Persistent T-cell activation and clinical correlations in patients with ANCA-associated systemic vasculitis

Activity of granulomatosis with polyangiitis and its correlation with mTOR phosphoproteomics in neutrophils

Introduction

Granulomatosis with polyangiitis (GPA) is a small vessel vasculitis with a complex pathomechanism. Organ damage in GPA is also mediated by extracellular trap formation (NETosis). We analyzed the functional status of phosphoproteins modulating NETosis in neutrophils by the mammalian target of rapamycin (mTOR) pathway in GPA along with NETosis biomarkers.

Methods

Phosphoproteins levels measured in isolated neutrophils from 42 patients with GPA (exacerbation n=21; remission n=21) and 21 healthy controls were compared to serum biomarkers of the disease.

Results

Neutrophils in active disease manifested lowered levels of phosphorylated mTOR(Ser2448), PTEN(Ser380) and ULK1(Ser555), whereas phosphorylated GSK-3α/β(Ser21/Ser9) was elevated. Exacerbation of GPA was characterized by elevated neutrophil dsDNA in serum, circulating mitochondrial DNA, and DNA-MPO complexes. A significant negative correlation between mTOR or PTEN phosphoproteins and biomarkers of GPA activity was also present, reflecting the clinical activity score of GPA. Positive correlations between phosphorylated GSK-3 α/β and circulating mtDNA, DNA-MPO complexes, neutrophil-released dsDNA, or circulating proteins were also significant. Increased serum levels of IGFBP-2, TFF-3, CD147, and CHI3L1 accompanied GPA exacerbation, whereas DPP-IV levels were the lowest in active GPA. Using a principal component analysis basigin, PTEN and mTOR had the highest loadings on the discrimination function, allowing classification between active, remission, and control subjects with 98% performance.

Conclusions

We present evidence that inhibited mTOR signaling accompanies NETosis in patients with GPA. The functional status of phosphoproteins suggests simultaneous activation of NETosis and autophagy. These results give rise to the study of autophagy as a mechanism underlying granuloma formation in GPA.

Transcriptional and Clonal Characterization of Cytotoxic T Cells in Crescentic Glomerulonephritis

SIGNIFICANCE STATEMENT

T-cell infiltration is a hallmark of crescentic GN (cGN), often caused by ANCA-associated vasculitis. Pathogenic T-cell subsets, their clonality, and downstream effector mechanisms leading to kidney injury remain to be fully elucidated. Single-cell RNA sequencing and T-cell receptor sequencing revealed activated, clonally expanded cytotoxic CD4 + and CD8 + T cells in kidneys from patients with ANCA-associated cGN. In experimental cGN, kidney-infiltrating CD8 + T cells expressed the cytotoxic molecule, granzyme B (GzmB), which induced apoptosis in renal tissue cells by activation of procaspase-3, and aggravated disease pathology. These findings describe a pathogenic function of (clonally expanded) cytotoxic T cells in cGN and identify GzmB as a mediator and potential therapeutic target in immune-mediated kidney disease.

BACKGROUND

Crescentic GN (cGN) is an aggressive form of immune-mediated kidney disease that is an important cause of end stage renal failure. Antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitis is a common cause. T cells infiltrate the kidney in cGN, but their precise role in autoimmunity is not known.

METHODS

Combined single-cell RNA sequencing and single-cell T-cell receptor sequencing were conducted on CD3 + T cells isolated from renal biopsies and blood of patients with ANCA-associated cGN and from kidneys of mice with experimental cGN. Functional and histopathological analyses were performed with Cd8a-/- and GzmB-/- mice.

RESULTS

Single-cell analyses identified activated, clonally expanded CD8 + and CD4 + T cells with a cytotoxic gene expression profile in the kidneys of patients with ANCA-associated cGN. Clonally expanded CD8 + T cells expressed the cytotoxic molecule, granzyme B (GzmB), in the mouse model of cGN. Deficiency of CD8 + T cells or GzmB ameliorated the course of cGN. CD8 + T cells promoted macrophage infiltration and GzmB activated procaspase-3 in renal tissue cells, thereby increasing kidney injury.

CONCLUSIONS

Clonally expanded cytotoxic T cells have a pathogenic function in immune-mediated kidney disease.

Unraveling the identity of FoxP3+ regulatory T cells in Granulomatosis with Polyangiitis patients

Human CD4⁺FoxP3⁺T-cells are heterogeneous in function and include not only suppressive cells (Tregs), but also effector cells that transiently express FoxP3 upon activation. Previous studies in Granulomatosis with Polyangiitis (GPA-)patients have demonstrated an increase in FoxP3⁺T-cells with impaired suppressive capacity and an increase in Th17 cells. We hypothesized that the increase in FoxP3⁺T-cells results from an increase in non-suppressive effector-like cells. The frequency of circulating CD4⁺FoxP3⁺T-cell subsets were determined by flow cytometry in 46 GPA-patients in remission and 22 matched healthy controls (HCs). Expression levels of FoxP3 and CD45RO were used to distinguish between CD45RO⁻FoxP3^low resting Tregs (rTreg), CD45RO⁺FoxP3^high activated Tregs (aTreg) and CD45RO⁺FoxP3^low proinflammatory non-suppressive T-cells (nonTreg). Intracellular expression of IFNγ, IL-17, and IL-21 was compared within these subsets. We found a significant increase in the frequency of nonTreg cells in GPA-patients as compared with HCs. Importantly, within the nonTreg subset, antineutrophil cytoplasmic autoantibody (ANCA-)positive patients demonstrated a significantly higher percentage of IL-17+ and IL-21+ cells when compared with ANCA-negative patients and HCs. Moreover, expanded nonTregs from ANCA-positive patients induced excessive proliferation of responder cells in vitro and exhibited higher IL-21 production. Production of IL-17 and IL-21 in non-suppressive FoxP3⁺T-cells may point toward a pathogenic role in ANCA formation.

Could Lymphocyte Profiling be Useful to Diagnose Systemic Autoimmune Diseases?

Considering the implications of B, T, and natural killer (NK) cells in the pathophysiology of systemic autoimmune diseases, the assessment of their distribution in the blood could be helpful for physicians in the complex process of determining a precise diagnosis. In primary Sjögren's syndrome, transitional and active naive B cells are increased and memory B cells are decreased compared to healthy controls and other systemic diseases. However, their utility to improve the accuracy of classification criteria has not been proven. In early untreated rheumatoid arthritis, proportions of regulatory T cells are constantly reduced, but other patterns are difficult to determine given the heterogeneity of published studies. In systemic lupus erythematosus, the lack of studies using large cohorts of patients and the diversity of the possible pathological mechanisms involved are also important impediments. Nevertheless, transitional B cell and plasma cell proportions are increased in most of the studies, the CD4/CD8 ratio is decreased, and the number of NK cells is reduced. Despite the low number of studies, anomalies of lymphocyte subset distribution was also described in ANCA-associated vasculitis, systemic scleroderma, and myositis. For now, flow cytometric analysis of lymphocyte subsets has focused mainly on specific subpopulations and is more useful for basic and translational research than for diagnostics in clinical practice. However, new modern methods such as mass cytometry and bioinformatics analyses may offer the possibility to simultaneously account for the relative proportions of multiple lymphocyte subsets and define a global profile in homogeneous groups of patients. The years to come will certainly incorporate such global lymphocyte profiling in reclassification of systemic autoimmune diseases.

CD4 cell count and CD4/CD8 ratio increase during rituximab maintenance in granulomatosis with polyangiitis patients

Introduction

Rituximab (RTX) is a B cell-depleting agent approved for the treatment of granulomatosis with polyangiitis (GPA). RTX reduces antibody producing precursor plasma cells and inhibits B and T cells interaction. Infections related to T cell immunodeficiency are not infrequent during RTX treatment. Our study investigated CD4 cell count and CD4/CD8 ratio in GPA patients during the first two years of long-term RTX treatment.

Methods

A single centre cohort study of 35 patients who received median total cumulative dose of cyclophosphamide (CYC) of 15 g and were treated with RTX 2 g followed by retreatment with either 2 g once annually or 1 g biannually. Serum levels of total immunoglobulin (Ig) and lymphocytes subsets were recorded at RTX initiation and at 3, 6, 12, 18 and 24 months. Low CD4 count and inverted CD4/CD8 ratio were defined as CD4 < 0.3 × 10⁹/l and ratio < 1.

Results

The CD4 cell count and CD4/CD8 ratio decreased slightly following the initial RTX treatment and then increased gradually during maintenance treatment. While the proportion of patients with low CD4 cell count decreased from 43% at baseline to 18% at 24 months, the ratio remained inverted in 40%. Oral daily prednisolone dose at baseline, CYC exposure and the maintenance regimen did not influence the CD4 cell count and ratio. Being older (p = 0.012) and having a higher CRP (p = 0.044) and ESR (p = 0.024) at baseline significantly increased the risk of inverted CD4/CD8 ratio at 24 months. Inverted ratio at baseline associated with lower total Ig levels during the study.

Conclusions

Overall, the CD4 and CD4/CD8 ratio increased during maintenance RTX therapy in GPA with no discernible impact of other immunosuppressive therapy. However the increase in CD4 was not followed by an increase in the CD4/CD8 ratio, especially in older patients. Inverted CD4/CD8 ratio associated with lower Ig levels, suggesting a more profound B cell depleting effect of RTX with a relative increase in CD8+ lymphocytes.

IL-17 production by CSF lymphocytes as a biomarker for cerebral vasculitis

OBJECTIVE

To explore the possibility of using interleukin-17 (IL-17) production by CD4+ T cells in the CSF as a potential biomarker for cerebral vasculitis in stroke patients.

METHODS

In this consecutive case study, we performed prospective analysis of CSF and blood in patients admitted to a university medical center with symptoms of stroke and suspected cerebral vasculitis. Flow cytometry was performed for intracellular detection of inflammatory cytokines in peripheral blood lymphocytes and expanded T cells from CSF.

RESULTS

CSF CD4+ lymphocytes from patients with cerebral vasculitis showed significantly higher levels of the proinflammatory cytokine IL-17 compared to patients with stroke not due to vasculitis or with other, noninflammatory neurologic diseases. There was no difference in the production of interferon-γ in the CSF and no overall differences in the relative frequencies of peripheral immune cells.

CONCLUSIONS

Intracellular IL-17 in CSF cells is potentially useful in discriminating cerebral vasculitis as a rare cause in patients presenting with ischemic stroke.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that an increased proportion of IL-17-producing CD4+ cells in CSF of patients presenting with stroke symptoms is indicative of cerebral vasculitis (sensitivity 73%, 95% confidence interval [CI] 39-94%; specificity 100%, 95% CI 74%-100%).

Rituximab use in patients with ANCA-associated vasculitis: clinical efficacy and impact on immunological parameters

Rituximab (RTX) was reported effective in ANCA-associated vasculitis (AAV). We aimed to evaluate clinical efficacy of RTX in AAV along with its impact on immunological parameters. Eighteen RTX-treated AAV patients (M/F 11/7; median age 37.5; 15× PR3-ANCA, 3× MPO-ANCA; 16× relapsing/refractory, 2× first-line therapy) were enrolled. Clinical response, ANCA, total serum IgG levels and cellular immunity parameters were examined. The patients were followed up (FU) for a median of 26 months (range 3-82, 15 for ≥6 months). All patients achieved B cell depletion (lasting 3-24 months). No significant increase was noted in T cell or NK cell subpopulations. At 6 months, partial remission was achieved in 5/15 patients (33 %) and complete in 8 (53 %). The median prednisone dose (30..10 mg/d) and ANCA levels (17.2..2.7 IU/mL) decreased (p < 0.01). RTX retreatment was used in nine (8× pre-emptive, 1× relapse). Six patients relapsed (none of the pre-emptively treated). Three patients died of infection. IgG levels at 3 months decreased compared to baseline (9.0 vs 5.7 g/L, p < 0.01). Higher percentage of HLA-DR+CD3+ cells and lower percentage of CD4+CD45RA+ naive T cells persisted during FU. IFN-γ production increased at 6 months compared to baseline (27.3 vs 41.5 %). No significant change was noted in the intracellular IL-10 and IL-12 production. RTX helped to lower the glucocorticosteroids dose and withdraw cytotoxic drugs in most AAV patients. Hypogammaglobulinaemia was common but well tolerated. Peripheral circulating T cells remained activated despite B cell depletion.

The immunopathology of ANCA-associated vasculitis

The small-vessel vasculitides are a group of disorders characterised by variable patterns of small blood vessel inflammation producing a markedly heterogeneous clinical phenotype. While any vessel in any organ may be involved, distinct but often overlapping sets of clinical features have allowed the description of three subtypes associated with the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCA), namely granulomatosis with polyangiitis (GPA, formerly known as Wegener’s Granulomatosis), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (eGPA, formerly known as Churg-Strauss syndrome). Together, these conditions are called the ANCA-associated vasculitidies (AAV). Both formal nomenclature and classification criteria for the syndromes have changed repeatedly since their description over 100 years ago and may conceivably do so again following recent reports showing distinct genetic associations of patients with detectable ANCA of distinct specificities. ANCA are not only useful in classifying the syndromes but substantial evidence implicates them in driving disease pathogenesis although the mechanism by which they develop and tolerance is broken remains controversial. Advances in our understanding of the pathogenesis of the syndromes have been accompanied by some progress in treatment, although much remains to be done to improve the chronic morbidity associated with the immunosuppression required for disease control.

Signal tranducers and activators of transcription: expression and function in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune small vessel vasculitis. Despite the role of autoantibodies, T cells play an essential role in pathogenesis and are abnormal in AAV. Signal transducers and activators of transcription (STAT) affect immunoregulation and T-cell homeostasis. Therefore, the present study examined the ex vivo basal expression of the activated forms of STAT5 [phosphorylated (p)STAT5] and STAT3 (pSTAT3) in AAV and analyzed the function of two signaling pathways linked to these transcription factors. In total, 31 patients with AAV and 16 age-matched healthy controls (HCs) were enrolled. CD3+ T cells from peripheral blood were analyzed directly ex vivo by a fluorescence-activated cell sorter for basal expression of pSTAT5 and pSTAT3. Expression was also analyzed in T cells following short-term stimulation with interleukin (IL)-2 or -10. The basal expression of pSTAT5/3 in T cells was similar to AAV patients and HC. Following stimulation with IL-2 or -10, expression of pSTAT5/3 increased in AAV subjects compared with HC. Basal expression of pSTAT3 correlated with the relapse rate in AAV. In conclusion, STAT3 and STAT5 mediated signaling pathways were functionally intact in AAV patients and exhibited hyper-responsiveness to IL-2 and -10 stimuli. Thus, T-cell abnormalities in AAV are not promoted by an altered basal expression of pSTAT5/3 or dysfunction of the IL-2/-10 signaling pathways, in which STAT5/3 are essential.

Abnormal expression pattern of the IL-2 receptor β-chain on CD4+ T cells in ANCA-associated vasculitis

BACKGROUND/AIM

ANCA-associated vasculitis (AAV) is a small-vessel vasculitis of autoimmune origin. In addition to autoantibodies, T cells have a pivotal pathophysiological role in this disease. T-cell homeostasis and immune tolerance critically depend on IL-2 and its receptor expressed by T cells. In this study, we investigated the IL-2 receptor (IL-2r) expression on CD4(+) T cells in AAV.

METHODS

Thirty patients with AAV and 15 age-matched healthy controls (HC) were enrolled. T cells from peripheral blood were analysed by flow cytometry for expression of the IL-2r α - and β-chain.

RESULTS

The IL-2r α-chain was overexpressed in AAV as compared to HC (36 ± 16% versus 20 ± 9%, P < 0.005). The IL-2r-β-chain expression was significantly reduced on CD25(+) CD4(+) T-cells and CD4(+)CD25(+)FoxP3(pos) regulatory T-cells (Tregs; AAV versus HC: 48 ± 14% versus 62 ± 9%, P = 0.002 and 38 ± 18% versus 68 ± 5%, P = 0.002). Low β -chain expression in AAV was associated with relapsing disease and systemic vasculitis with renal involvement.

CONCLUSION

The IL-2r expression pattern is abnormal in AAV. To our knowledge, we are the first to show that the β -chain expression is drastically diminished on T cells in AAV and related to a less favorable disease course. Given the indispensable function of the β -chain in IL-2 signaling of T cells, diminished expression may contribute to disturbed immune homeostasis in AAV.

Increased frequency of CCR4+ and CCR6+ memory T-cells including CCR7+CD45RAmed very early memory cells in granulomatosis with polyangiitis (Wegener's)

INTRODUCTION

Chemokine receptors play an important role in mediating the recruitment of T cells to inflammatory sites. Previously, small proportions of circulating Th1-type CCR5+ and Th2-type CCR3+ cells have been shown in granulomatosis with polyangiitis (GPA). Wondering to what extent CCR4 and CCR6 expression could also be implicated in T cell recruitment to inflamed sites in GPA, we investigated the expression of CCR4 and CCR6 on T cells and its association with T cell diversity and polarization.

METHODS

Multicolor flow cytometry was used to analyze CCR4, CCR6, and intracellular cytokine expression of T cells from whole blood of GPA-patients (n = 26) and healthy controls (n = 20). CCR7 and CD45RA were included for phenotypic characterization.

RESULTS

We found a significant increase in the percentages of circulating CCR4+ and CCR6+ cells within the total CD4+ T cell population in GPA. In contrast, there was no difference in the percentages of CD8+CCR4+ and CD8+CCR6+ T cells between GPA and healthy controls. CCR4 and CCR6 expression was largely confined to central (TCM) and effector memory T cells (TEM, TEMRA). A significant increase in the frequency of CCR4+ and CCR6+ TEMRA and CCR6+ TCM was shown in GPA. Of note, we could dissect CCR4 and CCR6 expressing CCR7+CD45RAmed very early memory T cells (TVEM) from genuine CCR7+CD45RAhigh naïve T cells lacking CCR4 and CCR6 expression for peripheral tissue-migration within the CCR7+CD45RA+ compartment. The frequencies of CCR4+ and CCR6+ TVEM were also significantly increased in GPA. An increased percentage of IL-17+ and IL-22+ cells was detected in the CCR6+ cell subsets and IL-4+ cells in the CRR4+ cell subset when compared with CD4+ cells lacking CCR4 and CCR6 expression.

CONCLUSIONS

Increased frequencies of circulating CCR4+ and CCR6+ memory T cell subsets including hitherto unreported TVEM suggest persistent T cell activation with the accumulation of CCR4+ and CCR6+ cells in GPA. CCR4 and CCR6 could be involved in the recruitment of T cells including cytokine-producing subsets to inflamed sites in GPA.

Aberrant expression of the negative costimulator PD-1 on T cells in granulomatosis with polyangiitis

OBJECTIVE

Persistent T-cell activation is frequently observed in granulomatosis with polyangiitis (GPA, formerly known as Wegener's granulomatosis). T-cell activation is usually balanced by negative costimulatory molecules. The negative costimulator programmed death receptor-1 (PD-1) and its relevance to T-cell immunity have not been studied so far in GPA. Thus it is the aim of the study to characterize the role of PD-1 in GPA.

METHODS

Thirty-two patients suffering from GPA and 19 age-matched healthy controls (HCs) were enrolled. T-lymphocyte subsets from peripheral blood were analysed by flow cytometry for the expression of PD-1. The frequency of memory T cells and T cells producing pro-inflammatory cytokines was determined. Renal biopsies from GPA patients were stained for CD3 and PD-1.

RESULTS

PD-1 expression was increased on T-helper cells (Th cells) from GPA patients as compared with HCs. In addition, parameters of persistent T-cell activation and production of pro-inflammatory cytokines were positively associated with numbers of PD-1(+) Th cells in patients but not in HCs. Latent infection with CMV seemed to enhance PD-1 expression on CD4(+) and CD4(+)CD25(-) T cells. Interestingly, expression of PD-1 on CD4(+)CD25(+)T cells was inversely correlated with relapse rate. Importantly, lesional T cells were mostly lacking PD-1.

CONCLUSIONS

The expression of the negative costimulator PD-1 is altered in GPA and might counterbalance persistent T-cell activation.

T-helper cells as new players in ANCA-associated vasculitides

In anti-neutrophil cytoplasmic autoantibody-associated vasculitides (AAV), several observations support a key role of T-helper cells (CD4(+) T cells) in disease pathophysiology. An expanded population of effector memory CD4(+) T cells in AAV patients may contribute to tissue injury and disease progression. In addition, functional impairment of regulatory T cells (T(Regs)) is reported in AAV patients. A fraction of T(Regs) have the capacity to differentiate into Th17 cells in the context of a proinflammatory environment. Therefore, nonfunctionality of T(Regs) described in AAV patients may be caused by their conversion into IL-17-producing cells that may contribute to granulomatous vasculitis. Further investigations directed at the plasticity of T(Regs) in AAV patients are warranted.

Patients with Wegener's granulomatosis demonstrate a relative deficiency and functional impairment of T-regulatory cells

An increased proportion of CD4(+) CD25(+) T cells has been reported in Wegener's granulomatosis (WG) and may represent an accumulation of regulatory T cells (Treg). CD25 is also expressed on recently activated effector T cells. We have determined the relative proportion of these subsets in a large patient cohort. The fraction of Treg in peripheral blood mononuclear cells from patients and healthy controls was determined by assessment of Foxp3 expression on CD4(+) CD25(+) T cells. The functional activity of Treg was determined by their ability to suppress proliferation and cytokine production in response to proteinase-3. Although WG patients demonstrated an increased fraction of CD4(+) CD25(+) T cells, the percentage of Foxp3-positive cells was decreased. In addition, the percentage of Treg was inversely related to the rate of disease relapse. CD4(+) CD25(hi) T cells were able to suppress T-cell proliferation to proteinase-3 in healthy controls and anti-neutrophil cytoplasm antibody (ANCA)- negative patients (at time of sampling) but not in ANCA-positive patients. In patients with active disease, an increased proportion of CD4(+) Foxp3(+) cells was associated with a more rapid disease remission. Patients with WG demonstrate abnormalities in the number and function of Treg and this is most pronounced in those with most active disease. This information is of value in understanding the pathogenesis and potential treatment of this disease.

T cells in ANCA-associated vasculitis: what can we learn from lesional versus circulating T cells?

Anti-neutrophil cytoplasmic antibody (ANCA) - associated vasculitis (AAV) is a life-threatening autoimmune disease characterized by an antibody-mediated glomerulonephritis and necrotizing vasculitis. Apart from antibodies, T cells are also involved in disease pathogenesis. This review stresses the hallmarks of T cell-mediated pathology in AAV and highlights the characteristics of lesional and circulating T cells in the immune response in AAV. Circulating effector T-cell populations are expanded and are in a persistent state of activation. Circulating regulatory T-cell subsets are less well characterized but seem to be impaired in function. Lesional effector T cells are present in granulomas, vasculitic lesions, and nephritis. Lesional T cells usually show pro-inflammatory properties and promote granuloma formation. Apart from T cells, dendritic cells are abundantly present at the sites of inflammation and locally orchestrate the immune response. Targeting the above-mentioned T cell-mediated disease mechanisms will potentially provide powerful therapeutic tools for AAV.

Anti-neutrophil cytoplasmic antibody pathogenesis in small-vessel vasculitis: an update

Vasculitides associated with serum positivity for anti-neutrophil cytoplasmic antibodies (ANCAs) that affect small- to medium-sized vessels are commonly known as ANCA-associated vasculitis (AAV) and include Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. Evidence derived from both in vitro studies and recent animal models points to a pathogenic role of ANCAs in AAV. In 2002, the first in vivo breakthrough in the pathogenesis of ANCAs showed that mouse ANCAs against myeloperoxidase (MPO) led to intrinsic pauci-immune renal vasculitis in mice. In 2004, a report using both in vitro and in vivo studies proposed that proteinase 3 (PR3)-directed autoimmunity involved the complementary peptide of PR3 (cPR3), which is encoded by the antisense strand of the PR3 gene. The last breakthrough came in October 2008 with a previously undescribed molecular explanation for the origin and development of injury in pauci-immune renal vasculitis, with potential clinical implications. This report showed that infection by fimbriated bacteria may trigger cross-reactive autoimmunity to a previously characterized ANCA antigen, lysosomal membrane protein-2, which is contained in the same vesicles that harbor MPO and PR3. Infection by fimbriated bacteria resulted in the production of autoantibodies, which activated neutrophils and killed human microvascular endothelium in vitro and caused renal vasculitis in rats. Although the evidence for a pathogenic role of ANCAs, mainly MPO-ANCAs, is striking, various questions remain unanswered. Understanding the key pathogenic mechanisms of AAV may provide a safer, more rational therapeutic approach than the traditional (ie, corticosteroids and immunosuppressants) treatment strategy.

Intracellular cytokine production in ANCA-associated vasculitis: low levels of interleukin-10 in remission are associated with a higher relapse rate in the long-term follow-up

BACKGROUND AND AIMS

Dysregulation of cell-mediated immune response likely plays a role in the pathogenesis of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV), but it has not yet been fully established. The aim of this study was to assess the intracellular cytokine production in patients with AAV at different stages of the disease, in particular, in relation to the long-term prognosis.

METHODS

We included 69 patients with AAV and 24 healthy controls. Using flow cytometry, the following intracellular cytokines (IC) were measured in all patients: interferon-gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), interleukin-2 and interleukin-4 in CD3+T cells and interleukin-10 (IL-10) and interleukin 12 (IL-12) in monocytes. Patients were then prospectively followed for a median of 43 months and cytokine production was related to the long-term prognosis.

RESULTS

When compared to healthy controls, increased IL-12 production was observed in AAV patients, both active (p<0.01) and in remission (p<0.05). In remission, increased IFN-gamma production was also found (p<0.01). IL-10 production was higher in active patients than in patients in remission (p<0.05) but did not differ from controls. Patients in remission who developed a relapse during follow-up had significantly lower IL-10 production than those without relapse (p<0.01). Results of this prospective study of IC production in AAV confirm findings of previous studies measuring circulating cytokine levels.

CONCLUSIONS

Activation of the immune system in AAV patients is noticeable even in remission. Patients with AAV display increased IL-12 production, which seems to be counterbalanced by IL-10. Low IL-10 levels in remission are associated with a higher relapse rate in the long-term follow-up.

[Progress in pathogenesis and therapy of vasculitis syndrome]

Since antineutrophil cytoplasmic autoantibody (ANCA) was found, the researches in the pathogenesis of vasculitis syndrome have been developing. Proinflammatory cytokines including tumor necrosis factor-alpha are induced by certain infections, by which ANCA that binds to granule components of cytoplasm adhesions to endothelial cells. These endothelial cells produce proteolytic enzymes and oxygen radicals, which leads to vasculitis. It might be contributed in the production of ANCA that bacterial organisms are mimicry to the peptide sequences of granule components. The multicentric randomized clinical trials undertaken by the European Vasculitis Study Group (EUVAS) optimized that cyclophosphamide-corticosteroid combination therapy was useful to ANCA-associated vasculitis. It is increasing evidences that biologics are useful to ANCA-associated vasculitis, although it is necessary to take care of severe adverse effects.

Imatinib mesylate, a new kid on the block for the treatment of anti-neutrophil cytoplasmic autoantibodies-associated vasculitis?

Persistent T cell activation is a common finding in anti-neutrophil cytoplasmic autoantibodies (ANCA)-associated systemic vasculitis (AAV) patients. Because imatinib, a selective inhibitor of the ABL, ARG, PDGFR and c-KIT tyrosine kinases, inhibits T cell activation, this study was conducted to evaluate the potential use of imatinib for the treatment AAV patients refractory to conventional therapy. In particular, we investigated the inhibition of T cell activation by this drug and its efficacy on activated T cells from anti-neutrophil cytoplasmic autoantibodies (ANCA)-associated systemic vasculitides (AASV) patients. T cell stimulation has been induced by anti-CD3/anti-CD28 antibodies or by phorbol myristate acetate (PMA)/ionomycin. T cell proliferation was analysed by tritiumthymidine incorporation. Cell cycle progression was determined by propidium iodide staining using fluorescence activated cell sorter (FACS) analysis and by RNAse protection assay (RPA). Cytokine levels were assessed by enzyme-linked immunosorbent assay. T cell proliferation was inhibited significantly by imatinib, due most probably to cell cycle arrest in the G1-phase. This was paralleled by inhibition in the expression of cyclin-dependent kinases 1 and 2 mRNA. The expression of CD25 in naive and memory T cells was decreased significantly by imatinib in activated T cells. Similarly, conversion from naive to memory T cells after T cell activation was impaired by imatinib. Imatinib did not influence interleukin-2 and tumour necrosis factor-alpha production but increased interferon-gamma production. These observed effects of imatinib were similar in T cells from AASV patients and from healthy individuals. Imatinib might be an alternative therapeutical option for AASV patients refractory to conventional therapy.

CD4-Positive Effector Memory T Cells Participate in Disease Expression in ANCA-Associated Vasculitis

Although the cause of ANCA-associated vasculitis (AAV) remains undetermined, the presence of lymphocytic infiltrates in inflammatory lesions of patients suggests that vascular damage is immune mediated. Studies over the past decade have implicated a role for T cells in the pathogenesis of AAV as altered T cell phenotype has been observed in this disorder. The distribution of T cell subpopulations has been analyzed most intensely in Wegener's granulomatosis (WG), where an expanded population of circulating CD4(+) effector memory T cells (CD4(+)T(EM)) was demonstrated. CD4(+)T(EM) cells play a major role in the pathogenesis of several autoimmune diseases. Specific suppression of CD4(+)T(EM) cells inhibits delayed-type hypersensitivity (DTH) and has therapeutic potential in autoimmune disease. Thus, CD4(+)T(EM) cells may act as inducers of tissue injury and participate in the development of AAV. Therapies that target CD4(+)T(EM), without impairing the activity of other lymphocyte subsets, may hold therapeutic promise for AAV.

Antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitis

PURPOSE OF REVIEW

This review focuses on recent advances in the diagnosis, pathogenesis and treatment of antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitis.

RECENT FINDINGS

Antineutrophil cytoplasmic autoantibodies are closely associated with Wegener's granulomatosis and microscopic polyangiitis. Within the Churg-Strauss syndrome, antineutrophil cytoplasmic autoantibodies, mostly directed towards myeloperoxidase, characterize patients with glomerulonephritis and small-vessel vasculitis. There is increasing evidence that myeloperoxidase-antineutrophil cytoplasmic autoantibodies are directly involved in the pathogenesis of necrotizing vasculitis. This is less clear for proteinase 3-antineutrophil cytoplasmic autoantibodies, markers for Wegener's granulomatosis. With respect to proteinase 3-antineutrophil cytoplasmic autoantibodies, complementary proteinase 3, a peptide translated from the antisense DNA strand of proteinase 3 and homologous to several microbial peptides, may be involved in induction of proteinase 3-antineutrophil cytoplasmic autoantibodies. Currently, various controlled trials have been initiated. Methotrexate has been shown to be effective for induction of remission in locoregional Wegener's granulomatosis. Other trials are underway.

SUMMARY

Apart from its diagnostic potential, antineutrophil cytoplasmic autoantibodies, particularly myeloperoxidase-antineutrophil cytoplasmic autoantibodies, are directly involved in the pathogenesis of the associated vasculitides. New treatment modalities, supposedly more efficacious and less toxic than daily oral cyclophosphamide, are being tested in randomized controlled trials.

In vivo effects of cyclic administration of 15-deoxyspergualin on leucocyte function in patients with Wegener's granulomatosis

15-Deoxyspergualin (DSG) is an alternative treatment modality for Wegener's granulomatosis (WG) patients refractory to conventional treatment. Nevertheless, it is unclear how DSG modulates disease activity in these patients. This study was conducted to investigate which parameters of adaptive and acquired immunity were influenced during two subsequent cycles of DSG treatment. Emphasis was put upon T cell and monocyte activation, neutrophil function and surface expression of proteinase-3 (PR-3). Anti-CD3/anti-CD28 and interleukin (IL)-15/IL-7-mediated T cell proliferation were assessed by fluorescence activated cell sorter (FACS) analysis using carboxyfluorescein succinimidyl ester (CSFE) labelling. Interferon (IFN)-gamma and IL-10 production were determined in the supernatants of these cultures by enzyme-linked immunosorbent assay. Monocyte activation was assessed in lipopolysaccharide (LPS)-stimulated whole blood, using tumour necrosis factor (TNF)-alpha as read-out. Neutrophil function was determined by measuring oxidative burst, chemotaxis and phagocytosis. T cell activation markers and PR3 expression were measured by FACS. All parameters were determined directly before and after each DSG cycle. Anti-CD3/anti-CD28-mediated T cell proliferation was reduced directly after DSG treatment. Directly before a subsequent cycle of DSG was started, T cell proliferation was increased. Similar findings were observed for IFN-gamma and IL-10 production by T cells. DSG did not influence IL-15/IL-7-mediated T cell proliferation. LPS-mediated TNF-alpha production was also impaired directly after DSG treatment. No influence on T cell activation markers, neutrophil function and surface PR-3 expression was observed in peripheral blood of these patients. Our data demonstrate that DSG influences T cell and monocyte activation in a reversible fashion. Although DSG causes neutropenia in these patients, it does not influence neutrophil function.

Functional defect of circulating regulatory CD4+ T cells in patients with Wegener's granulomatosis in remission

OBJECTIVE

Accumulating data support the role of regulatory T cells, a subset of CD4+ T cells that expresses CD25(high) and the transcription factor forkhead box P3 (FoxP3), in controlling and preventing autoimmunity. In Wegener's granulomatosis (WG), an autoimmune vasculitis, up-regulation of CD25 on circulating CD4+ T cells has been observed, even in patients in remission. The objective of this study was to test whether the frequency and/or function of Treg cells from WG patients in remission are disturbed.

METHODS

Peripheral blood mononuclear cells were freshly isolated from 52 WG patients in remission and from 27 age- and sex-matched healthy control subjects. The proportion of circulating Treg cells was assessed by flow cytometry using CD4, CD25, FoxP3, and CD45RO markers. Anergy and suppressive function of CD25(high),CD4+ T cells were determined using polyclonal stimulants and coculture assay in 10 WG patients in remission and in 10 age- and sex-matched healthy controls.

RESULTS

In WG patients, a significant increase was observed in the percentage of circulating CD25(high),CD4+ and CD25(low),CD4+ T cells, whereas CD25-,CD4+ T cells were decreased, as compared with healthy controls. Among circulating CD4+ T cells, an expanded percentage of Treg cells (CD25(high),FoxP3+) with memory phenotype was present in WG patients. However, when the suppressive function of CD25(high),CD4+ T cells was tested, CD25(high),CD4+ T cells from WG patients showed diminished or absent suppression of responder T cell proliferation. The impaired suppression was not due to responder cell resistance (as shown by crisscross experiments with T cells from healthy controls) or altered survival of Treg cells.

CONCLUSION

These data indicate that WG patients in remission have an expanded proportion of Treg cells that are functionally defective. This observation may be relevant to the development and relapsing course of this autoimmune vasculitis.