Autophagy in Immune-Related Renal Disease.

Autophagy is an important biology process, central to the maintenance of biology process in both physiological and pathological situations. It is regarded as a "double-edged sword"-exerting both protective and/or detrimental effects. These two-way effects are observed in immune cells as well as renal resident cells, including podocytes, mesangial cells, tubular epithelial cells, and endothelial cells of the glomerular capillaries. Mounting evidence suggests that autophagy is implicated in the pathological process of various immune-related renal diseases (IRRDs) as well as the kidney that underwent transplantation. Here, we provide an overview of the pathological role of autophagy in IRRDs, including lupus nephritis, IgA nephropathy, membrane nephropathy, ANCA-associated nephritis, and diabetic nephropathy. The understanding of the pathogenesis and regulatory mechanisms of autophagy in these renal diseases may lead to the identification of new diagnostic targets and refined therapeutic modulation.

Rho GTPases are involved in S1P-enhanced glomerular endothelial cells activation with anti-myeloperoxidase antibody positive IgG.

Sphingosine-1-phosphate (S1P) is a crucial regulator in vascular inflammation. Our recent study found that under pathophysiological concentration in active anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), S1P participated in MPO-ANCA-positive IgG-induced glomerular endothelial cell (GEnC) activation via a S1P receptor (S1PR)-dependent way. However, the downstream signalling pathways are not fully clear yet. In this study, we demonstrated that Rho guanosine triphosphatases (GTPases) signalling pathways, RhoA and Rac1 in particular, were implicated in MPO-ANCA-positive IgG-mediated GEnCs activation enhanced by pathophysiological concentration of S1P in AAV. These results provide mechanistic insights into vascular barrier dysfunction in AAV, which may facilitate the development of effective therapies.

In situ detection of PR3-ANCA+ B cells and alterations in the variable region of immunoglobulin genes support a role of inflamed tissue in the emergence of auto-reactivity in granulomatosis with polyangiitis.

Circulating anti-neutrophilic cytoplasmic autoantibodies targeting proteinase 3 (PR3-ANCA) are a diagnostic and pathogenic hallmark of granulomatosis with polyangiitis (GPA). It is, however, incompletely understood if inflamed tissue supports presence or emergence of PR3-ANCA+ B cells. In search of such cells in inflamed tissue of GPA, immunofluorescence staining for IgG and a common PR3-ANCA idiotype (5/7 Id) was undertaken. Few 5/7 Id+/IgG+ B cells were detected in respiratory and kidney tissue of GPA. To gain more insight into surrogate markers possibly indicative of an anti-PR3-response, a meta-analysis comprising IGVH and IGVL genes derived from respiratory tract tissue of GPA (231 clones) was performed. Next generation sequencing-based IGHV genes derived from peripheral blood of healthy donors (244.353 clones) and previously published IGLV genes (148 clones) served as controls. Additionally, Ig genes of three murine and five known human monoclonal anti-PR3 antibodies were analyzed. Primary and probably secondary rearrangements led to altered VDJ usage and an extended complementarity determining region 3 (CDR3) of IGHV clones from GPA tissue. Selection against amino acid exchanges was prominent in the framework region of IGHV clones from GPA tissue. The comparison of V(D)J rearrangements and deduced amino acid sequences of the CDR3 yielded no identities and few similarities between clones derived from respiratory tissue of GPA and anti-PR3 antibodies, arguing against a presence of B cells that carry PR3-ANCA-prone Ig genes among the clones. In line with the scarcity of 5/7 Id+ B lymphocytes in GPA tissue, the results suggest that with respect to a local anti-PR3 response, methods detecting rare clones are required.

Linked help from bacterial proteins drives autoantibody production in small vessel vasculitis.

The small vessel vasculitides granulomatosis with polyangiitis (GPA) and microscopic polyangiitis are associated with autoantibodies to neutrophil cytoplasm antigens (ANCA), principally proteinase-3 (PR3) and myeloperoxidase (MPO). There is an association between GPA and nasal carriage of Staphylococcus aureus. The recent finding that S. aureus produces proteins that bind tightly to and block the function of both PR3 and MPO suggests a mechanism for ANCA formation. The bacterial protein-autoantigen conjugate is recognised by B cells with ANCA specificity, internalised, and the bacterial protein processed and presented to T cells with specificity for bacterial peptides. The T cell can then provide help to the B cell, allowing class switching, affinity maturation and the production of pathogenic ANCA. This mechanism predicts that T cells with this specificity will be found in patients, and that the bacterial protein-autoantigen conjugate will be particularly efficient at eliciting ANCA production.

ANCA-Associated Vasculitis Pathogenesis: A Commentary.

PURPOSE OF REVIEW: The ANCA-associated vasculitides are a group of small vessel vasculitides characterized by autoantibodies recognizing the neutrophil cytoplasmic antigens PR3 and MPO. We examine the current clinical and molecular immunology understanding of ANCA-associated vasculitides and discuss the current needs in our understanding of the pathogenic mechanisms of these rare diseases. RECENT FINDINGS: The majority of efforts to understand the pathogenesis of these diseases have focused on dissecting neutrophil biology because the neutrophil is the primary expressor of ANCA autoantigens. However, a number of important genetic, clinical, and cellular biology observations suggest that attempts to understand the pathogenesis of ANCA vasculitides should move away from emphasis on the role of the neutrophil and instead re-focus on the potential role of other immune cell mediators. Whether or not neutrophils are the key determinant of ANCA-associated vasculitis pathogenesis should be revisited in detail. A neutrophil-centric view of the pathogenesis of these diseases cannot fully account for important genetic, clinical, and cellular biology observations that implicate important and under-appreciated roles for monocytes and T cells. Refocusing on these findings will likely lead to new discovery of novel therapeutic targets and the identification of clinically useful biomarkers for disease activity.

Characterization of the CD177 interaction with the ANCA antigen proteinase 3.

Proteinase 3 is a serine protease found in neutrophil granules and on the extracellular neutrophil membrane (mPR3). mPR3 is a major antigen for anti-neutrophil cytoplasmic antibodies (PR3-ANCAs), autoantibodies causing fatal autoimmune diseases. In most individuals, a subpopulation of neutrophils also produce CD177, proposed to present additional PR3 on the surface, resulting in CD177neg/mPR3low and CD177pos/mPR3high neutrophil subsets. A positive correlation has been shown between mPR3 abundance, disease incidence, and clinical outcome. We present here a detailed investigation of the PR3:CD177 complex, verifying the interaction, demonstrating the effect of binding on PR3 proteolytic activity and explaining the accessibility of major PR3-ANCA epitopes. We observed high affinity PR3:CD177 complex formation by surface plasmon resonance. Using flow cytometry and a PR3-specific FRET assay, we found that CD177 binding reduced the proteolytic activity of PR3 in vitro using purified proteins, in neutrophil degranulation supernatants containing wtPR3 and directly on mPR3high neutrophils and PR3-loaded HEK cells. Finally, CD177pos/mPR3high neutrophils showed no migration advantage in vitro or in vivo when migrating from the blood into the oral cavity. We illuminate details of the PR3:CD177 interaction explaining mPR3 membrane orientation and proteolytic activity with relevance to ANCA activation of the distinct mPR3 neutrophil populations.

Heterogeneity of Human Neutrophil CD177 Expression Results from CD177P1 Pseudogene Conversion.

Most humans harbor both CD177neg and CD177pos neutrophils but 1-10% of people are CD177null, placing them at risk for formation of anti-neutrophil antibodies that can cause transfusion-related acute lung injury and neonatal alloimmune neutropenia. By deep sequencing the CD177 locus, we catalogued CD177 single nucleotide variants and identified a novel stop codon in CD177null individuals arising from a single base substitution in exon 7. This is not a mutation in CD177 itself, rather the CD177null phenotype arises when exon 7 of CD177 is supplied entirely by the CD177 pseudogene (CD177P1), which appears to have resulted from allelic gene conversion. In CD177 expressing individuals the CD177 locus contains both CD177P1 and CD177 sequences. The proportion of CD177hi neutrophils in the blood is a heritable trait. Abundance of CD177hi neutrophils correlates with homozygosity for CD177 reference allele, while heterozygosity for ectopic CD177P1 gene conversion correlates with increased CD177neg neutrophils, in which both CD177P1 partially incorporated allele and paired intact CD177 allele are transcribed. Human neutrophil heterogeneity for CD177 expression arises by ectopic allelic conversion. Resolution of the genetic basis of CD177null phenotype identifies a method for screening for individuals at risk of CD177 isoimmunisation.

Induction of proteinase 3-anti-neutrophil cytoplasmic autoantibodies by proteinase 3-homologous bacterial protease in mice.

Proteinase 3 (PR3) is the principal target of antineutrophil cytoplasmic autoantibodies (ANCA) associated with granulomatosis with polyangiitis. The aim of this study was to investigate whether bacterial PR3-homologous protease can induce autoantibodies to PR3 and ANCA-associated pathology in mice. Among the bacterial proteases that have greater than 30 % identity with PR3, a trypsin-like serine protease of Saccharomonospora viridis, a bacterium that causes hypersensitivity pneumonitis, was chosen. When the mice were immunized with the recombinant protease of S. viridis (SvPR), 75 % of NZBWF1 and 100 % of C57BL/6 mice developed high levels of autoantibodies to mouse PR3 (mPR3). The levels of antibodies to mPR3 had a strong positive correlation with those to SvPR. In addition, more than half of the mPR3-reactive sera (63 %) reacted to purified human PR3 (hPR3), and the levels of antibodies to hPR3 had a positive correlation with those to mPR3. The sera from the immunized mice strongly stained murine neutrophils in a C-ANCA pattern. Although granulomatous inflammation and signs of vasculitis were observed in several mice, they were attributable to the use of complete Freund's adjuvant in the immunization. Collectively, exposure to PR3-homologous bacterial protease could induce ANCA in mice, and this finding may provide a new insight into the triggering mechanisms for the production of PR3-ANCA.

High mobility group box 1 contributes to anti-neutrophil cytoplasmic antibody-induced neutrophils activation through receptor for advanced glycation end products (RAGE) and Toll-like receptor 4.

INTRODUCTION: High mobility group box-1 (HMGB1), a typical damage-associated molecular pattern (DAMP) protein, is associated with inflammatory conditions and tissue damage. Our recent study found that circulating HMGB1 levels could reflect the disease activity of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The current study aimed to investigate whether HMGB1 participated in ANCA-induced neutrophil activation, which is one of the most important pathogenic aspects in the development of AAV. METHODS: The various effects of HMGB1 in ANCA-induced neutrophil activation were measured. Antagonists for relevant receptors and signaling molecules were employed. RESULTS: ANCA antigens translocation on neutrophils primed with HMGB1 was significantly higher than non-primed neutrophils. The levels of respiratory burst and degranulation increased significantly in HMGB1-primed neutrophils activated with ANCA-positive IgG, as compared with non-primed neutrophils. Furthermore, blocking Toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE), rather than TLR2, resulted in a significant decrease in HMGB1-induced ANCA antigens translocation, respiratory burst and degranulation. Similar effects were also found when blocking MyD88 and NF-κB. CONCLUSIONS: HMGB1 could prime neutrophils by increasing ANCA antigens translocation, and the primed neutrophils could be further induced by ANCA, resulting in the respiratory burst and degranulation. This process is TLR4- and RAGE-dependent through the MyD88/NF-κB pathway.

CD14 expression is increased on monocytes in patients with anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis and correlates with the expression of ANCA autoantigens.

Monocyte subsets with differing functional properties have been defined by their expression of CD14 and CD16. We investigated these subsets in anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) and determined their surface expression of ANCA autoantigens. Flow cytometry was performed on blood from 14 patients with active AAV, 46 patients with AAV in remission and 21 controls. The proportion of classical (CD14(high) CD16(neg/low)), intermediate (CD14(high) CD16(high)) and non-classical (CD14(low) CD16(high)) monocytes and surface expression levels of CD14 and CD16 were determined, as well as surface expression of proteinase 3 (PR3) and myeloperoxidase (MPO) on monocyte subsets. There was no change in the proportion of monocytes in each subset in patients with AAV compared with healthy controls. The expression of CD14 on monocytes from patients with active AAV was increased, compared with patients in remission and healthy controls (P < 0.01). Patients with PR3-ANCA disease in remission also had increased monocyte expression of CD14 compared with controls (P < 0.01); however, levels in patients with MPO-ANCA disease in remission were lower than active MPO-ANCA patients, and not significantly different from controls. There was a correlation between CD14 and both PR3 and MPO expression on classical monocytes in AAV patients (r = 0.79, P < 0.0001 and r = 0.42, P < 0.005, respectively). In conclusion, there was an increase in monocyte CD14 expression in active AAV and PR3-ANCA disease in remission. The correlation of CD14 expression with ANCA autoantigen expression in AAV may reflect cell activation, and warrants further investigation into the potential for increased CD14 expression to trigger disease induction or relapse.

Proinflammatory progranulin antibodies in inflammatory bowel diseases.

BACKGROUND: Recently, we identified neutralizing autoantibodies against progranulin (PGRN) in a wide spectrum of rheumatic diseases including cases with enteropathic spondylarthritis. PGRN is a secreted protein with strong anti-inflammatory effects, believed to be mediated by the direct inhibition of TNF receptors 1&2. Given the central role of TNF-α as proinflammatory cytokine, a neutralizing antibody directed against its physiologic antagonist PGRN might entertain a proinflammatory environment. OBJECTIVE: The aim of the present study was to investigate a possible occurrence of PGRN-antibodies (PGRN-Abs) in inflammatory bowel disease (IBD), and to investigate a possible pathogenic effect. MATERIALS AND METHODS: Sera samples of 141 patients with Crohn's disease (CD) and of 71 patients with ulcerative colitis (UC) were tested for PGRN-Abs by ELISA. PGRN plasma levels were detected by ELISA. Proinflammatory effects of progranulin-antibodies were analyzed by TNF-α-mediated cytotoxicity assays using HT29 cells and by examination of possible effects of PGRN and of PGRN-antibodies on TNF-α-induced downmodulation of FOXP3 expression in CD4(+)CD25(hi) Tregs. RESULTS: PGRN-Abs were found in sera of 23/141 (16.31%) patients with CD, and 15/71 (21.13%) patients with UC. PGRN-Abs were more frequent than anti-neutrophil cytoplasmic autoantibodies (ANCAs) in UC, but less frequent than anti-Saccharomyces cerevisiae antibodies (ASCAs) in CD. PGRN-Abs belonged mostly to IgG1 (71.1%) and IgA (26.3%). They occurred in relevant titres and had significant neutralizing effects on PGRN plasma levels. Cytotoxicity assays comparing PGRN-antibody-positive sera with negative sera from matched patients with IBD showed a proinflammatory effect of PGRN-Abs on HT29 cells. Moreover, PGRN-antibodies led to an increase of TNF-α-induced downmodulation of FOXP3 in CD4(+)CD25(hi) Tregs. CONCLUSION: The results suggest that PGRN-Abs occur frequently in CD and UC, and have a proinflammatory effect.

Enhanced formation and disordered regulation of NETs in myeloperoxidase-ANCA-associated microscopic polyangiitis.

Microscopic polyangiitis (MPA) is an ANCA-associated vasculitis that affects small vessels, especially renal glomeruli. We recently demonstrated that the abnormal formation and impaired degradation of neutrophil extracellular traps (NETs) may be crucially involved in the generation of myeloperoxidase (MPO)-ANCA and subsequent development of MPA. This study assessed the formation and regulation of NETs in patients with MPO-ANCA-associated MPA. Peripheral blood samples were obtained from 38 patients with MPO-ANCA-associated MPA, 23 patients with systemic lupus erythematosus (SLE), and 8 healthy controls. IgG eluted from MPO-ANCA-associated MPA sera demonstrated the highest ability to induce NETs, and this ability correlated with disease activity and paralleled ANCA affinity for MPO. Moreover, addition of recombinant human MPO to these IgG samples reduced NET induction. Additionally, MPO-ANCA-associated MPA sera exhibited lower rates of NET degradation that recovered partially upon depletion of IgG. The activity of DNase I, an important regulator of NETs, was also lower in MPO-ANCA-associated MPA and SLE sera. IgG depletion from MPO-ANCA-associated MPA sera partially restored the rate of NET degradation, and addition of DNase I synergistically enhanced this restoration. Addition of anti-MPO antibodies did not inhibit DNase I activity, and some MPO-ANCA-associated MPA sera contained anti-NET antibodies at levels not correlated with MPO-ANCA titers, suggesting the involvement of unidentified autoantibodies as well. The collective evidence suggests a vicious cycle involving MPO-ANCA and the regulation of NETs could be critically involved in the pathogenesis of MPO-ANCA-associated MPA.

Periaortitis associated with anti-neutrophil cytoplasmic antibodies induced by bevacizumab combination therapy.

Drug-induced vessel vasculitis is a rare complication of chemotherapy. In particular, few reports have investigated drug-induced large vessel vasculitis. We herein report the case of a 57-year-old woman with advanced lung adenocarcinoma who developed perinuclear anti-neutrophil cytoplastic antibodies (p-ANCA)-positive periaortitis induced by bevacizumab combination chemotherapy. With the increasing use of combination therapy with bevacizumab, the incidence of vascular complications will potentially increase. A noninfectious fever occurring during chemotherapy might be a sign of vasculitis; therefore, we must ensure that possible periaortitis is not overlooked.

Extensive endoscopic image-guided sinus surgery decreases BPI-ANCA in patients with cystic fibrosis.

Antineutrophil cytoplasm autoantibodies (ANCA) directed against bactericidal/permeability-increasing protein (BPI) are common in patients with cystic fibrosis (CF), and serum levels are correlated with lung colonization by Pseudomonas aeruginosa and the severity of lung damage. The production of BPI-ANCA may be due to the costimulation of BPI when mounting an immune response against P. aeruginosa. The effect of surgery aiming to eradicate bacteria and infected tissue on BPI-ANCA levels is sparsely described. A cohort of patients with CF were included: 53 patients having extensive image-guided sinus surgery (EIGSS) with topical postoperative antibiotic treatment, 131 non-operated controls and 36 who had double lung transplantation (LTX). In all 219 patients, serum samples before and after surgery or at similar intervals were analysed for IgG and IgA BPI-ANCA. The EIGSS group showed a highly significant decrease in both IgA and IgG BPI-ANCA levels compared with their own preoperative values and control group values (P < 0.001-0.02). The LTX patients also showed a highly significant decrease in both IgA and IgG BPI-ANCA levels (P < 0.001). EIGSS and LTX decrease IgA and IgG BPI-ANCA levels in patients with CF, indicating that extensive removal of infected tissue influences the pathogenic process of autoantibody production. The results shown herein are in favour of applying EIGSS in selected patients with CF and for using BPI-ANCA as a surrogate marker for guiding further therapeutic interventions.

Rituximab en el tratamiento de las vasculitis asociadas a ANCA: ¿el futuro hoy? / Rituximab for the treatment of ANCA associated vasculitis. The future today?

Gracias al tratamiento con ciclofosfamida la letalidad de las vasculitis asociadas a ANCA ha disminuido considerablemente. Sin embargo, dicho tratamiento se relaciona con efectos adversos agudos y crónicos que contribuyen a la morbimortalidad de estas enfermedades. Por ello, uno de los retos actuales en el manejo de estas patologías consiste en encontrar terapias que sean tan efectivas como la ciclofosfamida pero con un margen de seguridad más favorable. Bajo estas condiciones, el rituximab (RTX), un anticuerpo monoclonal anti-CD20, encabeza la lista de nuevas opciones en el tratamiento de las vasculitis asociadas a ANCA y es el más firme candidato para establecerse como opción terapéutica de primera elección. En este artículo de revisión examinamos la evidencia actual sobre la eficacia y seguridad de RTX como tratamiento para las vasculitis de vasos de pequeño calibre asociadas a ANCA (AU)

Since cyclophosphamide was introduced for the treatment of ANCA-associated vasculitis, the mortality of these diseases has decreased considerably. However, such treatment is related to acute and chronic serious adverse effects, which contribute to the morbidity and mortality of such diseases. Therefore, one of the main challenges in the treatment of such conditions is to find newer and effective therapies with a safer profile. Rituximab (RTX), an anti-CD20 monoclonal antibody stands at the top of new options for the treatment of ANCA-associated vasculitis, and is the strongest candidate to establish itself as a first choice therapeutic agent. Here, we review the rationale of RTX treatment in ANCA-associated small vessel vasculitis, and the current evidence of both its efficacy and toxicity (AU)

[Rituximab for the treatment of ANCA associated vasculitis: the future today?]. / Rituximab en el tratamiento de las vasculitis asociadas a ANCA: ¿el futuro hoy?

Since cyclophosphamide was introduced for the treatment of ANCA-associated vasculitis, the mortality of these diseases has decreased considerably. However, such treatment is related to acute and chronic serious adverse effects, which contribute to the morbidity and mortality of such diseases. Therefore, one of the main challenges in the treatment of such conditions is to find newer and effective therapies with a safer profile. Rituximab (RTX), an anti-CD20 monoclonal antibody stands at the top of new options for the treatment of ANCA-associated vasculitis, and is the strongest candidate to establish itself as a first choice therapeutic agent. Here, we review the rationale of RTX treatment in ANCA-associated small vessel vasculitis, and the current evidence of both its efficacy and toxicity.

Carbimazole-induced agranulocytosis: does antineutrophil cytoplasmic antibody have a role?

Carbimazole is a drug that is widely used for hyperthyroid disorders, such as Graves' disease. Agranulocytosis is a rare idiosyncratic adverse reaction to the drug which is potentially fatal. This report describes a patient with a history of successfully treated pyoderma gangrenosum, who developed agranulocytosis 3 weeks after commencement of carbimazole for Graves' disease. It may give credence to the theory that implicates antineutrophil cytoplasmic antibodies in the pathogenesis of agranulocytosis induced by antithyroid drugs.

Autoantibodies in silicosis patients and in silica-exposed individuals.

The aim of this study was to evaluate the prevalence of autoantibodies in silica-exposed patients with and without silicosis and without any known rheumatic disease. We studied 61 males exposed to silica for a mean time of 12.2 +/- 10.2 years of exposure. A total of 72.1% (44/61) of them presented with pulmonary silicosis. As control group we included 62 healthy males. In all samples we screened for rheumatoid factor (latex agglutination), antinuclear antibodies (indirect immunofluorescence), anti Scl-70 (ELISA) and ANCA (indirect immunofluorescence technique). One patient (1.6%) of the silica group had weakly positive ANA (titer 1:80, centromeric pattern); one (1.6%) had atypical ANCA and seven patients (11.4%) presented positive rheumatoid factor (values range from 8 to 32 UI/ml). One control patient had a positive RF and none of them had positive ANA or ANCA. All patients and controls were negative for anti-Scl-70. The finding of positive RF was higher in the silica-exposed patients (p = 0.032; Fisher). All patients with positive RF had pulmonary silicosis. In the silica-exposed group we could not find a relationship between the presence of RF and age (p = 0.21; Mann-Whitney), smoking habits (p = 0.25; Fisher) but a positive relationship was found with exposure time to silica dust (p = 0.005; Mann-Whitney). We conclude that there was 11.4% prevalence of low titer RF in the silica-exposed patients without known rheumatic disease. RF was more common in patients with longer exposure to silica dust and appeared only in those with silicosis. The presence of ANA, Scl-70 and ANCA was the same as in the control population.

Successful pregnancy and delivery of a healthy newborn despite transplacental transfer of antimyeloperoxidase antibodies from a mother with microscopic polyangiitis.

Myeloperoxidase (MPO)-specific antineutrophil cytoplasmic antibodies have been proposed as pathogenic for microscopic polyangiitis. Supporting this hypothesis, a case report of transplacental anti-MPO antibody transfer presumably causing a vasculitis-like syndrome in the newborn is cited frequently. Here, we report a case of transplacental transfer of high levels of anti-MPO antibodies not resulting in clinical compromise in the newborn. The mother developed microscopic polyangiitis 5 years before the pregnancy. After induction therapy, remission was maintained with low-dose prednisone and azathioprine for 4.5 years despite high levels of anti-MPO antibodies (>100 U/mL). The patient elected to become pregnant, immunosuppression was maintained during pregnancy, and a normal-term neonate was delivered. The newborn's venous blood anti-MPO antibody levels decreased gradually from greater than 100 U/mL at birth to undetectable by day 120. No clinical manifestation of vasculitis developed in the newborn. This case supports that anti-MPO antibodies alone are not pathogenic without additional cofactors.