Can lupus flares be associated with tuberculosis infection?

Tuberculosis mimicking the onset of systemic lupus erythematosus flare: Case based review

AIM

To analyze the clinical features of lupus-like tuberculosis (TB).

METHODS

Three cases of TB imitating systemic lupus erythematosus (SLE) flare were collected in our hospital. Based on literature review, there are only 3 reports of TB resembling lupus flare rather than SLE per se.

RESULTS

The 3 cases of lupus mimickers, with a mean age of 30.3 years, ranging from 27 to 32 years, had atypical features of SLE, namely no typical butterfly erythema, lupus hair, alopecia or proteinuria, similar to the patients reported in the 3 previously mentioned studies. Emergence of different autoantibodies like anti-nuclear antibodies, anti-double-stranded DNA, anti-nucleosome antibodies, and anti-histone antibodies could occur in TB, mostly as an epiphenomenon. In patients with specific serological anti-Sm and hypocomplementemia, active TB cannot be easily ruled out. The presence of autoantibodies neither altered the clinical manifestations and radiographic findings of active TB, nor were detectable after infections are resolved. The resistance of the SLE manifestations to the steroid and immunosuppressive treatment suggests the contribution of an infectious disease.

CONCLUSION

TB stimulated the production of autoantibodies, with shared affinity for mycobacteria and human antigens, which may have led to lupus mimickers.

Immune dysregulation and pathogenic pathways mediated by common infections in rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the world's most prevalent inflammatory autoimmune diseases, affecting between 0.4 and 1.3% of the population. The susceptibility to RA appears to be influenced by a complex interaction between a favorable genetic background and the existence of a specific immune reaction against a wide range of environmental variables. Among the known environmental variables, infections are believed to have a significant role in promoting the formation of autoimmune disorders, which are frequently caused by specific microorganisms. Infections have been linked to RA in recent medical studies. In this study, we selected the most prevalent infections associated with RA from the literature and described the data confirming their pathogenic role in RA. Our investigation included Mycobacterium, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Proteus mirabilis, Epstein-Barr virus, parvovirus, and Prevotella copri.

A Case of Previously Undiagnosed Systemic Lupus Erythematosus and Mycobacterium tuberculosis Infection Presenting as Diffuse Alveolar Hemorrhage

Diffuse alveolar hemorrhage (DAH) is described as the collection of blood in alveolar spaces caused by damaged pulmonary vasculature. It often presents as a life-threatening medical emergency that requires urgent medical intervention along with timely diagnosis and management of the underlying cause. We hereby report a 19-year-old female who presented with clinical and radiological characteristics consistent with DAH. Laboratory workup studies revealed a diagnosis of systemic lupus erythematosus (SLE) as well as Mycobacterium tuberculosis (MTB) infection. This report describes an extremely unusual case of undiagnosed SLE and coexistent tuberculosis presenting as DAH. This leads to an interesting possibility of risks in patients with immune-mediated vasculitis towards developing severe pulmonary disease in the setting of pulmonary mycobacterial infection.

Tuberculosis remains a major burden in systemic lupus erythematosus patients in Durban, South Africa

Objective

Infections are common in systemic lupus erythematosus (SLE), with tuberculosis (TB) being important in an endemic environment. We studied the prevalence and spectrum of TB in SLE in Durban, South Africa.

Methods

A medical records review of SLE patients seen over 13-year period, and the demographic data, clinical manifestations, laboratory findings, treatment and outcome were noted.

Results

There were 512 SLE patients and 72 (14.1%) had TB. Thirty (41.7%) had pulmonary TB (PTB) and 42 (58.3%) had extra-pulmonary TB (EPTB). The prevalence of TB among the different ethnic groups was 36/282 (12.8%) for Indian people, 29/184 (15.8%) Black African people, 7/26 (26.9%) admixed African people and none among the 18 White people. Comparison of the 72 SLE-TB patients with 72 SLE controls showed no difference in gender, age at SLE diagnosis and disease duration. The SLE-TB patients had a significant increase in the clinical and laboratory features of disease activity (arthritis, mucocutaneous lesions, renal involvement, vasculitis, low complement, raised ds-DNA antibodies), and cumulative prednisone use over the preceding 3 months.Compared to PTB, the EPTB patients were significantly younger, developed TB earlier after SLE diagnosis, and had higher disease activity. The EPTB patients also had increase in features of disease activity (renal, thrombocytopenia, ds-DNA antibodies), and increase in ever use of intravenous methylprednisolone (IV-MP) and mycophenolate mofetil (MMF). On multivariate analysis, the independent risk factors for EPTB were ever use of MMF (p = 0.003) and IV-MP (p = 0.027). Analysis of the cumulative SLE criteria showed renal involvement was an independent risk factor for EPTB. The outcome was similar in both groups.

Conclusion

We show an increased prevalence of TB (14.1%) and EPTB (58.3%) in SLE in an endemic area and confirm that features of disease activity and use of immunosuppressive therapy are the major risk factors. Renal involvement (as a cumulative criterion) is an independent risk factor for EPTB.

Tuberculosis-associated hemophagocytic lymphohistiocytosis misdiagnosed as systemic lupus erythematosus: A case report

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder with rapid progression and high mortality. HLH occurs mostly due to infection, malignant tumors, and immune disorders. Among infections that cause HLH, viral infections, especially Epstein-Barr virus infections, are common, whereas tuberculosis is rare. Tuberculosis-associated HLH has a wide range of serological and clinical manifestations that are similar to those of systemic lupus erythematosus (SLE).

CASE SUMMARY

This study describes a case of tuberculosis-associated HLH misdiagnosed as SLE because of antinuclear antibody (ANA), Smith (Sm) antibody and lupus anticoagulant positivity; leukopenia; thrombocytopenia; pleural effusion; decreased C3, quantitatively increased 24 h urinary protein and fever. The patient was initially treated with glucocorticoids, which resulted in peripheral blood cytopenia and symptom recurrence. Then, caseating granulomas and hemophagocytosis were observed in her bone marrow. She was successfully treated with conventional category 1 antituberculous drugs. In addition, we reviewed the literature on tuberculosis-associated HLH documented in PubMed, including all full-text articles published in English from December 2009 to December 2019, and summarized the key points, including the epidemiology, clinical manifestations, diagnosis, and treatment of tuberculosis-associated HLH and the differences of the present case from previous reports.

CONCLUSION

Tuberculosis should be considered in patients with fever or respiratory symptoms. Antituberculous drugs are important for treating tuberculosis-associated HLH.

Clinical spectrum of active tuberculosis in patients with systemic lupus erythematosus

INTRODUCTION

There is paucity of data on tuberculosis in Indian patients with systemic lupus erythematosus (SLE). We retrospectively studied clinical features and outcome of tuberculosis in SLE.

METHODS

Medical records of patients who developed tuberculosis simultaneous or after the diagnosis of SLE were retrospectively reviewed. All patients fulfilled 1997 ACR and/or SLICC 2012 classification criteria for SLE. A diagnosis of tuberculosis required bacteriological, histopathological or CT/MRI suggestive of tuberculosis and initiation of four drug antituberculous therapy. Baseline parameters were compared with the rest of cohort to identify predictors of tuberculosis.

RESULTS

In our cohort of 1335 SLE patients, 48 (3.6%) developed tuberculosis. Incidence of tuberculosis was calculated to be 733 per 100,000 patient years and occurred after a mean disease duration of 3.0 ± 4.1 years. Extrapulmonary tuberculosis (n = 37) was commoner than pulmonary tuberculosis (n =11). Most common radiological pattern in pulmonary tuberculosis was miliary and musculoskeletal TB was most common extrapulmonary TB. A microbiological diagnosis was obtained in 52.1% patients. Male gender was associated with higher risk of tuberculosis [OR 3.30 (1.55-7.05)]. Mortality was 14.5% and all patients who died had either disseminated (n = 5) or central nervous system (CNS) tuberculosis (n = 2).

CONCLUSION

Incidence of tuberculosis in SLE is higher than general population and is associated with different phenotype and higher mortality. Male gender was associated with increased risk of tuberculosis in SLE.

Role of Infections in the Pathogenesis of Rheumatoid Arthritis: Focus on Mycobacteria

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease characterized by chronic erosive polyarthritis. A complex interaction between a favorable genetic background, and the presence of a specific immune response against a broad-spectrum of environmental factors seems to play a role in determining susceptibility to RA. Among different pathogens, mycobacteria (including Mycobacterium avium subspecies paratuberculosis, MAP), and Epstein–Barr virus (EBV), have extensively been proposed to promote specific cellular and humoral response in susceptible individuals, by activating pathways linked to RA development. In this review, we discuss the available experimental and clinical evidence on the interplay between mycobacterial and EBV infections, and the development of the immune dysregulation in RA.

Prednisolone dose during treatment of tuberculosis might be a risk factor for mortality in patients with systemic lupus erythematosus: a hospital-based cohort study

Patients with systemic lupus erythematosus (SLE) are at high risk of tuberculosis (TB) because of their immunocompromised status and the use of immunosuppressive drugs. In endemic regions, TB complicates the diagnosis and treatment of SLE, but the risk factors of mortality in these patients have not been investigated. In this study, we reviewed medical records during 2006–2016. Patients who fulfilled the 1997 American College of Rheumatology SLE criteria and presented with definite TB were enrolled. The primary outcome was mortality during TB treatment. There were 5388 SLE patients screened, and 30 patients were enrolled. Seven patients died during follow-up. Compared with the survival group, patients in the mortality group had significantly more central nervous system involvement of TB, higher Systemic Lupus Erythematosus Disease Activity Index-2000 scores and more cyclophosphamide use before TB, and higher prednisolone dose before and during TB treatment. Cox regression showed that prednisolone dose during TB treatment was an independent risk factor for mortality (per 10 mg/day increase, hazard ratio (HR) 1.61, p = .019). For SLE patients, prednisolone dose during TB treatment is an independent risk factor for mortality. Keeping prednisolone dose at less than 25 mg per day during TB treatment might be a reasonable strategy in these patients.

Miliary tuberculosis mimicking systemic lupus erythematosus flare

A 26-year-old woman was diagnosed with and treated for systemic lupus erythematosus (SLE) in 2002. She was admitted 11 years later with nephrotic-range proteinuria and lupus nephritis and received two doses of rituximab after failing on steroids and mycophenolate mofetil. Four months later, she presented with fever and joint pain/swelling. Gram stains, joint aspirates, and blood culture all yielded negative results for bacteria. She was discharged after treatment for a possible flare of lupus, but two weeks later, she presented again with a cough and shortness of breath in addition to the flare symptoms. Synovial fluid Smears, and cultures yielded positive results for Mycobacterium tuberculosis; similarly, sputum polymerase chain reaction test and culture confirmed pulmonary tuberculosis. Tuberculosis is difficult to diagnose in SLE patients; it may present like or precipitate SLE flare. In this patient a presumed SLE flare turned out to be an aggressive miliary, disseminated tuberculosis.

Mycobacterium tuberculosis: An Adaptable Pathogen Associated With Multiple Human Diseases

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), is an extremely successful pathogen that adapts to survive within the host. During the latency phase of infection, M. tuberculosis employs a range of effector proteins to be cloud the host immune system and shapes its lifestyle to reside in granulomas, sophisticated, and organized structures of immune cells that are established by the host in response to persistent infection. While normally being restrained in immunocompetent hosts, M. tuberculosis within granulomas can cause the recrudescence of TB when host immunity is compromised. Aside from causing TB, accumulating evidence suggests that M. tuberculosis is also associated with multiple other human diseases, such as pulmonary complications, autoimmune diseases, and metabolic syndromes. Furthermore, it has been recently appreciated that M. tuberculosis infection can also reciprocally interact with the human microbiome, which has a strong link to immune balance and health. In this review, we highlight the adaptive survival of M. tuberculosis within the host and provide an overview for regulatory mechanisms underlying interactions between M. tuberculosis infection and multiple important human diseases. A better understanding of how M. tuberculosis regulates the host immune system to cause TB and reciprocally regulates other human diseases is critical for developing rational treatments to better control TB and help alleviate its associated comorbidities.

Pp65 antigenemia and cytomegalovirus diagnosis in patients with lupus nephritis: report of a series

Introduction:

In contrast to organ transplantation, few studies correlate the monitoring of pp65 antigenemia with a diagnosis of cytomegalovirus (CMV) in patients with systemic lupus erythematosus (SLE).

Objective:

To highlight the importance of CMV outside transplantation, we monitored pp65 antigenemia in a series of SLE patients.

Methods:

From March 2015 to March 2016, SLE patients presenting kidney involvement, fever, and an unclear infection at hospital admission were monitored through pp65 antigenemia. The pp65 antigenemia assay, revealed by immunofluorescence, was correlated with clinical and laboratory findings.

Results:

We included 19 patients with a suspected unclear infection. A positivity for pp65 antigenemia was found in seven patients (36.8%). The mean age was 33.5 ± 11.2 years, 16 (84%) were females, and 16 (84%) were black. Lymphopenia, anemia, and higher scores of SLEDAI were significantly more common in pp65-positive patients. Five patients received antiviral therapy with ganciclovir. Although receiving specific CMV treatment, one patient died because of suspected CMV disease.

Conclusions:

Pp65 antigenemia might be relevant in SLE patients, and studies with a greater number of patients are needed in order to establish sensitivity and specificity of pp65 antigenemia in different clinical contexts of SLE patients.

Disseminated tuberculosis masquerading as a presentation of systemic lupus erythematosus

Tuberculosis (TB) infection is the endemic in Asia-Pacific region. Miliary TB is a disseminated form which may present similarly as autoimmune conditions. Here we describe a 17-year-old girl who had miliary TB with manifestations mimicking new-onset systemic lupus erythematosus (SLE) including oral ulcers, serositis, cytopenia, proteinuria and raised autoantibody titers. Complex associations between SLE and TB are highlighted. High index of clinical suspicion for TB infection is needed upon presentations resembling immune diseases like SLE.

Tuberculous monoarthritis of the wrist in a patient with systemic lupus erythematosus: a case report

Background

Unusual forms of tuberculosis are common among immune-suppressed patients, leading to challenges in diagnosis and management. We present a Sri Lankan patient with systemic lupus erythematosis, investigated for chronic wrist pain with low inflammatory markers and without systemic symptoms, who was subsequently diagnosed to have tuberculosis of the joint.

Case presentation

A 31-year-old woman with systemic lupus erythematosis in remission was evaluated for chronic left wrist pain without significant examination findings on presentation. She did not have any constitutional symptoms. Basic investigations did not reveal any significant abnormalities. She was treated with increasing immunosuppression as for lupus related arthritis. Subsequently she developed a wrist effusion with high inflammatory markers, and was treated as septic arthritis. Synovial biopsy features suggested tuberculosis. The patient’s symptoms improved with surgical intervention and anti-tuberculosis treatment.

Conclusion

Tuberculosis should be considered in patients with systemic arthritis with unusual symptoms. Delayed diagnosis along with continuing immunosuppression can lead to extensive tissue damage. Clinically detectable effusions should be analyzed along with synovial biopsy in order to exclude concurrent infections. Radiography of the joint has poor sensitivity to detect early joint damage, but changes may be evident early on magnetic resonance imaging, sothis should be considered in patients with unusual features.

The risk of tuberculosis in SLE patients from an Asian tertiary hospital

Systemic lupus erythematosus (SLE) has been associated with increased risk of tuberculosis (TB). However, little is known about the extent and risk factors for TB among Asian patient with SLE. We aimed to assess the rate of TB in patients with SLE, and investigate the risk of SLE on TB development using hospital administrative database. This is an historical cohort study of hospital discharge database from 2004 to 2011 to identify cases with SLE and TB using International Statistical Classification of Diseases and Related Health Problems, 9th Revision, Australian Modification (ICD-9-AM) codes. Of 301568 hospitalized patients, 841 (0.3%) patients had SLE, 1843 (0.6%) patients had TB, including 17 SLE patients (2.0%). SLE patients had a significantly higher rate of TB (2.0 vs. 0.6%, p < 0.001) compared to that of patients without SLE. The differences in the higher rate after breaking down was in the pulmonary TB group (1.7 vs. 0.5%, p < 0.00) but not in extrapulmonary TB group (0.4 vs. 0.1%, p = 0.060). Logistic regression analyses showed that SLE was a significant and independent predictor of TB (odds ratio 4.6, 95% CI 2.8-7.5, p < 0.001) after adjustment for factors such as age group, gender, ethnicity, admission class, nutritional deficiency, organ transplantation, and Charlson comorbidity index. SLE patients were found to experience higher rates of tuberculosis in this group of Asian patient population. Patients with SLE should be considered as a high-risk group for TB, active screening for latent patients and treatment for positive TB patients is needed.

SLE and Tuberculosis: A Case Series and Review of Literature

Systemic Lupus Erythematosus (SLE) and Tuberculosis (TB) are intricately related with an increase in the risk of TB in SLE. Primary mechanisms pertaining to the increased susceptibility for TB are the inherent immunodeficient state of SLE and use of immunosuppressant agents in the treatment of SLE. We report a case series of five female patients of SLE with TB who presented between January 2015 and December 2015 in a tertiary care teaching hospital in North Eastern India. All the patients were young to middle aged females having SLE with or without lupus nephritis who were on immunosuppressive therapy with corticosteroids, mycophenolate mofetil or cyclophosphamide. Two of the cases had sputum positive pulmonary tuberculosis while rest had Extra-Pulmonary TB (EPTB). The response to anti-tubercular therapy led to clinical improvement in all the cases except one who had an adverse outcome. Our series further substantiates the increased risk of TB in SLE thus, prompting further research towards better management of these two disease entities in conjunction.

Lupus and leprosy: beyond the coincidence

Systemic lupus erythematous (SLE) is an autoimmune disease that presents an increased susceptibility to infections which may trigger reactivation. Disease flares have been mostly associated with parvovirus B19, cytomegalovirus, EBV and Mycobacterium tuberculosis infections, but it is probable that many other agents may also induce innate and adaptive immune system stimulation including the production of autoantibodies as ANA, anti nDNA and anti-ß2-GPI mainly in lepromatous leprosy. Mycobacterium leprae not only may determine symptoms that mimic lupus flares, including autoantibodies production, but could also act as a trigger for lupus reactivation; however, its association is still not fully explored. As demonstrated for tuberculosis, it is quite possible that molecular mimicry may also be involved in the interface of these two diseases. Some studies reported shared epitopes among idiotypes derived from 8E7 and TH9 lepromatous antibodies and those obtained from SLE patients, and it could partially explain the triggering phenomenon of SLE caused by M. leprae. We report and discuss three Brazilian patients whose disease was inactive and presented disease flares concurrently with the diagnosis of leprosy.

Mycobacteria and autoimmunity

Mycobacterial infections can cause a variety of different manifestations. The increasing incidence of these infections worldwide brought another medical dilemma: immunological manifestations characterized by the presence of many autoantibodies and concomitant presence of autoimmune diseases. The burden of tuberculosis reactivation that emerged with immunosuppressive therapy worsened with the growing use of biological disease-modifying antirheumatic drugs (DMARDs). This review will address the relationship between the immune system and mycobacteria.

Novel pebbles in the mosaic of autoimmunity

Almost 25 years ago, the concept of the 'mosaic of autoimmunity' was introduced to the scientific community, and since then this concept has continuously evolved, with new pebbles being added regularly. We are now looking at an era in which the players of autoimmunity have changed names and roles. In this issue of BMC Medicine, several aspects of autoimmunity have been addressed, suggesting that we are now at the forefront of autoimmunity science. Within the environmental factors generating autoimmunity are now included unsuspected molecules such as vitamin D and aluminum. Some adjuvants such as aluminum are recognized as causal factors in the development of the autoimmune response. An entirely new syndrome, the autoimmune/inflammatory syndrome induced by adjuvants (ASIA), has been recently described. This is the new wind blowing within the branches of autoimmunity, adding knowledge to physicians for helping patients with autoimmune disease.

Associations between selected immune-mediated diseases and tuberculosis: record-linkage studies

BACKGROUND

Previous studies have suggested that there may be an association between some immune-mediated diseases and risk of tuberculosis (TB).

METHODS

We analyzed a database of linked statistical records of hospital admissions and death certificates for the whole of England (1999 to 2011), and a similar database (the Oxford Record Linkage Study (ORLS)) for a region of southern England in an earlier period. Rate ratios for TB were determined, comparing immune-mediated disease cohorts with comparison cohorts.

RESULTS

In the all-England dataset, there were significantly elevated risks of TB after hospital admission for the following individual immune-mediated diseases: Addison's disease, ankylosing spondylitis, autoimmune hemolytic anemia, chronic active hepatitis, coeliac disease, Crohn's disease, dermatomyositis, Goodpasture's syndrome, Hashimoto's thyroiditis, idiopathic thrombocytopenia purpura (ITP), myasthenia gravis, myxedema, pemphigoid, pernicious anemia, polyarteritis nodosa, polymyositis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren's syndrome, systemic lupus erythematosus (SLE), thyrotoxicosis and ulcerative colitis. Particularly high levels of risk were found for Addison's disease (rate ratio (RR) = 11.9 (95% CI 9.5 to 14.7)), Goodpasture's syndrome (RR = 10.8 (95% CI 4.0 to 23.5)), SLE (RR = 9.4 (95% CI 7.9 to 11.1)), polymyositis (RR = 8.0 (95% CI 4.9 to 12.2)), polyarteritis nodosa (RR = 6.7 (95% CI 3.2 to 12.4)), dermatomyositis (RR = 6.6 (95% CI 3.0 to 12.5)), scleroderma (RR = 6.1 (95% CI 4.4 to 8.2)) and autoimmune hemolytic anemia (RR = 5.1 (95% CI 3.4 to 7.4)).

CONCLUSIONS

These two databases show that patients with some immune-mediated diseases have an increased risk of TB, although we cannot explicitly state the direction of risk or exclude confounding. Further study of these associations is warranted, and these findings may aid TB screening, control and treatment policies.

The future of autoimmunity

There have been enormous strides in our understanding of autoimmunity. These strides have come under the umbrellas of epidemiology, immunological phenotype and function, disease definitions and classification and especially new therapeutic reagents. However, while these advances have been herculean, there remains enormous voids. Some of these voids include genetic susceptibility and the interaction of genes and environment. The voids include induction of tolerance in preclinical disease and definitions of host susceptibility and responses to the expensive biologic agents. The voids include the so-called clustering of human autoimmune diseases and the issues of whether the incidence is rising in our western society. Other voids include the relationships between microbiology, vaccination, gut flora, overzealous use of antibiotics, and the role of nanoparticles and environmental pollution in either the induction or the natural history of disease. One cannot even begin to address even a fraction of these issues. However, in this special issue, we are attempting to discuss clinical issues in autoimmunity that are not usually found in generic reviews. The goal is to bring to the readership provocative articles that ultimately will lead to improvement in patient care.

Tuberculosis Is Not a Risk Factor for Primary Biliary Cirrhosis: A Review of the Literature

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterised serologically by cholestasis and the presence of high-titre antimitochondrial antibodies, and histologically by chronic nonsuppurative cholangitis and granulomata. As PBC is a granulomatous disease andMycobacterium tuberculosisis the most frequent cause of granulomata, a causal relation between tuberculosis and PBC has been suggested. Attempts to find serological evidence of PBC-specific autoantibodies such as AMA have been made and, conversely, granulomatous livers from patients with PBC have been investigated for molecular evidence ofMycobacterium tuberculosis. This paper discusses in detail the reported data in support or against an association betweenMycobacterium tuberculosisinfection and PBC. We discuss the immunological and microbiological data exploring the association of PBC with exposure toMycobacterium tuberculosis. We also discuss the findings of large epidemiologic studies investigating the association of PBC with preexistent or concomitant disorders and the relevance of these findings with tuberculosis. Genome-wide association studies in patients with tuberculosis as well as in patients with PBC provide conclusive hints regarding the assumed association between exposure to this mycobacterium and the induction of PBC. Analysis of these data suggest thatMycobacterium tuberculosisis an unlikely infectious trigger of PBC.

Down-regulated NOD2 by immunosuppressants in peripheral blood cells in patients with SLE reduces the muramyl dipeptide-induced IL-10 production

BACKGROUND

Pattern recognition receptors (PRRs) such as Toll-like receptors are aberrantly expressed of peripheral blood mononuclear cells (PBMCs) in systemic lupus erythematosus (SLE) patients, for playing immunopathological roles.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the expression and function of the PRR nucleotide-binding oligomerization domain (NOD2) in SLE. NOD2 expression in T, B lymphocytes, monocytes, myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs) was assessed in SLE patients and healthy controls (HCs) using flow cytometric analysis. Ex vivo production of cytokines from PBMCs upon NOD2 agonist muramyl dipeptide (MDP) stimulation was assessed using Cytometric Bead Array. Over-expression of NOD2 in monocytes was observed in immunosuppressant naïve SLE patients, and was positively associated with longer disease duration. Immunosuppressive therapy was an independent explanatory variable for downregulating NOD2 expression in CD8+ T, monocytes, mDCs and pDCs. Ex vivo basal productions of cytokines (IL-6, IL-8 and IL-10) were significantly increased in immunosuppressant naïve patients and patients with active disease despite immunosuppressants compared with HCs. Upon MDP stimulaiton, relative induction (%) of cytokines (IL-1β) from PBMC was significantly increased in immunosuppressant naïve patients with inactive disease, and patients with active disease despite immunosuppressant treatment compared with HCs. Immunosuppressant usage was associated with a decreased basal production and MDP induced relative induction (%) of IL-10 in patients with inactive disease compared with immunosuppressant naïve patients and HCs.

CONCLUSIONS/SIGNIFICANCE

Bacterial exposure may increase the NOD2 expression in monocytes in immunosuppressant naïve SLE patients which can subsequently lead to aberrant activation of PBMCs to produce proinflammatory cytokines, implicating the innate immune response for extracellular pathogens in the immunopathological mechanisms in SLE. Immunosuppressant therapy may downregulate NOD2 expression in CD8+ T lymphocytes, monocytes, and DCs in SLE patients which subsequently IL-10 reduction, contributing towards the regulation of immunopathological mechanisms of SLE, at the expense of increasing risk of bacterial infection.