depletion of these cells was strongly protective; anti-IL-17A antibodies had no additional effect in this setting. Although IL-17A can also be produced by CD4(+) and γδ T cells, IL-17A from those cells does not contribute to renal injury. Cisplatin-induced injury was unchanged in γδ T-cell-deficient mice, whereas Il17a(-/-) CD4(+) T cells induced similar injury as did wild-type CD4(+) T cells on transfer to cisplatin-injected Rag1(-/-) mice. These studies demonstrate an important role for TLR2, the ASC inflammasome, and IL-17A in innate leukocytes in cisplatin-induced renal injury.

Th1 and Th2T 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.

Foxp3(+) T-regulatory cells (Tregs) may suppress pathogenic inflammation; however, although transferred Tregs lessen glomerulonephritis in mice, the role of endogenous foxp3(+) cells is not known. To study this, we characterized endogenous foxp3(+) cells in accelerated anti-glomerular basement membrane (GBM) nephritis by using foxp3(GFP) reporter mice to track their responses in early and established disease. Further, diphtheria toxin was used to ablate foxp3(+) Tregs in foxp3(DTR) mice after establishing an immune response. In this model, mice were immunized with sheep globulin in adjuvant, and sheep anti-mouse GBM globulin was injected after 4 days to initiate progressive histological and functional injury. Intrarenal leukocytic infiltrates were increased by day 3 but intrarenal foxp3(+) Tregs, present in interstitial and periglomerular areas, were only increased at day 7. Ablation of foxp3(+) Tregs after injection of anti-GBM globulin increased renal injury and systemic T-cell responses, including increased interferon-γ and interleukin-17A (IL-17A) production, but no change in antibody titers. Compared with foxp3(+) Tregs isolated from naive mice, those from immunized mice produced more IL-10 and more effectively regulated CD4(+)foxp3(-) responder T cells. Thus, endogenous foxp3(+) Tregs infiltrate the kidney in glomerulonephritis, and deleting foxp3(+) cells after the induction of immune responses upregulated T-cell reactions and enhanced disease. Hence, endogenous foxp3(+) cells have increased suppressive capacity after immune stimuli.

Crescentic glomerulonephritis (GN) results from IL-12-driven Th1-directed cell-mediated responses (akin to delayed-type hypersensitivity (DTH)) directed against glomerular Ags. CD40-CD154 interactions are critical for IL-12 production and Th1 polarization of immune responses. Crescentic anti-glomerular basement membrane GN was induced in C57BL/6 (wild-type (WT)) mice (sensitized to sheep globulin) by planting this Ag (as sheep anti-mouse glomerular basement membrane globulin) in their glomeruli. Crescentic GN did not develop in CD40−/− mice due to significantly reduced nephritogenic Th1 responses. IL-12 was administered to CD40−/− mice with GN to dissect interactions between IL-12 and CD40 in inducing nephritogenic immunity and injury. Administration of IL-12 to CD40−/− mice restored Th cell IFN-γ production, and up-regulated intrarenal chemokines and glomerular T cell and macrophage accumulation compared with WT control mice. Despite this, renal macrophages were not activated and renal injury and dermal DTH were not restored. Thus, CD40-directed IL-12 drives Th1 generation and effector cell recruitment but CD40 is required for activation. To test this hypothesis, activated OT-II OVA-specific CD4+ cells and OVA323–339-loaded nonresponsive APCs were transferred into footpads of WT, CD40−/−, and macrophage-depleted WT mice. WT mice developed significant DTH compared with CD40−/− and macrophage-depleted WT mice. This study demonstrated that CD40-induced IL-12 is required for generation of systemic Th1 immunity to nephritogenic Ags, and that IL-12 enhances Th1 effector cell recruitment to peripheral sites of Ag presentation via generation of local chemokines. Effector cell activation, renal DTH-like injury, and dermal DTH require direct Th1 CD154/macrophage CD40 interactions.

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 β2 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.

Goodpasture's disease, an "organ-specific" autoimmune disease is manifest by rapidly progressive glomerulonephritis and pulmonary hemorrhage. Studies into the pathogenesis of this disease have shed light on the autoantigen (the non-collagenous domain of the alpha3 chain of type IV collagen, alpha3(IV)NC1) and its epitopes, as well as the involvement of autoantibodies and cellular effectors in disease. The discovery of alpha3(IV)NC1 lead to studies that defined the structure and biology of type IV collagen and are defining B and T cell epitopes. Goodpasture autoantibody epitopes are "cryptic" in that they are structurally sequestered by adjacent non-collagenous domains of alpha4 and alpha5 type IV collagen. T cell epitope studies in rats demonstrated that a 13-mer could induce experimental autoimmune glomerulonephritis. T cells from patients with Goodpasture's recognize two epitopes, in regions which are highly susceptible in antigen processing by endosomal proteases. Goodpasture's disease is strongly associated with HLA DRB1 genes, whereby DRB1*1501 confers susceptibility and the DRB1*0701 and DRB1*0101 are dominantly protective. Experimental data implicate both autoantibodies and cell mediated immunity as disease effectors. Observations in humans suggest that regulatory T cells are associated with the development of self-immunoregulation in the convalescent phase of disease.

Systemic lupus erythematosus (SLE) is a serious systemic autoimmune disease of unknown etiology. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is operative in innate and adaptive immunity and important in immune-mediated diseases such as rheumatoid arthritis and atherosclerosis. The functional relevance of MIF in systemic autoimmune diseases such as SLE is unknown. Using the lupus-prone MRL/lpr mice, we aim to examine the expression and function of MIF in this murine model of systemic autoimmune disease. These experiments revealed that renal MIF expression was significantly higher in MRL/lpr mice compared with nondiseased control mice (MRL/MpJ), and MIF was also markedly up-regulated in skin lesions of MRL/lpr mice. To examine the effect of MIF on development of systemic autoimmune disease, we generated MRL/lpr mice with a targeted disruption of the MIF gene (MIF−/−MRL/lpr), and compared their disease manifestations to MIF+/+MRL/lpr littermates. MIF−/−MRL/lpr mice exhibited significantly prolonged survival, and reduced renal and skin manifestations of SLE. These effects occurred in the absence of major changes in T and B cell markers or alterations in autoantibody production. In contrast, renal macrophage recruitment and glomerular injury were significantly reduced in MIF−/−MRL/lpr mice, and this was associated with reduction in the monocyte chemokine MCP-1. Taken together, these data suggest MIF as a critical effector of organ injury in SLE.

A major dilemma facing patients with breast cancer is how to decide between over treating indolent tumors and failing to adequately treat aggressive, potentially lethal cancers. Determination of the metastatic potential of a patient's breast cancer would clearly help guide those treatment decisions. Breast cancer commonly spreads to bone in 70% of women with advanced disease. However, the mechanism of bone metastasis is not well understood. One possibility is that the microenvironment within bone marrow, highly rich in growth factors and cytokines, is suitable for the proliferation of breast cancer cells. In this study, we developed a method for implanting human bone in NOD/SCID mice and show that the human bone implants are viable for more than 20 weeks. This human bone NOD/SCID mouse model provides an opportunity to functionally characterize human breast cancer cell behavior in an in vivo human microenvironment. Several breast tumor cell lines have been shown to grow in the human-bone-NOD/SCID model system, however each line has a different functional profile. Here we show that cotransplantation of GFP-MDA-MB-231 breast cancer cells with morcellized human bone allows for tissue specific metastasis to an initially tumor free bone implant. Furthermore, metastasis of breast tumor cells to implanted tumor-free human bone was seen when patient bone containing a metastatic breast tumor was implanted in the host mouse. With this model, we can distinguish between primary invasive breast tumors with and without bone metastatic potential.

CD100 participates in adaptive immune responses and is important in neural cell migration. To determine the role of endogenous CD100 in severe glomerular inflammation, we induced experimental crescentic glomerulonephritis by planting a foreign antigen in glomeruli of sensitized normal and CD100-deficient (CD100(-/-)) mice. Fewer CD100(-/-) glomeruli exhibited crescent formation or severe histological changes. Antigen-specific immune responses were reduced in CD100(-/-) mice. There was less interferon (IFN)-gamma and interleukin (IL)-4 production by splenocytes and fewer activated T and B cells were present in lymph nodes of immunized CD100(-/-) mice. Serum antigen-specific immunoglobulin (IgG) levels were also decreased. Glomerular macrophage and CD4(+) cell infiltration, and IgG and C3 deposition were attenuated. Normal kidneys expressed mRNA for CD100 and plexin-B1 (the tissue receptor of CD100). Direct immunofluorescence showed that renal-CD100 protein was predominantly in tubules, while plexin-B1 was present in both glomeruli and tubules. To determine whether glomerular plexin-B1 mediates leucocyte recruitment via leucocyte CD100, recruitment was studied after passive transfer of heterologous antibody (attracting neutrophils) or isologous antibody (attracting macrophages). Glomerular macrophages were reduced in CD100(-/-) mice, but neutrophil recruitment was equivalent, consistent with CD100 expression on macrophages, but not neutrophils. CD100 promotes severe nephritogenic immune responses and leucocyte CD100-glomerular plexin-B1 interactions enhance macrophage recruitment to glomeruli.

The plasminogen-plasmin system has potential beneficial or deleterious effects in the context of renal fibrosis. Recent studies have implicated plasminogen activators or their inhibitors in this process.The development of renal interstitial fibrosis was studied in mice genetically deficient in plasminogen (plg-/- mice) and littermate controls (plg+/+ mice) by inducing unilateral ureteric obstruction (UUO) by ligating the left ureter.Collagen accumulation in the kidney was decreased in plg-/- mice at 21 days compared with plg+/+ mice by hydroxyproline assay (plg+/+ 19.0 +/- 1.2 microg collagen/mg tissue, plg-/- 15.6 +/- 0.5 microg collagen/mg tissue, P= 0.04). Macrophage accumulation in plg-/- mice was reduced at 21 days, consistent with a role for plasmin in macrophage recruitment in this model. Myofibroblast accumulation, assessed by the expression of alpha-smooth muscle actin (alpha-SMA), was similar in both groups at both time points. Endogenous plasmin played a role in the activation of transforming growth factor-beta (TGF-beta), as plg-/- mice had lower ratios of betaig-h3:TGF-beta1 mRNA than plg+/+ mice. Matrix metalloproteinase (MMP)-9 activity was unchanged in the absence of plasmin, but MMP-2 activity was decreased.Plasminogen, the key proenzyme in the plasminogen-plasmin system, does not protect mice from experimental interstitial fibrosis and may have significant pathogenetic effects. These findings, together with other recently published studies in the biology of renal fibrosis, imply that effects of proteins such as plasminogen activator inhibitor-1 (PAI-1), tissue-type plasminogen activator (tPA), and urokinase-type plasminogen activator receptor (uPAR) on renal fibrosis occur independently from the generation of plasmin.

Anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is a rare and severe autoimmune multisystemic disease. Its pathogenesis involves multiple arms of the immune system, as well as complex interactions between immune cells and target organs. Experimental animal models of disease can provide the crucial link from human disease to translational research into new therapies. This is particularly true in AAV, due to low disease incidence and substantial disease heterogeneity. Animal models allow for controlled environments in which disease mechanisms can be defined, without the clinical confounders of environmental and lifestyle factors. To date, multiple animal models have been developed, each of which shed light on different disease pathways. Results from animal studies of AAV have played a crucial role in enhancing our understanding of disease mechanisms, and have provided direction toward newer targeted therapies. This review will summarize our understanding of AAV pathogenesis as has been gleaned from currently available animal models, as well as address their strengths and limitations. We will also discuss the potential for current and new animal models to further our understanding of this important condition.