Increased expression of CTLA-4 (CD152) by T and B lymphocytes in Wegener's granulomatosis

ANCA-associated vasculitis and lung cancer: an immunological perspective

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a severe autoimmune disease that often involves the upper and lower respiratory tracts. In recent years, numerous studies have found a significant increase in the incidence of cancer among AAV patients, but the association between lung cancer and AAV remains inconclusive, with relatively low clinical attention. This review summarizes the current literature on the risk of lung cancer in patients with ANCA-associated vasculitis (AAV), detailing the potential mechanisms by which AAV may contribute to lung cancer, and further elucidates the inherent carcinogenic risks of immunosuppressants.There is a correlation between AAV and lung cancer, which is related to T cell senescence and damage, as well as the abnormal expression of cytokines such as IL-6 and IL-10. In AAV patients, the use of cyclophosphamide and azathioprine (AZA) alone has a clear carcinogenic risk, with frequent use of CYC potentially posing a high risk for lung cancer. Although TNF inhibitors (TNFi) combined with CYC have carcinogenic risks, there is insufficient evidence to link them directly to an increased risk of lung cancer. For patients at high risk for lung cancer, the judicious use of immunosuppressants, timely computed tomography (CT), and lung cancer screening can reduce the risk of lung cancer in AAV patients.

Catecholamines' accumulation and their disturbed metabolism at perilesional site: a possible cause of vitiligo progression

Catecholamines (epinephrine, norepinephrine and dopamine) are considered toxic to the melanocytes and may play an important role in the development of depigmented patches on the skin. This study was done to evaluate the levels of catecholamines in skin and plasma samples of active vitiligo patients' and gene expression changes in catecholamines' metabolism regulatory genes (COMT and GTPCH1), immunoregulatory genes (CTLA4 and PTPN22), and Catalase in active vitiligo patients. In this single-centre, prospective, case-control study, 30 patients with active vitiligo were recruited and skin biopsies from the perilesional site and plasma samples were collected. Skin biopsies from the normal site in vitiligo patients and healthy controls (n = 15) and plasma samples from controls were also obtained. Catecholamines' estimation was done via high-performance liquid chromatography. Gene expression variations were investigated via reverse transcription-polymerase chain reaction (PCR) and real-time PCR. Epinephrine, norepinephrine and dopamine levels were significantly higher in perilesional skin biopsies as compared to controls (P = 0.035, 0.024, and 0.006, respectively). However, epinephrine, norepinephrine and dopamine levels observed in patients' plasma samples were comparable to controls. The mRNA expression level of the Catalase gene was found to be upregulated at the perilesional site of patients as compared to the non-affected site of same patients (P < 0.001) and healthy controls (P = 0.037). Transcriptional expression of GTPCH1 and COMT were observed to be increased significantly at the perilesional site of patients in comparison to controls (P = 0.004 and P = 0.046, respectively). Our results support the presence of oxidative stress, inflammation and induced immune response in vitiligo patients at the perilesional sites. The increased inflammatory response may lead to catecholamines upregulation resulting in oxidative stress and melanocyte damage.

Targeting immune checkpoints in anti-neutrophil cytoplasmic antibodies associated vasculitis: the potential therapeutic targets in the future

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) is a necrotizing vasculitis mainly involving small blood vessels. It is demonstrated that T cells are important in the pathogenesis of AAV, including regulatory T cells (Treg) and helper T cells (Th), especially Th2, Th17, and follicular Th cells (Tfh). In addition, the exhaustion of T cells predicted the favorable prognosis of AAV. The immune checkpoints (ICs) consist of a group of co-stimulatory and co-inhibitory molecules expressed on the surface of T cells, which maintains a balance between the activation and exhaustion of T cells. CD28, inducible T-cell co-stimulator (ICOS), OX40, CD40L, glucocorticoid induced tumor necrosis factor receptor (GITR), and CD137 are the common co-stimulatory molecules, while the programmed cell death 1 (PD-1), cytotoxic T lymphocyte-associated molecule 4 (CTLA-4), T cell immunoglobulin (Ig) and mucin domain-containing protein 3 (TIM-3), B and T lymphocyte attenuator (BTLA), V-domain Ig suppressor of T cell activation (VISTA), T-cell Ig and ITIM domain (TIGIT), CD200, and lymphocyte activation gene 3 (LAG-3) belong to co-inhibitory molecules. If this balance was disrupted and the activation of T cells was increased, autoimmune diseases (AIDs) might be induced. Even in the treatment of malignant tumors, activation of T cells by immune checkpoint inhibitors (ICIs) may result in AIDs known as rheumatic immune-related adverse events (Rh-irAEs), suggesting the importance of ICs in AIDs. In this review, we summarized the features of AAV induced by immunotherapy using ICIs in patients with malignant tumors, and then reviewed the biological characteristics of different ICs. Our aim was to explore potential targets in ICs for future treatment of AAV.

Unraveling the Immunopathogenesis and Genetic Variants in Vasculitis Toward Development of Personalized Medicine

Leukocytoclastic vasculitis (LCV) is a systemic autoimmune disease characterized by the inflammation of the vascular endothelium. Cutaneous small vessel vasculitis (CSVV) and anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) are two examples of LCV. Advancements in genomic technologies have identified risk haplotypes, genetic variants, susceptibility loci and pathways that are associated with vasculitis immunopathogenesis. The discovery of these genetic factors and their corresponding cellular signaling aberrations have enabled the development and use of novel therapeutic strategies for vasculitis. Personalized medicine aims to provide targeted therapies to individuals who show poor response to conventional interventions. For example, monoclonal antibody therapies have shown remarkable efficacy in achieving disease remission. Here, we discuss pathways involved in disease pathogenesis and the underlying genetic associations in different populations worldwide. Understanding the immunopathogenic pathways in vasculitis and identifying associated genetic variations will facilitate the development of novel and targeted personalized therapies for patients.

Categorisation of patients based on immune profiles: a new approach to identifying candidates for response to checkpoint inhibitors

Objectives

Inhibitors to the checkpoint proteins cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) are becoming widely used in cancer treatment. However, a lack of understanding of the patient response to treatment limits accurate identification of potential responders to immunotherapy.

Methods

In this study, we assessed the expression of PD-1 and CTLA-4 on 19 leucocyte populations in the peripheral blood of 74 cancer patients. A reference data set for PD-1 and CTLA-4 was established for 40 healthy volunteers to determine the normal expression patterns for these checkpoint proteins.

Results

Unsupervised hierarchical clustering found four immune profiles shared across the solid tumor types, while chronic lymphocytic leukaemia patients had an immune profile largely unique to them. Furthermore, we measured these leucocyte populations on an additional cohort of 16 cancer patients receiving the PD-1 inhibitor pembrolizumab in order to identify differences between responders and non-responders, as well as compared to healthy volunteers (n = 20). We observed that cancer patients had pre-treatment PD-1 and CTLA-4 expression on their leucocyte populations at different levels compared to healthy volunteers and identified two leucocyte populations positive for CTLA-4 that had not been previously described. We found higher levels of PD-1⁺ CD3⁺ CD4^- CD8^- cells in patients with progressive disease and have identified it as a potential biomarker of response, as well as identifying other significant differences in phenotypes between responders and non-responders.

Conclusion

These results are suggestive that categorisation of patients based on immune profiles may differentiate responders from non-responders to immunotherapy for solid tumors.

Immune Checkpoints, a Novel Class of Therapeutic Targets for Autoimmune Diseases

Autoimmune diseases, such as multiple sclerosis and type-1 diabetes, are the outcomes of a failure of immune tolerance. Immune tolerance is sustained through interplays between two inter-dependent clusters of immune activities: immune stimulation and immune regulation. The mechanisms of immune regulation are exploited as therapeutic targets for the treatment of autoimmune diseases. One of these mechanisms is immune checkpoints (ICPs). The roles of ICPs in maintaining immune tolerance and hence suppressing autoimmunity were revealed in animal models and validated by the clinical successes of ICP-targeted therapeutics for autoimmune diseases. Recently, these roles were highlighted by the clinical discovery that the blockade of ICPs causes autoimmune disorders. Given the crucial roles of ICPs in immune tolerance, it is plausible to leverage ICPs as a group of therapeutic targets to restore immune tolerance and treat autoimmune diseases. In this review, we first summarize working mechanisms of ICPs, particularly those that have been utilized for therapeutic development. Then, we recount the agents and approaches that were developed to target ICPs and treat autoimmune disorders. These agents take forms of fusion proteins, antibodies, nucleic acids, and cells. We also review and discuss safety information for these therapeutics. We wrap up this review by providing prospects for the development of ICP-targeting therapeutics. In summary, the ever-increasing studies and results of ICP-targeting of therapeutics underscore their tremendous potential to become a powerful class of medicine for autoimmune diseases.

New Insights Into Novel Therapeutic Targets in ANCA-Associated Vasculitis

Biologics targeting inflammation-related molecules in the immune system have been developed to treat rheumatoid arthritis (RA), and these RA treatments have provided revolutionary advances. Biologics may also be an effective treatment for anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis, particularly in patients with resistance to standard treatments. Despite the accumulation of clinical experience and the increasing understanding of the pathogenesis of vasculitis, it is becoming more difficult to cure vasculitis. The treatment of vasculitis with biologics has been examined in clinical trials, and this has also enhanced our understanding of the pathogenesis of vasculitis. A humanized anti-interleukin-5 monoclonal antibody known as mepolizumab was recently demonstrated to provide clinical benefit in the management of eosinophilic granulomatosis with polyangiitis in refractory and relapsing disease, and additional new drugs for vasculitis are being tested in clinical trials, while others are in abeyance. This review presents the new findings regarding biologics in addition to the conventional immunosuppressive therapy for ANCA-associated vasculitis.

Antineutrophil Cytoplasmic Antibody-Associated Vasculitis Update: Genetic Pathogenesis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by the inflammation of small and medium vessels and presence of proteinase 3-ANCA or myeloperoxidase-ANCA in the circulation. AAV comprises three clinical subtypes: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (EGPA). Although the pathogenesis of AAV is still unclear, genetic and environmental factors and the immune system are thought to be involved. Genetic factors have been confirmed to play an important role in AAV. Genome-wide association studies have identified numerous genetic variants in MHC and non-MHC regions associated with AAV. The strongest evidence of MHC association in AAV is human leukocyte antigen (HLA)-DP. A significant association between AAV and genetic variations in non-MHC regions, such as CTLA-4, FCGR2A, PTPN22, SERPINA1, and TLR9 has also been found. Moreover, different clinical subtypes of AAV have distinct genetic backgrounds. GPA is associated with HLA-DP1, MPA with HLA-DQ, and EGPA with HLA-DRB4. These findings could help elucidate the etiology of AAV and develop new biomarkers for diagnosis and targeted therapy. Herein, we briefly summarize the updates on the genetic pathogenesis and biomarkers of AAV.

The Co-inhibitor BTLA Is Functional in ANCA-Associated Vasculitis and Suppresses Th17 Cells

Objectives: The activation and inhibition of T-cells has been well-studied under physiological conditions. Co-inhibition is an important mechanism to keep effector T-cells in check. Co-inhibitors mediate peripheral self-tolerance and limit the immune response. Dysfunctional co-inhibition is associated with loss of T-cell regulation and induction of autoimmunity. Therefore, we investigated the co-inhibitor B- and T-Lymphocyte attenuator (BTLA) in ANCA-associated vasculitis (AAV). Methods: Fifty-six AAV patients and 32 healthy controls (HC) were recruited. Flow cytometry was performed to investigate the expression of BTLA on T-cells. Double negative T-cells were defined as CD3⁺CD4^-CD8^-. To assess the functionality of BTLA, CFSE-labeled T-cells were stimulated in presence or absence of an agonistic anti-BTLA antibody. In addition, impact of BTLA-mediated co-inhibition on Th17 cells was studied. Results: AAV patients in remission had a decreased expression of BTLA on double negative T-cells (CD3⁺CD4^-CD8^-). On all other subtypes of T-cells, expression of BTLA was comparable to healthy controls. TCR-independent stimulation of T-cells resulted in down-regulation of BTLA on Th cells in AAV and HC, being significantly lower in HC. Co-inhibition via BTLA led to suppression of T-cell proliferation in AAV as well as in HC. As a result of BTLA mediated co-inhibition, Th17 cells were suppressed to the same extent in AAV and HC. Conclusion: BTLA expression is altered on double negative T-cells but not on other T-cell subsets in quiescent AAV. BTLA-induced co-inhibition has the capacity to suppress Th17 cells and is functional in AAV. Thus, BTLA-mediated co-inhibition might be exploited for future targeted therapies in AAV.

T-lymphocyte in ANCA-associated vasculitis: what do we know? A pathophysiological and therapeutic approach

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune condition that commonly causes kidney impairment and can be fatal. The key participation of B-lymphocytes as ANCA producers and neutrophils as target of these antibodies is widely described as the mechanism of endothelial damage in this disease. There has been a rising interest in the role of T-lymphocytes in AAV in recent years. Evidence is strong from animal models, and T-lymphocytes can be found infiltrating kidney tissue and other tissue sites in AAV patients. Furthermore, the different subsets of T-lymphocytes are also key players in the aberrant immune response observed in AAV. Polarization towards a predominant Th1 and Th17 response in the acute phase of the disease has been described, along with a decline in the number of T-regulatory lymphocytes, which, in turn, show functional impairment. Interactions between different T-cell subsets, and between T-cells and neutrophils and B-cells, also enhance the inflammatory response, constituting a complex network. Novel therapies targeting T-cell immunity are emerging in this scenario and may constitute an interesting alternative to conventional therapy in selected patients. This review aims to summarize the available evidence regarding T-cell imbalances and functional impairment, especially focusing on renal involvement of AAV.

Dysregulation of peritoneal cavity B1a cells and murine primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease with progressive cholestasis and liver fibrosis. Similar to human patients with PBC, p40^−/−IL-2Rα^−/− mice spontaneously develop severe autoimmune cholangitis. Although there has been considerable work on immune regulation and autoimmunity, there is a relative paucity of work directed at the functional implications of the key peritoneal cavity (PC) B cell subset, coined B1a cells in PBC. We used flow cytometry and high-resolution microarrays to study the qualitative and quantitative characteristics of B cells, particularly B1a cells, in the PC of p40^−/−IL-2Rα^−/− mice compared to controls. Importantly, B1a cell proliferation was markedly lower as the expression of Ki67 decreased. Meanwhile, the apoptosis level was much higher. These lead to a reduction of B1a cells in the PC of p40^−/−IL-2Rα^−/− mice compared to controls. In contrast, there was a dramatic increase of CD4⁺ and CD8⁺ T cells accompanied by elevated production of IFN-γ. In addition, we found a negative correlation between the frequency of B1a cells and the presence of autoreactive CD8⁺ T cells in both liver and PC of p40^−/−IL-2Rα^−/− mice. From a functional perspective, B cells from p40^−/−IL-2Rα^−/− mice downregulated IL-10 production and CTLA-4 expression, leading to loss of B cell regulatory function. We suggest that the dysfunction of B1a cells in the PC in this murine model of autoimmune cholangitis results in defective regulatory function. This highlights a new potential therapeutic target in PBC.

CTLA-4 in mesothelioma patients: tissue expression, body fluid levels and possible relevance as a prognostic factor

CTLA-4 function as a negative regulator of T cell-mediated immune response is well established, whereas much less is known about the immunoregulatory role of its soluble isoform (sCTLA-4). No data are available on CTLA-4 expression and prognostic impact in malignant pleural mesothelioma (MPM). We investigated, by immunohistochemistry, CTLA-4 expression in tumor tissues and, by ELISA, sCTLA-4 levels in sera and matched pleural effusions from 45 MPM patients. Prognostic effect of CTLA-4 expression on overall survival (OS) was assessed through Cox regression and prognostic significance expressed as death rate ratio (HR). We found that 56.0 % of MPM tissues expressed CTLA-4 with variable intensity and percentage of positive cells estimated by the immunoreactive score. sCTLA-4 levels were significantly higher in sera (S-sCTLA-4) than in pleural effusions (PE-sCTLA-4) (geometric mean ratio = 2.70, P value = 0.020). CTLA-4 expression at the tissue level was higher in the epithelioid histological subtype than in the sarcomatoid, whereas at the serum level, it was higher in the sarcomatoid subtype. A homogeneous favorable prognostic effect was found for CTLA-4 overexpression in tissue, serum and pleural effusion. Interestingly, only the PE-sCTLA-4 was found to be a statistically significant positive prognostic factor (HR = 0.37, 95 % CI = 0.18-0.77, P value = 0.007). Indeed, PE-sCTLA-4 correlated with CTLA-4 expression in tissues, whereas this latter expression showed a weak association with OS. To confirm our findings, further experimental evidences obtained from a larger cohort of MPM patients are required. However, our results would indicate a positive correlation of PE-sCTLA-4 levels and OS in MPM patients.

An open-label trial of abatacept (CTLA4-IG) in non-severe relapsing granulomatosis with polyangiitis (Wegener's)

OBJECTIVES

To determine the safety and efficacy of abatacept in non-severe relapsing granulomatosis with polyangiitis (Wegener's)(GPA).

METHODS

An open-label trial of intravenous abatacept was conducted in 20 patients with non-severe relapsing GPA. Prednisone up to 30 mg daily was permitted within the first 2 months, and patients on methotrexate, azathioprine, or mycophenolate mofetil continued these agents. Patients remained on study until common closing or early termination.

RESULTS

Of the 20 patients, 18 (90%) had disease improvement, 16 (80%) achieved remission (BVAS/WG=0) at a median of 1.9 months, and 14 (70%) reached common closing. Six patients (30%) met criteria for early termination due to increased disease activity; 3 of 6 achieved remission and relapsed at a median of 8.6 months. The median duration of remission before common closing was 14.4 months, with the median duration of time on study for all patients being 12.3 months (range 2-35 months). Eleven of the 15 (73%) patients on prednisone reached 0 mg. Nine severe adverse events occurred in 7 patients, including 7 infections that were successfully treated.

CONCLUSIONS

In this study of patients with non-severe relapsing GPA, abatacept was well tolerated and was associated with a high frequency of disease remission and prednisone discontinuation.

The engagement of CTLA-4 on primary melanoma cell lines induces antibody-dependent cellular cytotoxicity and TNF-α production

Background

CTLA-4 (Cytotoxic T lymphocyte antigen-4) is traditionally known as a negative regulator of T cell activation. The blocking of CTLA-4 using human monoclonal antibodies, such as Ipilimumab, is currently used to relieve CTLA-4-mediated inhibition of anti-tumor immune response in metastatic melanoma. Herein, we have analyzed CTLA-4 expression and Ipilimumab reactivity on melanoma cell lines and tumor tissues from cutaneous melanoma patients. Then, we investigated whether Ipilimumab can trigger innate immunity in terms of antibody dependent cellular cytotoxicity (ADCC) or Tumor Necrosis Factor (TNF)-α release. Finally, a xenograft murine model was set up to determine in vivo the effects of Ipilimumab and NK cells on melanoma.

Methods

CTLA-4 expression and Ipilimumab reactivity were analyzed on 17 melanoma cell lines (14 primary and 3 long-term cell lines) by cytofluorimetry and on 33 melanoma tissues by immunohistochemistry. CTLA-4 transcripts were analyzed by quantitative RT-PCR. Soluble CTLA-4 and TNF-α were tested by ELISA. Peripheral blood mononuclear cells (PBMC), NK and γδT cells were tested in ADCC assay with Ipilimumab and melanoma cell lines. TNF-α release was analyzed in NK-melanoma cell co-cultures in the presence of ipilimumab. In vivo experiments of xenotransplantation were carried out in NOD/SCID mice. Results were analyzed using unpaired Student’s t-test.

Results

All melanoma cell lines expressed mRNA and cytoplasmic CTLA-4 but surface reactivity with Ipilimumab was quite heterogeneous. Accordingly, about 2/3 of melanoma specimens expressed CTLA-4 at different level of intensity.

Ipilimumab triggered, via FcγReceptorIIIA (CD16), ex vivo NK cells as well as PBMC, IL-2 activated NK and γδT cells to ADCC of CTLA-4⁺ melanoma cells. No ADCC was detected upon interaction with CTLA-4^- FO-1 melanoma cell line. TNF-α was released upon interaction of NK cells with CTLA-4⁺ melanoma cell lines. Remarkably, Ipilimumab neither affected proliferation and viability nor triggered ADCC of CTLA-4⁺ T lymphocytes. In a chimeric murine xenograft model, the co-engraftment of Ipilimumab-treated melanoma cells with human allogeneic NK cells delayed and significantly reduced tumor growth, as compared to mice receiving control xenografts.

Conclusions

Our studies demonstrate that Ipilimumab triggers effector lymphocytes to cytotoxicity and TNF-α release. These findings suggest that Ipilimumab, besides blocking CTLA-4, can directly activate the elimination of CTLA-4⁺ melanomas.

Autoimmune liver disorders and small-vessel vasculitis: four case reports and review of the literature

Autoimmune liver diseases (AILD) are a group of immunologically induced hepatic disorders that can lead to liver cirrhosis and end-stage liver disease. Extra-hepatic involvement and association with rheumatic diseases (such as Sjögren's syndrome, systemic sclerosis and rheumatoid arthritis) are well known, whereas the coexistence of AILD with small-vessel vasculitis in the same patients have been only occasionally reported. In the present paper we report four such cases and an extensive review of the literature. Clinical features of autoimmune-liver diseases associated with small-vessel vasculitis are discussed, as well as possible common pathogenic pathways including HLA genomics, costimulatory molecules and autoantibodies. In conclusion, knowledge about this association can help physicians in recognising and treating an aggressive disease which could otherwise result in severe and multiple organ damage, compromising the overall prognosis and the indication to liver transplantation.

Clinical use of biologics in vasculitis syndromes

Vasculitis syndromes are relative rare conditions but can cause significant mortality and morbidity if not treated adequately. Recent advances in immunosuppressant therapy have radically changed the course of these diseases. However, the standard therapy is not always well tolerated by patients, and some cases are refractory to treatment. New therapeutic possibilities have emerged with the use of so-called "biologics," a new class of genetically engineered drugs used for inflammatory rheumatic diseases, including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis. In the present review, summarized are the most recent data on the efficacy and safety of biologics in the treatment of vasculitis syndromes that cannot be treated with standard therapy.

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.

Altered expression of costimulatory molecules in Behçet's disease according to clinical activity

BACKGROUND

The reduced expression of molecules limiting excessive immune responses has been considered a pathogenic mechanism associated with autoimmune diseases.

OBJECTIVES

To understand the implications of costimulatory molecules in Behçet's disease (BD), the expression of CTLA-4 and PD-1 on T-cell subsets and of their ligands CD80, CD86 and PD-L1 on antigen-presenting cells (APCs) was investigated.

METHODS

Peripheral blood mononuclear cells (PBMC) from 11 patients with active BD, eight patients with inactive BD, eight patients with recurrent aphthous ulcers and 10 healthy volunteers as healthy controls (HC) were stimulated with phorbol myristate acetate and ionomycin. The expression of costimulatory molecules was then analysed by flow cytometry. Soluble CTLA-4 (sCTLA-4) concentrations were determined by enzyme-linked immunosorbent assay and the transcript level of PD-L1 was measured by real-time polymerase chain reaction. The PD-L1 expression in skin lesions of patients with BD was evaluated by immunohistochemistry.

RESULTS

Compared with the HC group, reduced expression of CTLA-4 in CD4+ T cells after stimulation was observed in the active BD group, with no difference in the production of sCTLA-4. CD86 expression, in the resting APCs, was reduced in the active BD group compared with the HC group. PD-L1 expression in the APCs was decreased in the active BD group with or without stimulation of cells. Concordantly, the mRNA levels of PD-L1 in PBMC, and PD-L1 expression in the cutaneous lesions, were low in the active BD group.

CONCLUSIONS

The results of this study suggest that altered expression of PD-L1, CTLA-4 and CD86 may be involved in the pathogenesis of BD.

Pathophysiological importance of antineutrophil antibodies in vasculitis

PURPOSE OF REVIEW

We endeavour to provide a brief overview of the recent advances in understanding of how antineutrophil cytoplasmic antibodies (ANCAs) contribute to the pathophysiology of vasculitis.

RECENT FINDINGS

Substantial progress has been made in our understanding of the immunopathogenesis of ANCA-associated vasculitides. Compelling evidence from in-vitro studies and experimental models in conjunction with clinical trials has confirmed that ANCAs directly contribute to the evolution and progression of the disease process. A new ANCA, directed against human lysosome membrane protein-2 (LAMP-2), has recently been described as a sensitive and specific marker for renal vasculitis and we discuss its potential impact for diagnosis and therapy. Furthermore, high-throughput approaches are starting to identify genetic patterns that may identify patients likely to respond to specific therapy or having a high probability of relapse.

SUMMARY

It has become increasingly clear over the last two decades that ANCA IgG is pathogenic in vasculitis. Novel therapies aimed at selected cell populations or blocking specific pathogenic pathways offer hope for more selectively treating this heterogeneous group of patients, while avoiding nonspecific immunosuppression and its adverse effects.

Recent aspects of vasculitis and future direction

Vasculitis is pathologically identified as specific cellular inflammation, vessel destruction, and tissue necrosis. Current classifications of vasculitis such as the Chapel Hill Classification (CHCC) and American College of Rheumatology (ACR) guidelines are not sufficiently adequate for clinicians to diagnose vasculitis. The biomarkers that are currently in clinical use such as PR3-ANCA and MPO-ANCA, only help in diagnosing small vessel vasculitis and their sensitivity and specificity are not sufficient. However, recent developments related to the pathogenesis and etiopathogenesis of vasculitis have the potential to contribute to new and improved biomarkers. The determination of diverse roles of ANCA and synergistic effects of infection, genetic, environmental factors and drugs on pathogenesis is quite important. The demonstration of a new autoantibody directed to hLAMP-2 and the resemblance to some microbial structures, in addition to the determination of the possible roles of hepatitis B and C on vasculitis are important findings. These hints may lead to new biomarker developments, providing a better method to diagnose vasculitis. The evidence on T cell immunity as circulatory and lesional will likely contribute to the development of new drugs for vasculitis.

Identification of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) isoforms in the Pekin duck

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4, CD152) is an inhibitory T cell receptor predominately expressed on activated T cells. The duck CTLA-4 (DuCTLA-4) cDNA and a transcript lacking the predicted transmembrane encoding region (DuCTLA-4DeltaTM) were isolated from splenocytes using RT-PCR. The predicted DuCTLA-4 protein showed an identity of 92%, 49% and 47% with chicken, human and mouse homologues, respectively. Sequence comparison revealed conservation of residues implicated in the B7 ligand binding, disulfide linkages, glycosylation and intracellular signaling. DuCTLA-4 mRNA was predominately expressed in primary and secondary immune organs. DuCTLA-4 and DuCTLA-4DeltaTM transcripts were differentially regulated in PBMCs. Flow cytometric analysis showed constitutive expression of DuCTLA-4 protein on freshly isolated PBMCs and a modest increase upon mitogen stimulation. Our observations suggest that DuCTLA-4 and its isoform DuCTLA-4DeltaTM evolved before the divergence of birds and mammals. Both DuCTLA-4 isoforms have significant structural homology to mammalian CTLA-4 proteins but their individual roles in the regulation of duck immune responses remains to be elucidated.

Pathogenesis of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of systemic inflammatory vasculitides associated with circulating autoantibodies directed against the neutrophil granule components proteinase 3 and myeloperoxidase. ANCA interact with their target antigens on cytokine primed neutrophils, causing neutrophil activation via several signaling pathways that culminates in endothelial interaction, degranulation, cytokine production, and endothelial and tissue damage. The presence of autoantibodies implies the assistance of autoreactive T-helper cells and B cells, and a failure of regulatory mechanisms. This article reviews the current evidence for the pathogenic mechanisms culminating in autoantibody production, the effects of ANCA-neutrophil and neutrophil-endothelial interactions, and the mechanisms of tissue damage.

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.

The contribution of genetic variation and infection to the pathogenesis of ANCA-associated systemic vasculitis

The aetiology of anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis has not been well defined. Here we review two factors which may play a role in the pathogenesis of the disease: genetics and infection. In particular, we discuss the role of autoantibodies to LAMP-2, which may arise following infection with Gram-negative bacteria, and may contribute to the development of ANCA-associated systemic vasculitis in genetically susceptible individuals.

Confirmation of the genetic association of CTLA4 and PTPN22 with ANCA-associated vasculitis

Background

The genetic contribution to the aetiology of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is not well defined. Across different autoimmune diseases some genes with immunomodulatory roles, such as PTPN22, are frequently associated with multiple diseases, whereas specific HLA associations, such as HLA-B27, tend to be disease restricted. We studied ten candidate loci on the basis of their immunoregulatory role and prior associations with type 1 diabetes (T1D). These included PTPN22, CTLA4 and CD226, which have previously been associated with AAV.

Methods

We genotyped the following 11 SNPs, from 10 loci, in 641 AAV patients using TaqMan genotyping: rs2476601 in PTPN22, rs1990760 in IFIH1, rs3087243 in CTLA4, rs2069763 in IL2, rs10877012 in CYP27B1, rs2292239 in ERBB3, rs3184504 in SH2B3, rs12708716 in CLEC16A, rs1893217 and rs478582 in PTPN2 and rs763361 in CD226. Where possible, we performed a meta-analysis with previous analyses.

Results

Both CTLA4 rs3087243 and PTPN22 rs2476601 showed association with AAV, P = 6.4 × 10^-3 and P = 1.4 × 10^-4 respectively. The minor allele (A) of CTLA4 rs3087243 is protective (odds ratio = 0.84), whereas the minor allele (A) of PTPN22 rs2476601 confers susceptibility (odds ratio = 1.40). These results confirmed previously described associations with AAV. After meta-analysis, the PTPN22 rs2476601 association was further strengthened (combined P = 4.2 × 10^-7, odds ratio of 1.48 for the A allele). The other 9 SNPs, including rs763361 in CD226, showed no association with AAV.

Conclusion

Our study of T1D associated SNPs in AAV has confirmed CTLA4 and PTPN22 as susceptibility loci in AAV. These genes encode two key regulators of the immune response and are associated with many autoimmune diseases, including T1D, autoimmune thyroid disease, celiac disease, rheumatoid arthritis, and now 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.

[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.

Two SNPs in the promoter region of the CTLA-4 gene affect binding of transcription factors and are associated with human myasthenia gravis

OBJECTIVES

The molecular mechanisms underlying the regulation of the CD152 (CTLA-4) gene are largely unknown. Two single nucleotide polymorphisms (SNPs) located in the promoter region are suspected to contribute to the pathogenesis of myasthenia gravis (MG) through regulation of gene expression. SETTING, SUBJECTS AND DESIGN: One hundred and sixty-five unrelated Swedish-Caucasian patients with MG (103 females and 62 males, age 17 to 92 years) and 148 ethnically matched healthy individuals were studied. Gene typing of two SNPs (T/C(-1772) and A/G(-1661)) and quantification of soluble CD152 were performed in the patients. Besides the association studies, the function of these two SNPs is characterized.

RESULTS

We present new genetic associations of two SNPs in the CD152 gene with human MG. These SNPs located in the promoter region are involved in transcriptional binding activity for Nuclear Factor I (NF-1) and c/EBPbeta, as demonstrated using chromatin immunoprecipitation and electromobility shift assay. MG patients with the T/C(-1772) polymorphism have elevated levels of sCD152 in sera.

CONCLUSIONS

The two SNPs in the promoter region are associated with MG and might cause abnormal alternative splicing and affect the expression of CD152, thereby contributing to the pathogenesis of MG.

Therapeutic strategies for systemic necrotizing vasculitides

Treatments of vasculitides have progressed markedly over the past few decades. The first attempts to obtain better-adapted therapeutic strategies evaluated the indications of conventional drugs, and their abilities prolong survival and reduce the number of relapses, while decreasing the severity and number of side effects. Many prospective clinical trials were organized by the French Vasculitis Study Group and the European Vasculitis Study group, and have contributed to optimizing targeted treatment strategies. Recent therapeutic strategies include immunomodulating methods, like plasma exchanges, or products, like intravenous immunoglobulins, or, more recently, new agents called biotherapies. Some of them have achieved promising positive effects, for example, anti-CD20 monoclonal antibodies, and are now being evaluated in prospective trials.

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.

Granulomatose de Wegener

Wegener's granulomatosis is described by the Chapel Hill nomenclature (1994) as a systemic necrotizing vasculitis affecting small to medium-sized vessels. Cytoplasm-labeling antineutrophil cytoplasmic autoantibodies (cANCA) directed against proteinase 3 (PR3) are detected in the sera of approximately 90% of patients. Reported incidence varies from 2 to 12 cases/million inhabitants/year and prevalence from 24 to 157 cases/million inhabitants, depending on the series. While still rare, incidence seems to have increased slightly over the past few decades. Most new cases involve adults aged 45-60 years. Many of the immune mechanisms involved in its pathogenesis have been identified. These involve cANCA as well as neutrophils, various lymphocyte subtypes, activation molecules, and cytokines. Genetic and environmental factors have been observed in some cases. However, the precise causes of the disease and of the initial immune process leading to cANCA production remain unknown. The most characteristic clinical manifestations are involvement of the upper and lower respiratory tracts and glomerulonephritis. Diffuse/systemic forms may be clinically distinguished from localized/limited forms: the former are mainly associated with vasculitis, and the latter with granulomatous inflammation. Diagnosis relies largely on the combination of characteristic clinical symptoms and cANCA anti-PR3, but histological confirmation should always be obtained when biopsy of affected organs is feasible and safe. Kidney biopsy is particularly useful in cases with renal manifestations, because it also provides some prognostic information. Current recommendations for treatment of systemic forms call first for an induction phase that combines corticosteroids and intravenous cyclophosphamide; the first three pulses are given every 2 weeks and then every 3 weeks until remission is achieved, followed by a maintenance phase with a less toxic immunosuppressant. The optimal duration of this regimen has not yet been determined, but it must certainly not be less than 18 months. Continuation of cotrimoxazole for two additional years is advised once immunosuppressants have been withdrawn. Remission is obtained in more than 85% of the cases to date, but the high relapse rate remains a matter of concern: approximately half of all patients will relapse within the five years following diagnosis. Promising new therapeutic agents, including rituximab, anti-TNF-alpha, and abatacept, are currently under evaluation and may substantially modify management of this disease in the years to come. Today, however, they are reserved for refractory cases.

Indications for biotherapy in systemic vasculitides

Biotherapy now holds a specific place in the therapeutic armamentarium for systemic vasculitides. Such therapy includes cytokines, such as (pegylated) alpha-interferon for hepatitis B virus-related polyarteritis nodosa and hepatitis C virus-related cryoglobulinemic vasculitis, and polyvalent immunoglobulin (IVIg), with well-defined indications and pending positive results. More specifically targeted monoclonal antibodies include antitumor necrosis factor-alpha or anti-CD20 for antineutrophil cytoplasmic antibody-associated vasculitides or anti-interleukin-5 and anti-IgE for Churg-Strauss syndrome. However, the exact indications of these latter new agents, as well as their optimal dosage and duration, are not defined. Therefore, they are prescribed mainly for patients with disease refractory to conventional therapy, in whom results are promising. Results of international ongoing trials will determine whether the agents may also have a place as first-line treatment.

A suggestive association of fuchs heterochromic cyclitis with cytotoxic T cell antigen 4 gene polymorphism

BACKGROUND

Fuchs heterochromic cyclitis (FHC) is a chronic inflammatory eye disease, usually presenting as unilateral anterior uveitis. Up to date no disease susceptibility genes have been described for FHC.

METHODS

The allele frequency of HLA DRB1 and DQB1, polymorphisms of the tumour necrosis factor (TNF) alpha promoter region (-376, -308, -238), the promoter (-318), first exon (+49) and (AT)n repeat polymorphism of the cytotoxic T cell antigen 4 (CTLA4) gene were analysed in 44 FHC patients and 139 healthy controls.

RESULTS

The CTLA4 -318 C/T genotype was increased in FHC patients [odds ratio (OR) 3.0, 95% confidence interval (CI) 1.4-6.5], as well as long CTLA4 (AT)n microsatellite alleles with more than 16 AT repeats (OR 2.6, 95% CI 1.3-5.3). A trend towards the -308 G/A TNF-alpha genotype was found in the patient cohort, whereas no difference in HLA class II allele distribution was observed.

CONCLUSION

CTLA4 but not TNF-alpha or HLA class II DRB1 and DQB1 may represent a candidate gene for disease susceptibility in FHC.

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.

Characterization of the expanded T-cell populations in patients with Wegener's granulomatosis

OBJECTIVES

Wegener's granulomatosis (WG) is a chronic inflammatory disease characterized by granulomatosis inflammation, systemic vasculitis and glomerulonephritis. In patients, the peripheral T cells are characterized by mono/oligoclonal CD4+/CD8+ T-cell AV/BV receptor expansions, with aberrant expression of activation markers. This study was designed to characterize the phenotypic differences between the expanded and nonexpanded T-cell populations. Expression of markers for activation, costimulation and adhesion molecules was examined. As earlier studies have shown aberrant expression of CD28/CD152, we also analysed the expression of another costimulatory system, the tumour necrotic factor receptor (TNFR) superfamily proteins.

DESIGN

Fluorocrome-conjugated monoclonal antibodies and flow cytometry was used to analyse the expression of the different markers on the surface of the expanded and nonexpanded subsets of T cells.

SETTING

The Karolinska Hospital and Karolinska Institutet in Stockholm, Sweden.

SUBJECTS

Nine patients with WG (six men and three women) had 16 TCRAV/BV CD4+/CD8+ expanded populations that were characterized.

RESULTS

The expanded TCRA/BV CD4+ and CD8+ cells had lower percentages of cells expressing CD28 and higher of those expressing CD152 (CTLA-4). The expanded CD4+ population had more cells expressing HLA-DR, CD57 and CCR5 (CD195), whilst the expression of CD25 was present on fewer of the expanded cells. The expanded CD8+ population contained more cells expressing CD137 (4-1BB), CD137 (4-1BBL), CD30 (Ki-1), CD40 and CD134 (OX40).

CONCLUSIONS

There were marked differences in the phenotypes of expanded and nonexpanded T-cell populations.

Antineutrophil cytoplasmic antibodies

Much like other autoantibodies (eg, anti-double stranded DNA in systemic lupus erythematosus or antiglomerular basement membrane antibodies in Goodpasture's syndrome), antineutrophil cytoplasmic antibodies (ANCA) have provided doctors with a useful serological test to assist in diagnosis of small-vessel vasculitides, including Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and their localised forms (eg, pauci-immune necrotising and crescentic glomerulonephritis). 85-95% of patients with Wegener's granulomatosis, microscopic polyangiitis, and pauci-immune necrotising and crescentic glomerulonephritis have serum ANCA. ANCA directed to either proteinase 3 or myeloperoxidase are clinically relevant, yet the relevance of other ANCA remains unknown. Besides their diagnostic potential, ANCA might be valuable in disease monitoring. In addition, data seem to confirm the long-disputed pathogenic role of these antibodies. Present treatments for ANCA-associated vasculitis are not free from side-effects and as many as 50% of patients relapse within 5 years. Accurate understanding of the key pathogenic points of ANCA-associated vasculitis can undoubtedly provide a more rational therapeutic approach.

Wegener’s granulomatosis: Is biologic therapy useful?

Wegener's granulomatosis (WG) is a complex autoimmune disorder that has been transformed from a uniformly lethal process to a chronic disease with a relapsing-remitting course. In the setting of frequent relapses, the need to manage cumulative disease damage and drug toxicities has spurred the identification and development of new potent and directed therapies. Biologic agents, which offer the potential for remission-induction and drug-sparing approaches to treat WG, have been studied in several small, open-label clinical series and one large, randomized, placebo-controlled clinical trial. This article discusses the results of these trials and the potential of these biologic agents to treat WG.