CD103 Regulates Dermal Regulatory T Cell Motility and Interactions with CD11c-Expressing Leukocytes to Control Skin Inflammation

Dermal regulatory T cells (Tregs) are essential for maintenance of skin homeostasis and control of skin inflammatory responses. In mice, Tregs in the skin are characterized by high expression of CD103, the αE integrin. Evidence indicates that CD103 promotes Treg retention within the skin, although the mechanism underlying this effect is unknown. The main ligand of CD103, E-cadherin, is predominantly expressed by cells in the epidermis. However, because Tregs are predominantly located within the dermis, the nature of the interactions between E-cadherin and CD103-expressing Tregs is unclear. In this study, we used multiphoton intravital microscopy to examine the contribution of CD103 to Treg behavior in resting and inflamed skin of mice undergoing oxazolone-induced contact hypersensitivity. Inhibition of CD103 in uninflamed skin did not alter Treg behavior, whereas 48 h after inducing contact hypersensitivity by oxazolone challenge, CD103 inhibition increased Treg migration. This coincided with E-cadherin upregulation on infiltrating myeloid leukocytes in the dermis. Using CD11c-enhanced yellow fluorescent protein (EYFP) × Foxp3-GFP dual-reporter mice, inhibition of CD103 was found to reduce Treg interactions with dermal dendritic cells. CD103 inhibition also resulted in increased recruitment of effector CD4+ T cells and IFN-γ expression in challenged skin and resulted in reduced glucocorticoid-induced TNFR-related protein expression on Tregs. These results demonstrate that CD103 controls intradermal Treg migration, but only at later stages in the inflammatory response, when E-cadherin expression in the dermis is increased, and provide evidence that CD103-mediated interactions between Tregs and dermal dendritic cells support regulation of skin inflammation.

Equity and diversity in the nephrology workforce in Australia and New Zealand

BACKGROUND

Despite diversity initiatives, inequities persist in medicine with negative implications for the workforce and patients. Little is known about workplace inequity in nephrology.

AIM

To describe perceptions and experiences of bias by health professionals in the Australian and New Zealand Society of Nephrology (ANZSN), focussing on gender and race.

METHODS

A web-based survey of ANZSN members recorded degree of perceived inequity on a Likert scale, ranging from 1 (none) to 5 (complete). Groups were compared using Mann-Whitney U-test and logistic regression. Comments were synthesised using qualitative methods to explore themes of inequity and pathways to an inclusive future.

RESULTS

Of the 620 members of the ANZSN, there were 134 (22%) respondents, of whom 57% were women and 67% were White. The majority (88%) perceived inequities in the workforce. Perceived drivers of inequity were gender (84/113; 75%), carer responsibilities (74/113; 65%) and race (64/113; 56%). Half (74/131) had personally experienced inequity, based on gender in 70% (52/74) and race in 39% (29/75) with perceived discrimination coming from doctors, patients, academics and health administrators. White males were least likely (odds ratio 0.39; 95% confidence interval 0.18-0.90) to experience inequity. Dominant themes from qualitative analysis indicated that the major impacts of inequity were limited opportunities for advancement and lack of formal assistance for those experiencing inequities. Proposed solutions to reduce inequity included normalising the discourse on inequity at an organisational level, with policy changes to ensure diverse representation on committees and in executive leadership positions.

CONCLUSIONS

Inequity, particularly driven by gender and race, is common for nephrology health professionals in Australia and New Zealand and impacts career progression.

Inhibition of NETosis by a Nuclear-Penetrating Anti-DNA Autoantibody

Nuclear-penetrating anti-DNA autoantibodies have therapeutic potential as delivery agents and in targeting DNA and the DNA damage response (DDR). Derivatives of such Abs have advanced to human testing in genetic disease and are in preparation for oncology clinical trials. DNA release associated with neutrophil extracellular traps (NETs) contributes to immunity, inflammation, and the pathophysiology of multiple diseases. The DDR contributes to mechanisms of NETosis, and we hypothesize that anti-DNA autoantibodies that localize into live cell nuclei and inhibit DNA repair will suppress release of NETs by activated neutrophils. In the current study we evaluated the impact of a nuclear-penetrating anti-DNA autoantibody that interferes with the DDR on decondensation and release of DNA and NETs by activated human granulocyte-like differentiated PLB-985 cells and neutrophils isolated from C57BL/6 mice. The response of cells pretreated with control or autoantibody to subsequent stimulators of NETosis, including PMA and the calcium ionophore ionomycin, was evaluated by DAPI and SYTOX Green stains, measurement of DNA release, analysis of histone citrullination by Western blot, or visualization of NETs by immunostaining and confocal fluorescence microscopy. Autoantibody treatment of the cells yielded significant inhibition of NADPH oxidase-dependent and independent NETosis. These findings establish the concept of nuclear-penetrating anti-DNA autoantibodies as modulators of neutrophil biology with potential for use in strategies to suppress NETosis.

Sex-Based Differences in Risk Factors and Complications of Chronic Kidney Disease

Globally, females are ∼30% more likely to have pre-dialysis chronic kidney disease (CKD) than males for reasons that are not fully understood. CKD is associated with numerous adverse health outcomes which makes understanding and working to eradicating sex based disparities in CKD prevalence essential. This review maps both what is known, and what is unknown, about the way sex and gender impacts (1) the epidemiology and risk factors for CKD including age, diabetes, hypertension, obesity, smoking, and cerebrovascular disease, and (2) the complications from CKD including kidney disease progression, cardiovascular disease, CKD mineral and bone disorders, anaemia, quality-of-life, cancer and mortality. This mapping can be used to guide future research.

Neutrophil Extracellular Traps: A Potential Therapeutic Target in MPO-ANCA Associated Vasculitis?

Our understanding of immune recognition and response to infection and non-infectious forms of cell damage and death is rapidly increasing. The major focus is on host immunity and microbiological invasion. However, it is also clear that these same pathways are important in the initiation and maintenance of autoimmunity and the damage caused to targeted organs. Understanding the involvement of cell death in autoimmune disease is likely to help define critical pathways in the immunopathogenesis of autoimmune disease and new therapeutic targets. An important immune responder cell population in host defense and autoimmunity is the neutrophil. One autoimmune disease where neutrophils play important roles is MPO-ANCA Microscopic Vasculitis. This a severe disease that results from inflammation to small blood vessels in the kidney, the glomeruli (high blood flow and pressure filters). One of the best studied ways in which neutrophils participate in this disease is by cell death through NETosis resulting in the discharge of proinflammatory enzymes and nuclear fragments. In host defense against infection this process helps neutralize pathogens however in auto immunity NETosis results in injury and death to the surrounding healthy tissues. The major autoimmune target in this disease is myeloperoxidase (MPO) which is found uniquely in the cytoplasm of neutrophils. Although the kidney is the major organ targeted in this disease MPO is not expressed in the kidney. Autoantibodies target surface MPO on activated circulating neutrophils resulting in their lodgment in glomerular capillaries where they NETose releasing extracellularly MPO and nuclear fragments initiating injury and planting the key autoantigen MPO. It is the cell death of neutrophils that changes the kidney from innocent bystander to major autoimmune target. Defining the immunopathogenesis of this autoimmune disease and recognizing critical injurious pathways will allow therapeutic intervention to block these pathways and attenuate autoimmune injury. The insights (regarding mechanisms of injury and potential therapeutic targets) are likely to be highly relevant to many other autoimmune diseases.

Biologicals targeting T helper cell subset differentiating cytokines are effective in the treatment of murine anti-myeloperoxidase glomerulonephritis

Anti-myeloperoxidase nephritogenic autoimmunity induces severe glomerulonephritis. To assess the therapeutic potential of monoclonal antibodies targeting T helper (Th) subset differentiation determining cytokines, we studied a murine model of anti-myeloperoxidase glomerulonephritis. The temporal participation of T helper subsets was determined by quantitating gene expression of CD4⁺ T-cells isolated from nephritic kidneys and cytokine production by lymphocytes from nodes draining myeloperoxidase immunization sites. Th17 cytokines (IL-17A and IL-6) rose rapidly but declined as autoimmunity matured when Th1 cytokines (IL-12 and TNF) predominated. Therefore, T helper subset participation in anti-myeloperoxidase autoimmunity is biphasic, with Th17 early and Th1 late. To confirm the functional relevance of this biphasic pattern, we compared systemic anti-myeloperoxidase autoimmunity in wild type, Th17 deficient and Th1 deficient mice. Early, Th1 deficient mice developed similar autoimmunity and glomerulonephritis to wild type mice. However, Th17 deficient mice had significantly reduced anti-myeloperoxidase autoimmunity. In late autoimmunity, Th1 deficient mice developed reduced autoimmunity and were protected from anti-myeloperoxidase glomerulonephritis. The therapeutic potential of these findings were demonstrated by neutralizing monoclonal antibodies. Targeting IL-23p19 attenuated early Th17 dominated anti-myeloperoxidase autoimmunity and glomerulonephritis but not late phase disease. Targeting IL-12p35 attenuated late phase Th1 dominated anti-myeloperoxidase autoimmunity and glomerulonephritis but not early autoimmunity or glomerulonephritis. Targeting both T helper subsets with an anti-IL-12p40 monoclonal antibody was effective during both early and late phases of anti-myeloperoxidase glomerulonephritis. Thus, definition of dominant T helper differentiating subsets in anti-myeloperoxidase glomerulonephritis by renal CD4⁺ T-cell cytokine gene expression allows effective proper phase monoclonal antibody treatment of anti-myeloperoxidase glomerulonephritis.

Intrarenal Toll-like receptor 4 and Toll-like receptor 2 expression correlates with injury in antineutrophil cytoplasmic antibody-associated vasculitis

In antineutrophil cytoplasmic antibody-associated vasculitis (AAV), Toll-like receptors (TLRs) may be engaged by infection-associated patterns and by endogenous danger signals, linking infection and innate inflammation with this autoimmune disease. This study examined intrarenal TLR2, TLR4, and TLR9 expression and renal injury in AAV, testing the hypothesis that increased TLR expression correlates with renal injury. Patients with AAV exhibited both glomerular and tubulointerstitial expression of TLR2, TLR4, and TLR9, with TLR4 being the most prominent in both compartments. Glomerular TLR4 expression correlated with glomerular segmental necrosis and cellular crescents, with TLR2 expression correlating with glomerular segmental necrosis. The extent and intensity of glomerular and tubulointerstitial TLR4 expression and the intensity of glomerular TLR2 expression inversely correlated with the presenting estimated glomerular filtration rate. Although myeloid cells within the kidney expressed TLR2, TLR4, and TLR9, TLR2 and TLR4 colocalized with endothelial cells and podocytes, whereas TLR9 was expressed predominantly by podocytes. The functional relevance of intrarenal TLR expression was further supported by the colocalization of TLRs with their endogenous ligands high-mobility group box 1 and fibrinogen. Therefore, in AAV, the extent of intrarenal TLR4 and TLR2 expression and their correlation with renal injury indicates that TLR4, and to a lesser degree TLR2, may be potential therapeutic targets in this disease.

Visualizing Macrophage Extracellular Traps Using Confocal Microscopy

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal microscopy methods to visualize macrophage extracellular traps (METs). These extracellular traps are defined by the presence of extracellular chromatin with co-expression of other components such as granule proteases, citrullinated histones, and peptidyl arginase deiminase (PAD). The expression of METs is generally measured after exposure to a stimulus and compared to un-stimulated samples. Samples are also included for background and isotype control. Cells are analyzed using well-defined image analysis software. Confocal microscopy may be used to define the presence of METs both in vitro and in vivo in lung tissue.

Interleukin-17RA Promotes Humoral Responses and Glomerular Injury in Experimental Rapidly Progressive Glomerulonephritis

BACKGROUND/AIMS

Interleukin (IL)-17A and IL-17F are proinflammatory cytokines, which signal through a receptor complex consisting of IL-17RA and IL-17RC subunits. We sought to define the role of IL-17RA expression by leukocytes and stromal cells in nephritogenic immunity and injury in experimental glomerulonephritis.

METHODS

Glomerulonephritis was induced in wild-type and IL-17RA-deficient (IL-17RA-/-) mice by sheep anti-mouse glomerular basement membrane globulin. Renal injury and immune responses were assessed at day 21. Glomerulonephritis was induced in bone marrow (BM) chimeric mice, with either BM or tissue cell (TC) deficiency of IL-17RA. To assess humoral responses, WT and IL-17RA-/- mice were sensitized to sheep globulin and euthanized 10 days later.

RESULTS

IL-17RA-/- mice had reduced glomerular crescent formation, neutrophils and macrophages compared to wild-type mice, while nephritic BM-TC+ mice developed less glomerular segmental necrosis. IL-17RA expression was required in both BM and TC for maximal systemic interferon-γ expression. Antigen-specific humoral immune responses were impaired in the absence of IL-17RA. Compared to BM+TC+ mice, glomerular IgG and C3 deposition was reduced in BM+TC- and BM-TC+ mice, respectively. Humoral immunity was also impaired in BM- and TC-deficient chimeras. BM+TC- mice had fewer B cells expressing CXCR5, while IL-17RA-/- mice had abnormal germinal centre development after immunization, with reduced follicular B cell and follicular helper T-cell CXCR5 expression, explaining the impaired humoral immunity.

CONCLUSION

IL-17RA contributes to experimental glomerulonephritis, with IL-17RA expression on both leukocytes and stromal cells being required for the full expression of nephritogenic humoral immunity.

CD8+ T Cells Effect Glomerular Injury in Experimental Anti-Myeloperoxidase GN

Observations in patients with ANCA-associated vasculitis suggest that CD8⁺ T cells participate in disease, but there is no experimental functional evidence of pathologic involvement for these cells. Myeloperoxidase (MPO) is a well defined autoantigen in ANCA-associated vasculitis. Studies in experimental models of anti-MPO GN suggest that, after ANCA-induced neutrophil localization, deposited MPO within glomeruli is recognized by autoreactive T cells that contribute to injury. We tested the hypothesis that CD8⁺ T cells mediate disease in experimental ANCA-associated vasculitis. CD8⁺ T cell depletion in the effector phase of disease attenuated injury in murine anti-MPO GN. This protection associated with decreased levels of intrarenal IFN-γ, TNF, and inflammatory chemokines and fewer glomerular macrophages. Moreover, we identified a pathogenic CD8⁺ T cell MPO epitope (MPO_431-439) and found that cotransfer of MPO_431-439-specific CD8⁺ T cell clones exacerbated disease mediated by MPO-specific CD4⁺ cells in Rag1^-/- mice. Transfer of MPO_431-439-specific CD8⁺ cells without CD4⁺ cells mediated glomerular injury when MPO was planted in glomeruli. These results show a pathogenic role for MPO-specific CD8⁺ T cells, provide evidence that CD8⁺ cells are a therapeutic target in ANCA-associated vasculitis, and suggest that a molecular hotspot within the MPO molecule contains important CD8⁺, CD4⁺, and B cell epitopes.

Mast Cell Stabilization Ameliorates Autoimmune Anti-Myeloperoxidase Glomerulonephritis

Observations in experimental murine myeloperoxidase (MPO)-ANCA-associated vasculitis (AAV) show mast cells degranulate, thus enhancing injury as well as producing immunomodulatory IL-10. Here we report that, compared with biopsy specimens from control patients, renal biopsy specimens from 44 patients with acute AAV had more mast cells in the interstitium, which correlated with the severity of tubulointerstitial injury. Furthermore, most of the mast cells were degranulated and spindle-shaped in patients with acute AAV, indicating an activated phenotype. We hypothesized that the mast cell stabilizer disodium cromoglycate would attenuate mast cell degranulation without affecting IL-10 production. We induced anti-MPO GN by immunizing mice with MPO and a low dose of anti-glomerular basement membrane antibody. When administered before or after induction of MPO autoimmunity in these mice, disodium cromoglycate attenuated mast cell degranulation, development of autoimmunity, and development of GN, without diminishing IL-10 production. In contrast, administration of disodium cromoglycate to mast cell-deficient mice had no effect on the development of MPO autoimmunity or GN. MPO-specific CD4(+) effector T cell proliferation was enhanced by co-culture with mast cells, but in the presence of disodium cromoglycate, proliferation was inhibited and IL-10 production was enhanced. These results indicate that disodium cromoglycate blocks injurious mast cell degranulation specifically without affecting the immunomodulatory role of these cells. Thus as a therapeutic, disodium cromoglycate may substantially enhance the regulatory role of mast cells in MPO-AAV.

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.

Endogenous myeloperoxidase is a mediator of joint inflammation and damage in experimental arthritis

OBJECTIVE

Myeloperoxidase (MPO) is implicated as a local mediator of tissue damage when released extracellularly in many chronic inflammatory diseases. The purpose of this study was to explore the role of endogenous MPO in experimental rheumatoid arthritis (RA).

METHODS

K/BxN serum-transfer arthritis was induced in C57BL/6 wild-type (WT) and MPO knockout (MPO(-/-) ) mice, and disease development was assessed. MPO activity was measured in joint tissues from mice with or without K/BxN arthritis. Collagen-induced arthritis (CIA) was induced in WT and MPO(-/-) mice, and disease development and immune responses were examined. MPO expression was assessed in synovial biopsy samples from patients with active RA, and the effect of MPO on synovial fibroblasts was tested in vitro.

RESULTS

MPO was up-regulated in the joints of mice with K/BxN arthritis, and MPO deficiency attenuated the severity of the disease without affecting circulating cytokine levels. In CIA, MPO(-/-) mice had enhanced CD4+ T cell responses and reduced frequency of regulatory T cells in the lymph nodes and spleen, as well as augmented interleukin-17A and diminished interferon-γ secretion by collagen-stimulated splenocytes, without an effect on circulating anticollagen antibody levels. Despite enhanced adaptive immunity in secondary lymphoid organs, CIA development was attenuated in MPO(-/-) mice. Intracellular and extracellular MPO was detected in the synovium of patients with active RA, and human MPO enhanced the proliferation and decreased the apoptosis of synovial fibroblasts in vitro.

CONCLUSION

MPO contributes to the development of arthritis despite suppressing adaptive immunity in secondary lymphoid organs. This suggests distinct effects of local MPO on arthritogenic effector responses.

The HLA-DRB1*15:01-restricted Goodpasture's T cell epitope induces GN

Human anti-glomerular basement membrane (GBM) disease strongly associates with HLA-DRB1*15:01. The target autoantigen in this disease is the noncollagenous domain of the α3 chain of type IV collagen, α3(IV)NC1, but critical early T cell epitopes presented by this human MHC class II molecule are unknown. Here, by immunizing HLA-DRB1*15:01 transgenic mice with whole recombinant α3(IV)NC1 and with overlapping α3(IV)NC1 peptides, we defined a HLA-DRB1*15:01-restricted α3(IV)NC1 T cell epitope (α3136-146) with four critical residues. This peptide was not immunogenic in HLA-DRB1*01:01 transgenic or C57BL/6 mice. The T cell epitope is naturally processed from α3(IV)NC1. CD4(+) T cell clones, generated from HLA-DRB1*15:01 transgenic mice and specific for α3136-146, transferred disease into naive HLA-DRB1*15:01 transgenic mice, evidenced by the development of necrotizing crescentic GN, albuminuria, renal impairment, and accumulation of CD4(+) T cells and macrophages in glomeruli. Because Fcγ receptors are implicated in disease susceptibility, we crossed HLA transgenic mice onto an FcγRIIb-deficient background. Immunization with either α3136-146 or α3(IV)NC1 induced GN in HLA-DRB1*15:01 transgenic FcγRIIb-deficient mice, but HLA-DRB1*01:01 transgenic FcγRIIb-deficient mice were unaffected. Taken together, these results demonstrate that the HLA-DRB1*15:01-restricted T cell epitope α3136-146 can induce T cell responses and injury in anti-GBM GN.

Thymic deletion and regulatory T cells prevent antimyeloperoxidase GN

Loss of tolerance to neutrophil myeloperoxidase (MPO) underlies the development of ANCA-associated vasculitis and GN, but the mechanisms underlying this loss of tolerance are poorly understood. Here, we assessed the role of the thymus in deletion of autoreactive anti-MPO T cells and the importance of peripheral regulatory T cells in maintaining tolerance to MPO and protecting from GN. Thymic expression of MPO mRNA predominantly localized to medullary thymic epithelial cells. To assess the role of MPO in forming the T cell repertoire and the role of the autoimmune regulator Aire in thymic MPO expression, we compared the effects of immunizing Mpo(-/-) mice, Aire(-/-) mice, and control littermates with MPO. Immunized Mpo(-/-) and Aire(-/-) mice developed significantly more proinflammatory cytokine-producing anti-MPO T cells and higher ANCA titers than control mice. When we triggered GN with a subnephritogenic dose of anti-glomerular basement membrane antibody, Aire(-/-) mice had more severe renal disease than Aire(+/+) mice, consistent with a role for Aire-dependent central deletion in establishing tolerance to MPO. Furthermore, depleting peripheral regulatory T cells in wild-type mice also led to more anti-MPO T cells, higher ANCA titers, and more severe GN after immunization with MPO. Taken together, these results suggest that Aire-dependent central deletion and regulatory T cell-mediated peripheral tolerance both play major roles in establishing and maintaining tolerance to MPO, thereby protecting against the development of anti-MPO GN.

Mast cells contribute to peripheral tolerance and attenuate autoimmune vasculitis

Mast cells contribute to the modulation of the immune response, but their role in autoimmune renal disease is not well understood. Here, we induced autoimmunity resulting in focal necrotizing GN by immunizing wild-type or mast cell-deficient (Kit(W-sh/W-sh)) mice with myeloperoxidase. Mast cell-deficient mice exhibited more antimyeloperoxidase CD4+ T cells, enhanced dermal delayed-type hypersensitivity responses to myeloperoxidase, and more severe focal necrotizing GN. Furthermore, the lymph nodes draining the sites of immunization had fewer Tregs and reduced production of IL-10 in mice lacking mast cells. Reconstituting these mice with mast cells significantly increased the numbers of Tregs in the lymph nodes and attenuated both autoimmunity and severity of disease. After immunization with myeloperoxidase, mast cells migrated from the skin to the lymph nodes to contact Tregs. In an ex vivo assay, mast cells enhanced Treg suppression through IL-10. Reconstitution of mast cell-deficient mice with IL-10-deficient mast cells led to enhanced autoimmunity to myeloperoxidase and greater disease severity compared with reconstitution with IL-10-intact mast cells. Taken together, these studies establish a role for mast cells in mediating peripheral tolerance to myeloperoxidase, protecting them from the development of focal necrotizing GN in ANCA-associated vasculitis.

TLR9 and TLR4 are required for the development of autoimmunity and lupus nephritis in pristane nephropathy

Systemic lupus erythematosus is a common autoimmune disease, with kidney involvement a serious complication associated with poor prognosis. Humoral immune responses constitute the hallmark of disease, however T helper cells are required for the generation of autoantibodies, as well as the induction and progression of renal injury. Administration of pristane to genetically intact mice results in the development of hypergammaglobulinaemia with the production of lupus like autoantibodies and proliferative glomerulonephritis, with similarities to human lupus nephritis. TLRs are intricately linked to the development of autoimmunity and are involved in the development of lupus nephritis. We injected wild type, TLR9-/- and TLR4-/- mice with pristane and assessed cellular and humoral autoimmunity and renal injury, 8 months later. TLR9-/- mice demonstrated a predominant decrease in Th1 cytokine production which resulted in decreased anti-RNP antibody levels, while anti-dsDNA levels remained intact. Compared to wild type mice treated with pristane, functional and histological renal injury and glomerular immunoglobulin and complement deposition was decreased in TLR9-/- mice. TLR4-/- mice demonstrated a global decrease in both Th1, IFNγ, and Th17 associated IL-17A and IL-6 cytokine production. Autoantibody levels of anti-dsDNA and anti-RNP were both decreased. Renal injury was attenuated in TLR4-/- mice which demonstrated less glomerular immunoglobulin and complement deposition. These results demonstrate that both TLR9 and TLR4 are required for 'full-blown' autoimmunity and organ injury in experimental lupus induced by pristane.

Endogenous foxp3(+) T-regulatory cells suppress anti-glomerular basement membrane nephritis

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.

Toll-like receptor 9 enhances nephritogenic immunity and glomerular leukocyte recruitment, exacerbating experimental crescentic glomerulonephritis

Glomerular disease can be triggered or exacerbated by microbes that activate the immune system by Toll-like receptor (TLR) ligation. TLR9 activation promotes host defenses through the enhancement of innate and adaptive immune responses that facilitate the recruitment of leukocytes to areas of inflammation. We defined the role of TLR9 in experimental crescentic glomerulonephritis. Wild-type mice administered a TLR9 ligand and sheep anti-mouse glomerular basement membrane antibody developed histological injury with impaired renal function, which was attenuated in TLR9 knockout mice. Consistent with enhanced renal injury, wild-type mice exhibited enhanced T helper 1 and T helper 17 cellular immune responses. Kidney mRNA expression of inflammatory cytokines and chemokines as well as leukocyte recruitment were increased in wild-type mice. The use of bone marrow chimeric mice demonstrated that while both bone marrow and tissue cell TLR9 are required for maximal injury, bone marrow TLR9 is more important. Administration of a TLR9 inhibitor before sheep anti-mouse glomerular basement membrane globulin in wild-type mice attenuated cellular nephritogenic immunity that resulted in decreased renal injury. Administration of the inhibitor 7 days after disease initiation decreased glomerular leukocyte recruitment as well as renal injury. These results define the role of TLR9 in experimental crescentic glomerulonephritis and identify therapeutic potential for TLR9 inhibitors in attenuating renal injury, decreasing cellular nephritogenic immunity early in disease, and decreasing kidney effector responses later.

Th17 cells promote autoimmune anti-myeloperoxidase glomerulonephritis

A major target autoantigen in anti-neutrophil cytoplasmic antibody-associated vasculitis is myeloperoxidase (MPO). Although MPO-specific CD4+ Th cells seem to orchestrate renal injury, the role of the Th17 subset is unknown. We hypothesized that Th17 cells direct injurious anti-MPO autoimmunity in experimental murine anti-MPO-induced glomerulonephritis (GN). We immunized mice with MPO to establish autoimmunity, resulting in systemic IL-17A production with MPO-specific dermal delayed-type hypersensitivity. We triggered disease using antibodies to the glomerular basement membrane to induce glomerular deposition of MPO by neutrophils. Wild-type mice developed necrotizing GN with an influx of glomerular leukocytes and albuminuria. In contrast, mice deficient in the key Th17 effector cytokine IL-17A were nearly completely protected. The protective effects resulted partly from reduced neutrophil recruitment, which led to less disposition of glomerular MPO. To test whether IL-17A also drives autoimmune delayed-type hypersensitivity in the kidney, we injected MPO into the kidneys of MPO-sensitized mice. IL-17A deficiency reduced accumulation of renal macrophages and renal CCL5 mRNA expression. In conclusion, IL-17A contributes to the pathophysiology of autoimmune anti-MPO GN, suggesting that it may be a viable therapeutic target for this disease.

Endogenous CD100 promotes glomerular injury and macrophage recruitment in experimental crescentic glomerulonephritis

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.

Macrophage migration inhibitory factor deficiency attenuates macrophage recruitment, glomerulonephritis, and lethality in MRL/lpr mice

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.

CD100 enhances dendritic cell and CD4+ cell activation leading to pathogenetic humoral responses and immune complex glomerulonephritis

CD100, a member of the semaphorin family, is a costimulatory molecule in adaptive immune responses by switching off CD72's negative signals. However, CD100's potential pathogenetic effects in damaging immune responses remain largely unexplored. We tested the hypothesis that CD100 plays a pathogenetic role in experimental immune complex glomerulonephritis. Daily injection of horse apoferritin for 14 days induced immune complex formation, mesangial proliferative glomerulonephritis and proteinuria in CD100-intact (CD100+/+) BALB/c mice. CD100-deficient (CD100-/-) mice were protected from histological and functional glomerular injury. They exhibited reduced deposition of Igs and C3 in glomeruli, reduced MCP-1 and MIP-2 intrarenal mRNA expression, and diminished glomerular macrophage accumulation. Attenuated glomerular injury was associated with decreased Ag-specific Ig production, reduced CD4+ cell activation and cytokine production. Following Ag injection, CD4+ cell CD100 expression was enhanced and dendritic cell CD86 expression was up-regulated. However, in CD100-/- mice, dendritic cell CD86 (but not CD80) up-regulation was significantly attenuated. Following i.p. immunization, CD86, but not CD80, promotes early Ag-specific TCR-transgenic DO11.10 CD4+ cell proliferation and IFN-gamma production, suggesting that CD100 expression enables full expression of CD86 and consequent CD4+ cell activation. Transfer of CD100+/+ DO11.10 cells into CD100-/- mice resulted in decreased proliferation demonstrating that CD100 from other sources in addition to CD100 from Ag-specific CD4+ cells plays a role in initial T cell proliferation. Although T cell-B cell interactions also may be relevant, these studies demonstrate that CD100 enhances pathogenetic humoral immune responses and promotes the activation of APCs by up-regulating CD86 expression.

Phospholipase C isozymes are differentially distributed in the rat adrenal medulla

Immunohistochemistry has been used to examine the distribution of selected phospholipase C (PLC) isozymes within the adrenal medulla of the rat. PLCbeta isozymes were expressed at moderate levels in the chromaffin cells but more strongly in association with ganglion cell clusters. PLCbeta2 and PLCbeta3 staining of clusters did not overlap suggesting selective PLC isozyme expression in two distinct ganglionic types. The distribution of PLCbeta4 immunoreactivity was very similar to PLCbeta3 with the strongest staining observed in the same cell clusters. Antibodies to PLCbeta1 labelled multiple bands on Western blots and were not therefore used for immunohistochemistry. The chromaffin cells were also immunoreactive for PLCgamma1, although the strongest staining with this antibody was seen in cells surrounding large sinus vessels. PLCdelta1 and PLCdelta2 had quite distinct distributions, with the former selectively localized to an endothelial cell population surrounding the chromaffin cells. This observation was supported by experiments on isolated bovine adrenal medullary cells where PLCdelta1 expression was lost when the cell preparation was enriched for chromaffin cells. Antibodies to PLCdelta2 labelled a network of nerve fibres throughout the medulla and clusters of ganglion cells located primarily at the medullary-cortical boundary. PLCdelta2 immunoreactivity was also present in nerve fibres within the adrenal capsule where it appeared to be co-localized with PLCbeta4 staining.

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.

A short synthesis of bicyclic dipeptides corresponding to Xxx-L-Pro Xxx-D-Pro having constrained trans-proline amides

[formula: see text] A short synthesis that generates two isomeric bicyclic dipeptides having constrained, trans-proline amide bonds has been developed. One of these bicyclic dipeptides corresponds to an Xxx-L-Pro dipeptide (4), while the other isomer corresponds to an Xxx-D-Pro dipeptide (5). The two isomers are readily distinguished by their 1H NMR spectra.

Molecular microbial diversity of an agricultural soil in Wisconsin

A culture-independent survey of the soil microbial diversity in a clover-grass pasture in southern Wisconsin was conducted by sequence analysis of a universal clone library of genes coding for small-subunit rRNA (rDNA). A rapid and efficient method for extraction of DNA from soils which resulted in highly purified DNA with minimal shearing was developed. Universal small-subunit-rRNA primers were used to amplify DNA extracted from the pasture soil. The PCR products were cloned into pGEM-T, and either hypervariable or conserved regions were sequenced. The relationships of 124 sequences to those of cultured organisms of known phylogeny were determined. Of the 124 clones sequenced, 98.4% were from the domain Bacteria. Two of the rDNA sequences were derived from eukaryotic organelles. Two of the 124 sequences were of nuclear origin, one being fungal and the other a plant sequence. No sequences of the domain Archaea were found. Within the domain, Bacteria, three kingdoms were highly represented: the Proteobacteria (16.1%), the Cytophaga-Flexibacter-Bacteroides group (21.8%), and the low G+C-content gram-positive group (21.8%). Some kingdoms, such as the Thermotogales, the green nonsulfur group, Fusobacteria, and the Spirochaetes, were absent. A large number of the sequences (39.4%) were distributed among several clades that are not among the major taxa described by Olsen et al. (G.J. Olsen, C.R. Woese, and R. Overbeek, J. Bacteriol., 176:1-6, 1994). From the alignments of the sequence data, distance matrices were calculated to display the enormous microbial diversity found in this soil in two ways, as phylogenetic trees and as multidimensional-scaling plots.