Neutrophil myeloperoxidase harbors distinct site-specific peculiarities in its glycosylation.

Anti-neutrophil cytoplasmic autoantibodies (ANCAs) are directed against lysosomal components of neutrophils. ANCAs directed to proteinase 3 and myeloperoxidase (MPO) in particular are associated with distinct forms of small vessel vasculitides. MPO is an abundant neutrophil-derived heme protein that is part of the antimicrobial defense system. The protein is typically present in the azurophilic granules of neutrophils, but a large portion may also enter the extracellular space. It remains unclear why MPO is frequently the target of antibody-mediated autoimmune responses. MPO is a homodimeric glycoprotein, posttranslationally modified with complex sugars at specific sites. Glycosylation can strongly influence protein function, affecting its folding, receptor interaction, and backbone accessibility. MPO potentially can be heavily modified as it harbors 5 putative N-glycosylation sites (10 in the mature dimer). Although considered important for MPO structure and function, the full scope and relative abundance of the glycans attached to MPO is unknown. Here, combining bottom-up glycoproteomics and native MS approaches, we structurally characterized MPO from neutrophils of healthy human donors. We quantified the relative occupancy levels of the glycans at each of the five sites and observed complex heterogeneity and site-specific glycosylation. In particular, we detected glycosylation phenotypes uncommon for glycoproteins in the extracellular space, such as a high abundance of phosphorylated high-mannose species and severely truncated small glycans having the size of paucimannose or smaller. We hypothesize that the atypical glycosylation pattern found on MPO might contribute to its specific processing and presentation as a self-antigen by antigen-presenting cells.

Effect of age and sex on immune checkpoint expression and kinetics in human T cells.

BACKGROUND: Immune checkpoints are crucial molecules in maintaining a proper immune balance. Even though age and sex are known to have effects on the immune system, the interplay between age, sex and immune checkpoint expression by T cells is not known. The aim of this study was to determine whether age and sex affect immune checkpoint expression by T cells and if age and sex affect the kinetics of immune checkpoint expression following ex vivo stimulation. In this study, whole blood samples of 20 healthy young adults (YA, 9 males and 11 females) and 20 healthy older adults (OA, 9 males and 11 females) were stained for lymphocyte lineage markers and immune checkpoints and frequencies of CD28+, PD-1+, VISTA+ and CD40L+ T cells were determined. Immune checkpoint expression kinetics were studied following ex vivo anti-CD3/anti-CD28 stimulation of T cells from young and older healthy adults. RESULTS: We report an age-associated increase of CD40L + CD4+ and CD40L + CD8+ T-cell frequencies, whereas CD40+ B-cell frequencies were decreased in older adults, suggesting modulation of the CD40L-CD40 interaction with age. Immune checkpoint expression kinetics revealed differences in magnitude between CD4+ and CD8+ T cells independent of age and sex. Further analysis of CD4+ T-cell subsets revealed an age-associated decrease of especially PD-1 + CD4+ memory T cells which tracked with the female sex. CONCLUSION: Collectively, our results demonstrate that both age and sex modulate expression of immune checkpoints by human T cells. These findings may have implications for optimising vaccination and immune checkpoint immunotherapy and move the field towards precision medicine in the management of older patient groups.

Clinical outcome in anti-neutrophil cytoplasmic antibody-associated vasculitis and gene variants of 11ß-hydroxysteroid dehydrogenase type 1 and the glucocorticoid receptor.

OBJECTIVES: We aimed to investigate whether five potential functional haplotypes of the glucocorticoid receptor (GR) gene and a single-nucleotide polymorphism of 11ß-hydroxysteroid dehydrogenase type 1 (HSD11B1) are associated with clinical outcome in ANCA-associated vasculitis. METHODS: Patients diagnosed with ANCA-associated vasculitis (n = 241) were genotyped for five polymorphisms of the GR gene and one polymorphism of the HSD11B1 gene. GR gene haplotypes were predicted based on genotyping results. Relapse-free survival, mortality, renal survival, metabolic adverse events and infections were compared between carriers and non-carriers of GR haplotypes and the HSD11B1 genotype. RESULTS: Carriers of haplotype 4 (ER22/23EK + 9ß+TthIII1) of GR had a significantly higher 5-year mortality risk [hazard ratio (HR) 4.5 (95% CI 1.6, 12.8)] and had a higher risk of developing end-stage renal disease [HR 7.4 (95% CI 1.9, 28.7)]. Carriers of a minor variant of HSD11B1 more frequently experienced relapse [HR 2.5 (95% CI 1.5, 4.1)] except if they also carried haplotype 1 (BclI) of GR. Homozygous carriers of haplotype 1 had a higher risk of developing dyslipidaemia [HR 4.1 (95% CI 1.8, 9.6)]. The occurrence of infections did not differ between GR haplotypes and HSD11B1 genotypes. CONCLUSION: Haplotypes 1 and 4 of GR and a polymorphism of the HSD11B1 gene were associated with clinically relevant inflammatory and metabolic outcomes in ANCA-associated vasculitis.

Contribution of pathogenic T helper 1 and 17 cells to bursitis and tenosynovitis in polymyalgia rheumatica.

Background: Although polymyalgia rheumatica (PMR) is a very common rheumatic inflammatory disease, current insight into the pathobiology of PMR is limited and largely based on studies in blood. We investigated T helper 1 (TH1) and T helper 17 (TH17) cell responses in blood, synovial fluid and bursa tissue of patients with PMR. Materials and methods: Blood samples were collected from 18 patients with new-onset PMR and 32 healthy controls. Synovial fluid was aspirated from the inflamed shoulder bursae or biceps tendon sheath of 13 patients. Ultrasound-guided biopsies of the subacromial-subdeltoid (SASD) bursa were obtained from 11 patients. T cells were examined by flow cytometry, immunohistochemistry and immunofluorescence staining. Results: Besides an increase of TH17 (CD4+IL-17+IFN-γ-) cells and T cytotoxic 17 (TC17; CD8+IL-17+IFN-γ-) cells, no other major changes were noted in the circulating T cell compartment of patients with PMR. Absolute numbers of CD4+ and CD8+ T cells were similar in blood and synovial fluid of patients with PMR. Synovial fluid T cells showed an effector-memory (CD45RO+CCR7-) phenotype. Percentages of TH1 (CD4+IFN-γ+IL-17-) cells and TH1/TH17 (CD4+IFN-γ+IL-17+) cells, but not TH17 or TC17 cells, were increased in the synovial fluid. Bursa tissue biopsies contained a small number of T cells, which were mostly CD8 negative. The majority of bursa tissue T cells produced IFN-γ but not IL-17. For comparison, B cells were scarcely detected in the bursa tissue. Conclusion: Although the circulating TH17 cell pool is expanded in patients with PMR, our findings indicate that TH1 cells are involved in the inflammation of bursae and tendon sheaths in this condition. Our study points towards the TH1 cell pathway as a potential target for therapy in PMR.

Disturbed Th1, Th2, Th17 and T(reg) balance in patients with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease accompanied by disturbed T-cell homeostasis. Dysbalance of T-helper-cell (Th) subsets (Th1/Th2/Th17) and regulatory T-cells (T(regs)) is suggested to contribute to the pathogenesis of SLE. Recent reports suggest functional deviation of T(regs) in terms of producing IL-17A, a process that may be aberrant in SLE. Therefore, we analyzed these T-cell subsets in SLE to test the hypothesis that aberrant T-cell subset skewing is present in SLE-patients. We investigated simultaneously the intracellular cytokines IFN-γ, IL-4 and IL-17A in CD4(+)T-cells as well as in T(regs). Skewing of T-cell subsets towards Th17 cells was observed in SLE-patients. Although the proportion of T(regs) was similar between SLE-patients and healthy controls, the ability of T(regs) to express IFN-γ and IL17A was impaired in SLE-patients. Even in quiescent SLE-patients T-cell homeostasis is aberrant in terms of skewing towards IL-17 producing T-cells.

Cell-mediated immune responses to influenza vaccination in Wegener's granulomatosis.

BACKGROUND: Both antibody and cell-mediated immune responses are involved in the defence against influenza. In Wegener's granulomatosis (WG), antibody responses to influenza vaccination appear to be similar to those in healthy controls, but cell-mediated responses have not been studied. OBJECTIVE: To determine whether cell-mediated responses to influenza vaccination in WG vary from those in controls. METHODS: Twenty-five patients with WG and healthy controls received subunit influenza vaccine. Peripheral blood mononuclear cells were obtained before and 1 month after vaccination. Cell-mediated responses to A/H1N1 and A/H3N2 were assessed using interferon gamma (IFN gamma) ELISpot and intracellular cytokine staining for IFN gamma, tumour necrosis factor and interleukin 2. RESULTS: Before vaccination, patients and controls showed similar recall responses to A/H1N1 and A/H3N2. After vaccination, patients and controls showed similar levels of increase in spot-forming cells against A/H1N1 and A/H3N2. By flow cytometry, upon vaccination, proportions of cytokine-producing CD4 T cells increased in patients and controls for A/H1N1 and A/H3N2. CONCLUSIONS: Cell-mediated responses to influenza vaccination in patients with WG are comparable to those in healthy controls.

Autoantibodies against glomerular endothelial cells in anti-neutrophil cytoplasmic autoantibody-associated systemic vasculitis.

AIM: The prevalence of anti-endothelial cell autoantibodies (AECA) in patients with anti-neutrophil cytoplasmic autoantibody-associated systemic vasculitis (ASV) has been reported by several groups with conflicting results ranging from 8% to 100%. Types of substrate cells used for AECA testing partially explain this variation. Endothelial cells from kidney origin have been reported to be predominant in AECA binding. Therefore, we investigated AECA prevalence using a human glomerular endothelial cell line compared with primary human umbilical vein endothelial cells, which have frequently been used for AECA detection. METHODS: Sera from 43 ASV patients (29 Wegener's granulomatosis (WG), 14 microscopic polyangiitis (MPA)) with active disease were assessed for AECA positivity using cell-based enzyme-linked immunosorbent assay. Forty serum samples from healthy controls were tested in parallel. To evaluate endothelial activation levels, soluble intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 were measured with capture enzyme-linked immunosorbent assay. RESULTS: The AECA were detected in 4 of 29 WG patients (14%), but none of 14 MPA patients was positive for AECA using glomerular endothelial cell as a substrate, whereas AECA were positive in 10% of WG patients and 14% of MPA patients on human umbilical vein endothelial cells. No significant differences were found between ASV patients and controls in AECA test. Serum levels of vascular cell adhesion molecule-1 and soluble intercellular cell adhesion molecule-1 in ASV patients were significantly higher than in controls. However, there were no differences between AECA-positive and -negative patients for both of the activation markers. CONCLUSION: The AECA, directed against glomerular endothelial cells, have a low prevalence in ASV patients with active disease and are not correlated with endothelial activation.

Decreased Expression of Negative Immune Checkpoint VISTA by CD4+ T Cells Facilitates T Helper 1, T Helper 17, and T Follicular Helper Lineage Differentiation in GCA.

Loss of immune checkpoint (IC) Programmed Death-1 (PD-1) and PD-Ligand1 (PD-L1) expression has been implicated in the immunopathology of Giant Cell Arteritis (GCA). The contribution of the negative immune checkpoint V-domain Immunoglobulin-containing suppressor of T cell activation (VISTA) to GCA pathology has not yet been studied. The aim of our study was to investigate if expression of VISTA and other IC molecules by peripheral blood (PB) immune cells is modulated in GCA and at the site of vascular inflammation. In addition, we assessed the effect of VISTA-Ig engagement on in vitro CD4+ T helper (Th) lineage differentiation. To this end, frequencies of monocytes expressing CD80/86, PD-L1, PD-L2, and VISTA were determined in blood samples from 30 GCA patients and 18 matched healthy controls by flow cytometry. In parallel, frequencies of CD4+ cells expressing CD28, Cytotoxic T-Lymphocyte-associated antigen-4 (CTLA-4), PD-1, and VISTA were determined. Immunohistochemistry was employed to detect VISTA, PD-1, and PD-L1-expressing cells in temporal artery biopsies (TABs) diagnostic of GCA. Furthermore, the effect of VISTA-Ig on in vitro CD4+ Th lineage differentiation in patients and controls was determined. Our study shows that frequencies of CD80/CD86+ and VISTA+ monocytes were decreased in treated GCA patients only. Moreover, proportions of PD-1+ and VISTA+ Th cells were significantly decreased in GCA patients. Clear infiltration of VISTA+, PD1+, and PD-L1+ cells was seen in GCA TABs. Finally, VISTA-Ig engagement failed to suppress Th1, Th17, and Tfh lineage development in GCA. Our results indicate that decreased expression of VISTA may facilitate development of pathogenic Th1 and Th17 cells in GCA.

Rats and mice immunised with chimeric human/mouse proteinase 3 produce autoantibodies to mouse Pr3 and rat granulocytes.

AIM: In this study, we employed chimeric human/mouse Proteinase 3 (PR3) proteins as tools to induce an autoantibody response to PR3 in rats and mice. METHOD: Rats and mice were immunised with recombinant human PR3 (HPR3), recombinant murine PR3 (mPR3), single chimeric human/mouse PR3 (HHm, HmH, mHH, mmH, mHm, Hmm) or pools of chimeric proteins. Antibodies to mPR3 and HPR3 were measured by ELISA. Antibodies to rat PR3 were determined by indirect immunofluorescence (IIF) on rat white blood cells. Urinalysis was performed by dipstick analysis. Kidney and lung tissue was obtained for pathological examination. RESULTS: In mice, immunisation with the chimeric human/mouse PR3 Hmm led to an autoantibody response to mPR3. Rats immunised with the chimeric human/mouse PR3 Hmm, HmH and mmH, or a pool of the chimeric human/mouse PR3 proteins, produced antibodies selectively binding to rat granulocytes as detected by IIF. No gross pathological abnormalities could be detected in kidney or lungs of mice or rats immunised with chimeric human/mouse PR3. CONCLUSION: Immunisation with chimeric human/mouse proteins induces autoantibodies to PR3 in rats and mice. Chimeric proteins can be instrumental in developing experimental models for autoimmune diseases.

B Cell Depletion Therapy Normalizes Circulating Follicular Th Cells in Primary Sjögren Syndrome.

OBJECTIVE: To assess the effect of B cell depletion therapy on effector CD4+ T cell homeostasis and its relation to objective measures of disease activity in patients with primary Sjögren syndrome (pSS). METHODS: Twenty-four patients with pSS treated with rituximab (RTX) and 24 healthy controls (HC) were included. Frequencies of circulating effector CD4+ T cell subsets were examined by flow cytometry at baseline and 16, 24, 36, and 48 weeks after the first RTX infusion. Th1, Th2, follicular Th (TFH), and Th17 cells were discerned based on surface marker expression patterns. Additionally, intracellular cytokine staining was performed for interferon-γ, interleukin (IL)-4, IL-21, and IL-17 and serum levels of these cytokines were analyzed. RESULTS: In patients with pSS, frequencies of circulating TFH cells and Th17 cells were increased at baseline compared with HC, whereas frequencies of Th1 and Th2 cells were unchanged. B cell depletion therapy resulted in a pronounced decrease in circulating TFH cells, whereas Th17 cells were only slightly lowered. Frequencies of IL-21-producing and IL-17-producing CD4+ T cells and serum levels of IL-21 and IL-17 were also reduced. Importantly, the decrease in circulating TFH cells was associated with lower systemic disease activity over time, as measured by the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index scores and serum IgG levels. CONCLUSION: B cell depletion therapy in patients with pSS results in normalization of the elevated levels of circulating TFH cells. This reduction is associated with improved objective clinical disease activity measures. Our observations illustrate the pivotal role of the crosstalk between B cells and TFH cells in the pathogenesis of pSS.

Constitutive membrane expression of proteinase 3 (PR3) and neutrophil activation by anti-PR3 antibodies.

Antineutrophil cytoplasm autoantibodies with specificity for proteinase 3 (PR3) are thought to play a major role in the pathogenesis of Wegener's granulomatosis (WG), presumably by their potential to activate neutrophils. In patients with WG, high expression of PR3 on the surface of nonprimed neutrophils is associated with an increased incidence and rate of relapse. In this study, we analyzed the functional significance of constitutive PR3 expression for neutrophil activation as induced by anti-PR3 antibody. Therefore, primed and nonprimed neutrophils were stimulated with the monoclonal anti-PR3 antibody PR3G-3. Activation was measured as actin polymerization by the phalloidin assay as an early, detectable activation event and oxidative burst by the dihydrorhodamine assay, as a late, detectable activation event. In contrast to the oxidative burst, we found that anti-PR3 antibody-induced actin polymerization could be triggered in neutrophils without priming with tumor necrosis factor alpha (TNF-alpha). In addition, a correlation was found between the level of PR3 expression on the surface of these nonprimed neutrophils and the degree of actin polymerization. However, after priming with TNF-alpha, no correlation was found between membrane expression of PR3 and the level of actin polymerization or respiratory burst as induced by anti-PR3 antibody. These data suggest that the presence of PR3 on the surface of nonprimed neutrophils has consequences for their susceptibility to the initial activation step by anti-PR3 antibodies. These data may be relevant in view of the observed relation between membrane expression of PR3 on nonprimed neutrophils of patients with WG and their susceptibility for relapses.

Expression of Lectin-Like Transcript 1, the Ligand for CD161, in Rheumatoid Arthritis.

OBJECTIVES: Precursor Th17 lineage cells expressing CD161 are implicated in Rheumatoid Arthritis (RA) pathogenesis. CD4+CD161+ T-cells accumulate in RA joints and may acquire a non classical Th1 phenotype. The endogenous ligand for CD161 is lectin-like transcript 1 (LLT1). CD161/LLT1 ligation may co-stimulate T-cell IFN-γ production. We investigated the presence and identity of LLT1-expressing cells in RA synovial fluid (SF) and synovial tissue (ST). We also assessed levels of soluble LLT1 (sLLT1) in different phases of RA development. METHODS: Paired samples of peripheral blood mononuclear cells (MC) and SFMC (n = 14), digested ST cells (n = 4) and ST paraffin sections (n = 6) from late-stage RA were analyzed for LLT1 expression by flow cytometry and immunohistochemistry. sLLT1 was measured using a sandwich ELISA. Sera and SF from late-stage RA (n = 26), recently diagnosed RA patients (n = 39), seropositive arthralgia patients (SAP, n = 31), spondyloarthropathy patients (SpA, n = 26) and healthy controls (HC, n = 31) were assayed. RESULTS: In RA SF, LLT1 was expressed by a small proportion of monocytes. In RA ST, LLT1-expressing cells were detected in the lining, sublining layer and in areas with infiltrates. The LLT1 staining pattern overlapped with the CD68 staining pattern. FACS analysis of digested ST confirmed LLT1 expression by CD68+ cells. Elevated systemic sLLT1 was found in all patient groups. CONCLUSIONS: In RA joints, LLT1 is expressed by cells of the monocyte/macrophage lineage. Serum levels of sLLT1 were increased in all patient groups (patients with early- and late-stage RA, seropositive arthralgia and spondyloarthropathy) when compared to healthy subjects.

Intermediate monocytes in ANCA vasculitis: increased surface expression of ANCA autoantigens and IL-1ß secretion in response to anti-MPO antibodies.

ANCA vasculitis encompasses several autoimmune conditions characterised by destruction of small vessels, inflammation of the respiratory tract and glomerulonephritis. Most patients harbour autoantibodies to myeloperoxidase (MPO) or proteinase 3 (PR3). Clinical and experimental data suggest that pathogenesis is driven by ANCA-mediated activation of neutrophils and monocytes. We investigated a potential role for distinct monocyte subsets. We found that the relative proportion of intermediate monocytes is increased in patients versus control individuals, and both MPO and PR3 are preferentially expressed on these cells. We demonstrate that MPO and PR3 are expressed independently of each other on monocytes and that PR3 is not associated with CD177. MPO expression correlates with that of Fc receptor CD16 on intermediate monocytes. Monocyte subsets respond differently to antibodies directed against MPO and PR3, with anti-MPO but not anti-PR3 leading to increased IL-1ß, IL-6 and IL-8 production. In concordance with the observed higher surface expression of MPO on intermediate monocytes, this subset produces the highest quantity of IL-1ß in response to anti-MPO stimulation. These data suggest that monocytes, specifically, the intermediate subset, may play a role in ANCA vasculitis, and also indicate that substantial differences exist between the effect of anti-MPO and anti-PR3 antibodies on these cells.

Recombinant protein to analyze autoantibodies to proteinase 3 in systemic vasculitis.

The presence of antineutrophil cytoplasmic autoantibodies with specificity for proteinase 3 (PR3-ANCA) usually is detected by enzyme-linked immunosorbent assay (ELISA) with purified PR3 as a substrate. We studied the technical performance of direct and capture ELISA using a recombinant proteolytically inactive form of PR3 produced in the baculovirus expression system for the detection of PR3-ANCA in 114 patients with systemic vasculitis at diagnosis. We found that ELISA using recombinant PR3 produced in insect cells is a promising alternative for ELISA with native PR3. We found a correlation between tests using recombinant or native PR3, as well as correlation of the ELISA results with ANCA titers measured by the indirect immunofluorescence technique. However, the specificity for ANCA-associated vasculitis of ELISA with recombinant PR3 was lower than ELISA using native PR3. Compared with the direct assay, capture ELISA is a more sensitive method for PR3-ANCA detection, with both native and recombinant PR3, and its results depend on the monoclonal antibody used to capture the antigen.

Differential expression of granulopoiesis related genes in neutrophil subsets distinguished by membrane expression of CD177.

OBJECTIVE: Differential gene expression in CD177+ and CD177- neutrophils was investigated, in order to detect possible differences in neutrophil function which could be related to the pathogenesis of ANCA-associated Vasculitides (AAV). METHODS: Neutrophils were isolated from healthy controls (HC) with high, negative or bimodal CD177 expression, and sorted into CD177+ and CD177- subpopulations. Total RNA was screened for expression of 24,000 probes with Illumina Ref-8 Beadchips. Genes showing differential expression between CD177+ and CD177- subsets in microarray analysis were re-assessed using quantitative-PCR. CD177 expression on neutrophil precursors in bone marrow was analyzed using quantitative PCR and flowcytometry. RESULTS: The proportion of CD177+ cells increased during neutrophil maturation in bone marrow. Fold change analysis of gene expression profile of sorted CD177+ and CD177- neutrophils resulted in 14 genes with fold change (fc) >3 difference in expression. Interestingly, 10 of these genes have been reported to change significantly in expression during neutrophil maturation, and most of these genes were granule protein (GP) coding genes. mRNA expression levels measured by RT-PCR of a number of these GP, and of PR3 and MPO were higher in the CD177- neutrophil subset in HC, however, particular granule protein amounts were comparable between CD177+ and CD177- neutrophil subsets. AAV patients had higher amounts of CD177+ neutrophils, but contrary to neutrophils from HC expression of GP-genes was increased, possibly due to activation. CONCLUSION: The neutrophil population can be distinguished by membrane expression of CD177 into subsets that are different in expression of GP mRNA but not in GP protein production. GP gene expression is also elevated in AAV patients, which is not explained by skewed distribution of CD177+ and CD177- subsets but may be associated with neutrophil activation during on-going inflammation.

Disturbed B cell homeostasis in newly diagnosed giant cell arteritis and polymyalgia rheumatica.

OBJECTIVE: Several lines of evidence indicate that B cells may be involved in the immunopathology of giant cell arteritis (GCA) and polymyalgia rheumatica (PMR). This study was undertaken to examine the distribution of defined B cell subsets, including effector B (Beff) cells and regulatory B (Breg) cells, in patients with GCA and patients with PMR before and after corticosteroid treatment. METHODS: Circulating B cells were analyzed in 34 newly diagnosed, untreated patients with GCA or PMR, and in 44 followup samples from patients with GCA or PMR who received corticosteroids for 2 weeks or 3 months. For comparison, 40 age-matched healthy controls and 11 rheumatoid arthritis (RA) patients were included. Serum BAFF levels were determined, and temporal arteries were studied by immunohistochemistry. RESULTS: Patients newly diagnosed as having GCA or PMR, but not patients with RA, had decreased numbers of circulating B cells compared to healthy controls. B cell numbers recovered rapidly in treated patients with GCA and PMR in remission. This recovery was not achieved by compensatory hyperproliferation or enhanced bone marrow production. B cell numbers inversely correlated with erythrocyte sedimentation rates, C-reactive protein levels, and serum BAFF levels. Tumor necrosis factor α-positive Beff cells, but not interleukin-10 (IL-10)-positive Breg cells, were decreased in patients newly diagnosed as having GCA or PMR. Following treatment, circulating numbers of Beff cells normalized. The returning Beff cells demonstrated an enhanced capacity to produce IL-6. Few B cells were found in temporal artery biopsy specimens from GCA patients. CONCLUSION: We show for the first time that the distribution of B cells is highly disturbed in GCA and PMR and that B cells likely contribute to the enhanced IL-6 response in both diseases.

Circulating CD4+CD161+ T lymphocytes are increased in seropositive arthralgia patients but decreased in patients with newly diagnosed rheumatoid arthritis.

Improved understanding of the immune events discriminating between seropositive arthralgia and clinical synovitis is of key importance in rheumatology research. Ample evidence suggests a role for Th17 cells in rheumatoid arthritis. We hypothesized that CD4+CD161+ cells representing Th17 lineage cells may be modulated prior to or after development of clinical synovitis. Therefore, in a cross-sectional study, we investigated the occurrence of CD4+CD161+ T-cells in seropositive arthralgia patients who are at risk for developing rheumatoid arthritis and in newly diagnosed rheumatoid arthritis patients. In a prospective study, we evaluated the effect of methotrexate treatment on circulating CD4+CD161+ T-cells. Next, we assessed if these cells can be detected at the level of the RA joints. Precursor Th17 lineage cells bearing CD161 were found to be increased in seropositive arthralgia patients. In contrast, circulating CD4+CD161+T-cells were decreased in newly diagnosed rheumatoid arthritis patients. The decrease in CD4+CD161+ T-cells correlated inversely with C-reactive protein and with the 66 swollen joint count. Methotrexate treatment led to normalization of CD4+CD161+ T-cells and reduced disease activity. CD4+CD161+ T cells were readily detected in synovial tissues from both early and late-stage rheumatoid arthritis. In addition, synovial fluid from late-stage disease was found to be enriched for CD4+CD161+ T-cells. Notably, synovial fluid accumulated CD4+CD161+T-cells showed skewing towards the Th1 phenotype as evidenced by increased interferon-γ expression. The changes in peripheral numbers of CD4+CD161+ T-cells in seropositive arthralgia and early rheumatoid arthritis and the enrichment of these cells at the level of the joint predict a role for CD4+CD161+ T-cells in the early immune events leading to clinical synovitis. Our findings may add to the development of RA prediction models and provide opportunities for early intervention.

Increased frequency of circulating IL-21 producing Th-cells in patients with granulomatosis with polyangiitis (GPA).

INTRODUCTION: The present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA). METHODS: Peripheral blood from 42 GPA patients in remission and 29 age-matched healthy controls (HCs) were stimulated in vitro, and the frequencies of IL-21 producing Th-cells were determined by flow cytometry. Since Th17-cells produce a low level of IL-21, IL-17 was also included in the analysis. Given that IL-21 is a hallmark cytokine for T follicular helper cells (T(FH)), we next evaluated the expression of their key transcription factor BCL-6 by RT-PCR and flow cytometry. To investigate the effect of IL-21 on autoantibody-production, PBMCs from GPA patients were stimulated in vitro with BAFF/IL-21 and total IgG and ANCA levels were measured in supernatants. In addition, the expression of IL-21-receptor on B-cells was analyzed. RESULTS: Percentages of IL-21 producing Th-cells were significantly elevated in GPA-patients compared to HCs, and were restricted to ANCA-positive patients. The expression of BCL-6 was significantly higher in ANCA-positive GPA-patients, as compared with ANCA-negative patients and HCs. IL-21 enhanced the production of IgG and ANCA in vitro in stimulated PBMCs from GPA patients. No difference was found in the expression of the IL-21-receptor on B-cells between ANCA-negative patients, ANCA-positive patients, and HCs. CONCLUSION: The increased frequency of circulating IL-21 producing Th-cells in ANCA-positive GPA patients and the stimulating capacity of IL-21 on ANCA-production suggest a role for these cells in the immunopathogenesis of GPA. Blockade of IL-21 could constitute a new therapeutic strategy for GPA.

CCR5Δ32 genotype leads to a Th2 type directed immune response in ESRD patients.

BACKGROUND: In patients with end stage renal disease (ESRD) we observed protection from inflammation-associated mortality in CCR5Δ32 carriers, leading to CCR5 deficiency, suggesting impact of CCR5Δ32 on inflammatory processes. Animal studies have shown that CCR5 deficiency is associated with a more pronounced Th2 type immune response, suggesting that in human CCR5Δ32 carriers the immune response may be more Th2 type directed. So, in the present study we determined the Th1-Th2 type directed immune response in ESRD patients carrying and not carrying the CCR5Δ32 genetic variant after stimulation. METHODOLOGY/PRINCIPAL FINDINGS: We tested this hypothesis by determining the levels of IFN-γ and IL-4 and the distribution of Th1, Th2 and Th17 directed circulating CD4+ and CD8+ T cells and regulatory T cells (Tregs) after stimulation in ESRD patients with (n = 10) and without (n = 9) the CCR5Δ32 genotype. The extracellular levels of IFN-γ and IL-4 did not differ between CCR5Δ32 carriers and non carriers. However, based on their intracellular cytokine profile the percentages IL-4 secreting CD4+ and CD8+ T cells carrying the CCR5Δ32 genotype were significantly increased (p = 0.02, respectively p = 0.02) compared to non carriers, indicating a more Th2 type directed response. Based on their intracellular cytokine profile the percentages IFN-γ and IL-17 secreting T cells did not differ between carriers and non-carriers nor did the percentage Tregs, indicating that the Th1, Th17 and T regulatory response was not affected by the CCR5Δ32 genotype. CONCLUSIONS/SIGNIFICANCE: This first, functional human study shows a more pronounced Th2 type immune response in CCR5Δ32 carriers compared to non carriers. These differences may be involved in the previously observed protection from inflammation-associated mortality in ESRD patients carrying CCR5Δ32.