Reduced CD5(+) CD24(hi) CD38(hi) and interleukin-10(+) regulatory B cells in active anti-neutrophil cytoplasmic autoantibody-associated vasculitis permit increased circulating autoantibodies

Pathogenesis of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis is B cell-dependent, although how particular B cell subsets modulate immunopathogenesis remains unknown. Although their phenotype remains controversial, regulatory B cells (Bregs ), play a role in immunological tolerance via interleukin (IL)-10. Putative CD19(+) CD24(hi) CD38(hi) and CD19(+) CD24(hi) CD27(+) Bregs were evaluated in addition to their CD5(+) subsets in 69 patients with ANCA-associated vasculitis (AAV). B cell IL-10 was verified by flow cytometry following culture with CD40 ligand and cytosine-phosphate-guanosine (CpG) DNA. Patients with active disease had decreased levels of CD5(+) CD24(hi) CD38(hi) B cells and IL-10(+) B cells compared to patients in remission and healthy controls (HCs). As IL-10(+) and CD5(+) CD24(hi) CD38(hi) B cells normalized in remission within an individual, ANCA titres decreased. The CD5(+) subset of CD24(hi) CD38(hi) B cells decreases in active disease and rebounds during remission similarly to IL-10-producing B cells. Moreover, CD5(+) B cells are enriched in the ability to produce IL-10 compared to CD5(neg) B cells. Together these results suggest that CD5 may identify functional IL-10-producing Bregs . The malfunction of Bregs during active disease due to reduced IL-10 expression may thus permit ANCA production.

Pathways to renal biopsy and diagnosis among patients with ANCA small-vessel vasculitis

OBJECTIVES

Antineutrophil cytoplasmic antibody small-vessel vasculitis (ANCA-SVV) is an autoimmune systemic process increasingly recogniSed since the advent of antibody testing for the disease. Prompt diagnosis and institution of immunosuppressive therapy has been shown to improve patient outcome. The goal of this study was to better understand how patients navigate the health care system from symptom presentation to biopsy diagnosis, and to study the effects of prompt versus delayed diagnosis.

METHODS

Disease symptoms and number of physicians seen prior to renal biopsy were assessed for 127 ANCA-SVV patients. Direct, delayed, and quest pathways to diagnosis and treatment of vasculitis were defined for both patients and providers. Kruskal-Wallis and Fisher exact tests were used to evaluate continual measures and compare categorical variables across pathways.

RESULTS

Among patients who sought direct care, physician delay in referral to a nephrologist was common (49/127, 71%, p=0.0023). Patients who delayed seeking care also experienced a delayed diagnosis 57% of the time (p=0.0023). Patients presenting with prodromal flu or upper respiratory involvement were more likely to have a delay/quest patient pathway (56% and 55%, respectively) than a direct patient pathway (44%, p=0.033 and 45%, p=0.019, respectively). There was a trend for patients with more severe loss of renal function to have a more direct referral to a nephrologist.

CONCLUSIONS

Delay in diagnosis of ANCA SVV may be due to lack of or non-specific symptoms, especially in patients who present with non-renal manifestations of disease. Better algorithms are needed to identify extra-renal manifestations, expedite diagnosis and improve patient outcomes.

Epigenetics and complementary proteins

Although studies on the immunopathogenesis of anti-neutrophil cytoplasm antibody (ANCA) vasculitis have been directed at understanding the autoantibody, there is growing evidence that points to the importance of ANCA autoantigen genes and their regulation. Transcriptional analysis indicates that ANCA autoantigen genes are active in mature neutrophils of ANCA vasculitis patients compared to healthy controls. The unusual transcriptional state of neutrophils from ANCA vasculitis patients appears to be a consequence of failed or disrupted epigenetic silencing. Defective epigenetic silencing could have global effects, by altering the transcriptional and phenotypic state of neutrophils, or local effects by permitting transcription of autoantigen genes from both strands resulting in anti-sense transcripts. Although the role of anti-sense transcripts is currently unknown, there are two intriguing possibilities. Anti-sense transcripts could function (as described for other genes) in transcriptional silencing of autoantigen genes, which takes place in normal neutrophil progenitors. In the setting of failed epigenetic silencing, the fate of anti-sense transcripts may be pathological and serve as a template for production of complementary autoantigens. The observation that ANCA vasculitis patients have anti-sense transcripts and antibodies to complementary proteins is consistent with a role of anti-sense transcripts in complementary protein production. A better understanding of epigenetic silencing and complementary proteins in ANCA vasculitis may unlock the underlying pathology of this condition.

Leukocyte gene expression signatures in antineutrophil cytoplasmic autoantibody and lupus glomerulonephritis

Leukocytes play a major role in the development and progression of autoimmune diseases. We measured gene expression differences in leukocytes from patients that were antineutrophil cytoplasmic autoantibody (ANCA) positive, patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA), and healthy donors to explore potential pathways for clinical intervention. Leukocyte gene expression profiles were determined on Affymetrix U133A/B chips in 88 autoimmune patients, 28 healthy donors, and healthy donor leukocyte cell subtypes that were activated in vitro. Comparison of gene expression in leukocytes identified differentially expressed signature genes that distinguish each donor source. The microarray expression levels for many signature genes correlated with the clinical activity of small vessel vasculitis in the ANCA patients; a result confirmed by quantitative real time-polymerase chain reaction for 16 relevant genes. Comparison with in vitro-activated leukocyte subtypes from healthy donors revealed that the ANCA signature genes were expressed by neutrophils while the SLE signature genes were expressed in activated monocytes and T cells. We have found that leukocyte gene expression data can differentiate patients with RA, SLE, and ANCA-related small vessel vasculitis. Monitoring changes in the expression of specific genes may be a tool to help quantify disease activity during treatment.

The role of pathology in the diagnosis of systemic vasculitis

Pathologic processes are underlying defining features of systemic vasculitis. When these pathologic processes can not be observed directly, surrogate signs and symptoms of disease must be used to conclude that vasculitis is present in a patient and, if so, to determine what specific type of vasculitis is present. This review briefly describes the most defining pathologic features of giant cell arteritis, Takayasu arteritis, polyarteritis nodosa, Henoch-Schönlein purpura, cryoglobulinemic vasculitis, Kawasaki disease, microscopic polyangiitis, Wegener's granulomatosis and Churg-Strauss syndrome; and discusses how these pathologic features can be integrated with clinical and laboratory data to reach an actionable diagnosis.

Interleukin-18, neutrophils, and ANCA

Hewins et al. show that IL-18 is expressed in the kidneys of patients with ANCA-associated glomerulonephritis, and that IL-18 primes neutrophils via p38 MAPK. These findings suggest a role for IL-18, including IL-18-induced T(H)1 polarization and IFN-gamma production, in the progression of ANCA disease.

Clinical and pathologic characteristics of focal segmental glomerulosclerosis pathologic variants

Histologic variants of idiopathic focal segmental glomerulosclerosis (FSGS) may have prognostic value. A recent working classification system has distinguished five FSGS variants. We evaluated a cohort of adult patients with biopsy-proven FSGS diagnosed between March 1982 and July 2001 to determine if subtypes were associated with renal outcome. Renal biopsies were reviewed by two pathologists. Demographic and clinical data were obtained from charts. Outcomes were partial and complete remission of the nephrotic syndrome, and renal failure. The frequency of FSGS variants was: 3% cellular (N=6), 11% collapsing (N=22), 17% tip lesion (N=34), 26% perihilar (N=52), and 42% not otherwise specified (NOS) (N=83). Collapsing FSGS affected younger and more often black patients. Black race was uncommon in tip variant. Collapsing and tip variants had higher proteinuria and lower serum albumin than perihilar and NOS variants. Better renal function and less severe tubulointerstitial injury were observed in patients with tip variant. These patients were more likely to receive steroids and more often achieved complete remission (50%). After a median follow-up of 1.8 years, 23% of patients were on dialysis and 28% had renal failure. Collapsing FSGS had worse 1-year (74%) and 3-year (33%) renal survival compared to other variants (overall cohort renal survival at 1 and 3 years: 86 and 67%). Different histologic variants of FSGS have substantial differences in clinical features at the time of biopsy diagnosis and substantial differences in renal outcomes.

Mapping of myeloperoxidase epitopes recognized by MPO-ANCA using human-mouse MPO chimers

Myeloperoxidase (MPO) is one of the major target antigens of antineutrophil cytoplasmic autoantibodies (ANCA) found in patients with small-vessel vasculitis and pauci-immune necrotizing glomerulonephritis. To date, the target epitopes of MPO-ANCA remain poorly defined. Human MPO-ANCA do not typically bind mouse MPO. We utilized the differences between human and mouse MPO to identify the target regions of MPO-ANCA. We generated five chimeric MPO molecules in which we replaced different segments of the human or mouse molecules with their homologous counterpart from the other species. Of serum samples from 28 patients screened for this study, 43 samples from 14 patients with MPO-ANCA-associated vasculitis were tested against recombinant human and mouse MPO and the panel of chimeric molecules. Sera from 64 and 71% of patients bound to the carboxy-terminus of the heavy chain, in the regions of amino acids 517-667 or 668-745, respectively. No patient serum bound the MPO light chain or the amino-terminus of the heavy chain. All sera bound to only one or two regions of MPO. Although the pattern of MPO-ANCA binding changed over time (4-27 months) in 6 of 10 patients with several serum samples, such changes were infrequent. Other target regions of MPO-ANCA may not have been detected due to conformational differences between the native and recombinant forms of MPO. MPO-ANCA do not target a single epitope, but rather a small number of regions of MPO, primarily in the carboxy-terminus of the heavy chain.

Difference in antigenic determinant profiles between human and rat myeloperoxidase

We tested whether rat and human MPO have similar antigenic determinants using 36 human MPO-ANCA positive sera, one mouse anti-rat MPO and four mouse anti-human MPO monoclonal reagents. Purified rat and human MPO were used in ELISA, with or without crossinhibition by preincubation with human MPO or irrelevant antigen in the liquid phase. Only one human MPO ANCA positive serum exhibited significant binding in rat MPO ELISA. This binding was poorly inhibited by preincubation with human MPO in the liquid phase, but was conserved after adsorption of non specific anti-rat activity in a chromatography column. Three mouse anti-human MPO IgG monoclonal antibodies did not recognize rat MPO. Only one mouse anti-human MPO IgA monoclonal antibody bound to rat MPO. This binding was poorly inhibited by preincubation with human MPO (35% at 2 micro g/ml). Conversely, the mouse anti-rat MPO monoclonal did not bind human MPO. We have concluded that: (1) Most human MPO-ANCA recognize antigenic determinants on human MPO which are absent on rat MPO. Therefore, human auto-antibodies bind to epitopes which recently appeared after species evolution; (2) Inversely, the mouse anti-rat MPO monoclonal do not bind human MPO. Therefore, rat MPO epitopes have been altered during species evolution; (3) Mice injected with human MPO preferentially develop antibodies against xeno-epitopes which are not present in rodents. Therefore, human MPO may not be the best antigen to raise ANCA in animal models and (4) A comparison of the amino acid sequences of rat and human MPO may help elucidate the major antigenic epitopes.

Microscopic polyangiitis (microscopic polyarteritis)

Microscopic polyangiitis ("microscopic polyarteritis") is a form of necrotizing small vessel vasculitis that most often affects venules, capillaries, arterioles, and small arteries, although it occasionally involves medium-sized arteries. Microscopic polyangiitis is a more appropriate name than microscopic polyarteritis because some patients have no evidence for arterial involvement. The absence or paucity of immunoglobulin localization in vessel walls distinguishes microscopic polyangiitis from immune complex mediated small vessel vasculitis, such as Henoch-Schonlein purpura and cryoglobulinemic vasculitis. Clinical, epidemiological, and pathologic differences warrant the separation of microscopic polyangiitis from polyarteritis nodosa on the basis of involvement of capillaries and venules by the former but not the latter. Pauci-immune necrotizing and crescentic glomerulonephritis, and hemorrhagic pulmonary capillaritis are common in patients with microscopic polyangiitis. Microscopic polyangiitis is the most common cause for pulmonary-renal vasculitic syndrome. The vasculitis in patients with microscopic polyangiitis is pathologically indistinguishable from the vasculitis of Wegener's granulomatosis and Churg-Strauss syndrome. Granulomatous inflammation distinguishes Wegener's granulomatosis from microscopic polyangiitis. Asthma and eosinophilia distinguish Churg-Strauss syndrome from microscopic polyangiitis. Microscopic polyangiitis, Wegener's granulomatosis, and Churg-Strauss syndrome are all associated with circulating antineutrophil cytoplasmic autoantibodies.

Internalization of proteinase 3 is concomitant with endothelial cell apoptosis and internalization of myeloperoxidase with generation of intracellular oxidants

The important issue addressed by the studies presented here is the mechanism of neutrophil-mediated damage to endothelial and epithelial cells during inflammation. Binding of neutrophil-released granule proteins to endothelial cells may be involved in vascular damage in patients with inflammatory vascular diseases. We have determined whether granule proteins proteinase 3(PR3) and/or myeloperoxidase (MPO) are internalized into endothelial cells, as examined by UV light, confocal, and electron microscopy. Coincident induction of apoptosis and/or the generation of intracellular oxidants were monitored. The results indicate that human endothelial cells (human umbilical vein endothelial cells, human umbilical arterial endothelial cells, human lung microvascular endothelial cells) internalize both PR3 and MPO, which are detected on the cell surface, in the cytoplasm, and possibly nuclear. Epithelial cells (small airway epithelial cells) internalized MPO but not PR3, implying that the mechanism of PR3 internalization may be cell-type specific and different from that of MPO. Internalization of PR3, but not MPO, correlated with activation of apoptosis. Internalization of MPO correlated with an increase in intracellular oxidant radicals. The requirement for the proteolytic activity of PR3 for the induction of apoptosis was examined by generating PR3-truncated fragments that did not contain the components of the catalytic triad. An apoptotic function was localized to the C-terminal portion of PR3. These studies reveal novel mechanisms by which the neutrophil granule proteins PR3 and MPO contribute to tissue injury at sites of inflammation.

Theodore E. Woodward Award. Do ANCA cause small vessel vasculitis?

ANCA may be a pathogenetic force, but to date, support for this contention remains indirect. Active immunization with antigen or passive transfer of ANCA has not reproduced small vessel vasculitis (SVV). It is more than likely that if ANCA are pathogenetic, they are involved as one of many simultaneously occurring mechanisms acting in concert with other synergistic inflammatory mediators of disease. These include not only environmental factors such as infection or environmental toxins such as silica, but also genetic factors that are only now being described. The paradigm for this autoimmune process must include several events that occur simultaneously or sequentially, including ANCA, leukocyte activation and injured endothelium.

Restriction in V kappa gene use and antigen selection in anti-myeloperoxidase response in mice

Anti-neutrophil cytoplasmic Abs, directed primarily toward myeloperoxidase (MPO) and proteinase 3, are detected in the majority of patients with distinct forms of small vessel vasculitides and pauci-immune necrotizing glomerulonephritis. However, the origin of these autoantibodies remains unknown. We studied the V region gene use in murine anti-MPO Abs derived from Spontaneous Crescentic Glomerulonephritis/Kinjoh mice. A total of 13 anti-MPO-producing hybridomas were generated from four unimmunized mice. Ten of the 13 hybridomas (corresponding to 3 of 4 clones) expressed Vkappa1C but differed in their use of VH genes. The remaining three hybridomas expressed a Vkappa5 gene. Anti-MPO hybridomas from individual mice were derived from single clones as deduced by sequence similarity and splice-site identity. We found a statistically significant bias of amino acid replacement mutations to the complementarity-determining regions (CDR) in the Vkappa1C-expressing hybridomas. Intriguingly, all 10 Vkappa1C hybridomas share a lysine to glutamate mutation in the CDR1. To determine the effects of somatic V gene mutations on binding to MPO, we generated an anti-MPO Ab with an unmutated Vkappa1C L chain and compared its ability to bind MPO with its mutated counterpart. The mutated hybridoma-derived Ab has a 4.75-fold higher avidity for MPO than the unmutated Ab. These results suggest that: 1) the L chain plays a dominant role in determining Ab specificity to MPO, 2) the anti-MPO Ab response is oligoclonal, consistent with Ag selection, and 3) MPO is a driving Ag in the murine anti-MPO Ab response.

Do vasculitis categorization systems really matter?

The diagnosis of systemic vasculitides is challenging for many reasons. The etiology and pathogenesis of most vasculitides are unknown or incompletely known. Vasculitides have protean and overlapping clinical and pathologic features. There are conflicting if not contradictory approaches to diagnostic categorization. In spite of these challenges, precise diagnostic categorization is essential for appropriate treatment. This overview reviews the history behind the modern approach to diagnosis of selected vasculitides, including giant cell arteritis, Takayasu arteritis, polyarteritis nodosa, Kawasaki disease, Henoch-Schönlein purpura, cryoglobulinemic vasculitis, Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. Evidence is provided that the categorization for systemic vasculitis really does matter.

False-positive myeloperoxidase binding activity due to DNA/anti-DNA antibody complexes: a source for analytical error in serologic evaluation of anti-neutrophil cytoplasmic autoantibodies

Anti-myeloperoxidase antibodies (anti-MPO) are a major type of anti-neutrophil cytoplasmic antibody (ANCA). While evaluating anti-MPO monoclonal antibodies from SCG/Kj mice, we observed several hybridomas that appeared to react with both MPO and DNA. Sera from some patients with systemic lupus erythematosus (SLE) also react with MPO and DNA. We hypothesized that the MPO binding activity is a false-positive result due to the binding of DNA, contained within the antigen binding site of anti-DNA antibodies, to the cationic MPO. Antibodies from tissue culture supernatants from 'dual reactive' hybridomas were purified under high-salt conditions (3 M NaCl) to remove any antigen bound to antibody. The MPO and DNA binding activity were measured by ELISA. The MPO binding activity was completely abrogated while the DNA binding activity remained. The MPO binding activity was restored, in a dose-dependent manner, by the addition of increasing amount of calf-thymus DNA (CT-DNA) to the purified antibody. Sera from six patients with SLE that reacted with both MPO and DNA were treated with DNase and showed a decrease in MPO binding activity compared with untreated samples. MPO binding activity was observed when CT-DNA was added to sera from SLE patients that initially reacted with DNA but not with MPO. These results suggest that the DNA contained within the antigen binding site of anti-DNA antibodies could bind to the highly cationic MPO used as substrate antigen in immunoassays, resulting in a false-positive test.

The life readiness program: a physical rehabilitation program for patients on hemodialysis

Patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) are typically sedentary and functionally limited as a consequence of their condition. The purpose of this study is to test the effect of a lifestyle physical rehabilitation program (The Life Readiness Program) on physical function in patients with ESRD undergoing HD. Physical function was measured by the Kidney Disease Quality of Life Short Form (KDQOL-SF) physical function score (range, 0 to 100). Eighty-two patients were randomly assigned to a 6-month rehabilitation program (intervention; n = 39) or to standard clinical management alone (control; n = 43). The groups were frequency matched by age, sex, ethnicity, and diabetes as the cause of ESRD. General linear modeling of the change in physical function score was used for multivariate analysis. Physical function scores were not different between groups at baseline. Change in physical function score increased significantly in the intervention group compared with the control group when data were adjusted for the matching variables and adequacy of dialysis (3.2, -3.6; P = 0.04). Additionally, the control group reported more problems with work or daily functions because of emotional problems (P: </= 0.05). In this brief 6-month intervention, The Life Readiness Program showed the therapeutic benefit of a lifestyle rehabilitation program on functional outcomes and health-related quality of life for patients with ESRD undergoing hemodialysis.

Target antigens for anti-neutrophil cytoplasmic autoantibodies (ANCA) are on the surface of primed and apoptotic but not unstimulated neutrophils

The reaction of ANCA with ANCA antigens on the surface of neutrophils may play a critical role in the pathogenesis of ANCA vasculitis. Therefore, an understanding of the circumstances that result in surface expression of these antigens is important for an understanding of pathogenic mechanisms. In this study we investigated the surface expression of ANCA antigens on quiescent, primed, and apoptotic neutrophils. ANCA antigens and other granule constituents were not detected on the surface of neutrophils in freshly heparinized blood. ANCA antigens were on the surface of neutrophils primed by in vitro incubation for 4 h and 8 h. These cells did not show evidence of apoptosis. After 24 h incubation, about 30% of the neutrophils were apoptotic, and ANCA antigens and other granule constituents were present on the surface of both apoptotic and non-apoptotic cells. Our data indicate that there are no ANCA antigens on the surface of quiescent neutrophils, but that they are on the surface of primed neutrophils before the cells become apoptotic, and remain on the surface of cells after they become apoptotic. Based on these observations, we hypothesize that ANCA can react in vivo with primed but not quiescent neutrophils. Previously published observations indicate that the interaction of ANCA with primed neutrophils results in neutrophil activation, which may be involved in the pathogenesis of ANCA vasculitis.

Parvovirus B19 DNA in kidney tissue of patients with focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) represents a clinicopathological syndrome with diverse causes. We examined the possibility that some cases of FSGS are associated with parvovirus B19 infection. We studied renal biopsy tissue from 40 patients, including those with idiopathic FSGS, collapsing FSGS, membranous nephropathy, and minimal change disease, as well as normal renal tissue removed at the time of nephrectomy from 4 patients. DNA was extracted from frozen blocks of kidney tissue and amplified using nested polymerase chain reaction. Parvovirus B19 DNA was amplified from 8 of 10 patients with idiopathic FSGS, 9 of 10 patients with collapsing FSGS, 6 of 10 patients with membranous nephropathy, 5 of 10 patients with minimal change disease, and 2 of 4 cancer nephrectomy samples. The prevalence of parvovirus B19 DNA was greater among patients with idiopathic FSGS and collapsing FSGS compared with patients with other diagnoses (P = 0.05). In situ hybridization studies using digoxigenin-labeled DNA probes failed to detect parvovirus B19 nucleic acid in any of the kidney tissue samples. These results suggest that parvovirus B19 DNA is commonly found in the kidneys of patients with a range of renal diagnoses, possibly representing latent DNA from past infection. The failure to localize parvovirus B19 nucleic acid within kidney argues against ongoing, high-level viral replication. Nevertheless, the increased prevalence of B19 DNA in patients with idiopathic FSGS and collapsing FSGS could indicate a pathogenic role for the virus in the cause of FSGS in certain patients.

ANCA antigens, proteinase 3 and myeloperoxidase, are not expressed in endothelial cells

BACKGROUND

One hypothesis for the pathogenesis of vasculitis associated with antineutrophil cytoplasmic autoantibodies (ANCAs) proposes that ANCAs bind to ANCA antigens, such as proteinase 3 (PR3) or myeloperoxidase (MPO), which are produced by endothelial cells and expressed on their surfaces. There are conflicting reports, however, on whether endothelial cells express the ANCA antigen PR3, and there are no reports on endothelial expression of MPO. The aim of this study was to determine the presence or absence of PR3 and MPO mRNA in both venous and arterial endothelial cells, employing standard reverse transcription-polymerase chain reaction (RT-PCR) techniques and also the quantitative and highly specific method, TaqMan PCR.

METHODS

RT-PCR (with 3 primer sets) and TaqMan PCR, a method for detecting low copy transcripts, were used to probe for PR3 and MPO transcripts in human endothelial cells from umbilical vein (HUVEC) and artery (HUAEC) and from lung microvascular (HLMVEC). Cells were treated with interferon-gamma (200 units/mL) or tumor necrosis factor-alpha (3 or 10 ng/mL) or both.

RESULTS

Transcripts for PR3 and/or MPO were not detected in HUVEC, HUAEC, and HLMVEC by standard RT-PCR. Analyses for PR3 protein confirmed that PR3 is not expressed in HUVEC. HUVEC and HUAEC were negative for PR3 and MPO by TaqMan PCR.

CONCLUSIONS

PR3 and MPO are not expressed in HUVEC, HUAEC, or HLMVEC. Endothelial cell presentation of endogenous PR3 and MPO antigens is not involved in the pathogenesis of ANCA-associated vasculitis. Alternative explanations need to be explored to determine the pathogenic effect of ANCAs.