The cellular signature of urinary immune cells in Lupus nephritis: new insights into potential biomarkers

INTRODUCTION

Urinary T cells represent a reliable noninvasive biomarker for proliferative Lupus nephritis (LN). Little is known about the presence of T cell subsets, B cells and macrophages in the urine although they may further improve the validity of urinary cellular biomarkers for LN.

METHODS

We analyzed contemporaneous blood and urine samples of patients with active LN (n = 19), other Systemic Lupus Erythematosus (SLE) patients (n = 79) and urine samples of patients with diabetic nephropathy (DN; n = 14) and anti-neutrophil cytoplasmatic antibody (ANCA) associated vasculitis (AAV; n = 11) by flow cytometry.

RESULTS

Numbers of urinary T cells, B cells and macrophages correlated with disease activity and were significantly higher in the active LN group. Urinary T cells showed excellent distinction of patients with active LN, CD8+ T cells (AUC of ROC = 1.000) and CD4+ T cells (AUC = 0.9969) alike. CD19+ B cells (AUC = 0.7823) and CD14+ macrophages (AUC = 0.9066), as well as the clinical standard proteinuria (AUC = 0.9201), failed to reach these high standards. Patients with DN or AAV also showed increased urinary cell counts, although the CD4/CD8-ratio was significantly lower in SLE compared to in DN (p = 0.0006). Urinary CD4+ T cells of active LN patients proved to be mainly of effector memory phenotype and expressed significantly more CD40L and ki67 than corresponding blood cells. Urinary Treg counts correlated with disease activity.

CONCLUSIONS

Despite of detectable urinary cell counts for B cells and macrophages, T cells remain the best urinary cellular biomarker for LN. A low CD4/CD8-ratio seems to be characteristic for LN.

The protein tyrosine phosphatase PTP1B is a negative regulator of CD40 and BAFF-R signaling and controls B cell autoimmunity

The protein tyrosine phosphatase PTP1B regulates co-receptor signaling on B cells and thus controls B cell autoimmunity.

Tyrosine phosphorylation of signaling molecules that mediate B cell activation in response to various stimuli is tightly regulated by protein tyrosine phosphatases (PTPs). PTP1B is a ubiquitously expressed tyrosine phosphatase with well-characterized functions in metabolic signaling pathways. We show here that PTP1B negatively regulates CD40, B cell activating factor receptor (BAFF-R), and TLR4 signaling in B cells. Specifically, PTP1B counteracts p38 mitogen-activated protein kinase (MAPK) activation by directly dephosphorylating Tyr¹⁸² of this kinase. Mice with a B cell–specific PTP1B deficiency show increased T cell–dependent immune responses and elevated total serum IgG. Furthermore, aged animals develop systemic autoimmunity with elevated serum anti-dsDNA, spontaneous germinal centers in the spleen, and deposition of IgG immune complexes and C3 in the kidney. In a clinical setting, we observed that B cells of rheumatoid arthritis patients have significantly reduced PTP1B expression. Our data suggest that PTP1B plays an important role in the control of B cell activation and the maintenance of immunological tolerance.

Cell-specific type I IFN signatures in autoimmunity and viral infection: what makes the difference?

Gene expression profiling of peripheral blood mononuclear cells (PBMCs) has revealed a crucial role for type I interferon (IFN) in the pathogenesis of systemic lupus erythematosus (SLE). However, it is unclear how particular leucocyte subsets contribute to the overall type I IFN signature of PBMCs and whole blood samples.Furthermore, a detailed analysis describing the differences in the IFN signature in autoimmune diseases from that observed after viral infection has not been performed to date. Therefore, in this study, the transcriptional responses in peripheral T helper cells (CD4⁺) and monocyte subsets (CD16⁻ inflammatory and CD16⁺ resident monocytes) isolated from patients with SLE, healthy donors (ND) immunised with the yellow fever vaccine YFV-17Dand untreated controls were compared by global gene expression profiling.It was striking that all of the transcripts that were regulated in response to viral exposure were also found to be differentially regulated in SLE, albeit with markedly lower fold-change values. In addition to this common IFN signature, a pathogenic IFN-associated gene signature was detected in the CD4⁺ T cells and monocytes from the lupus patients. IL-10, IL-9 and IL-15-mediated JAK/STAT signalling was shown to be involved in the pathological amplification of IFN responses observed in SLE. Type I IFN signatures identified were successfully applied for the monitoring of interferon responses in PBMCs of an independent cohort of SLE patients and virus-infected individuals. Moreover, these cell-type specific gene signatures allowed a correct classification of PBMCs independent from their heterogenic cellular composition. In conclusion, our data show for the first time that monocytes and CD4 cells are sensitive biosensors to monitor type I interferon response signatures in autoimmunity and viral infection and how these transriptional responses are modulated in a cell- and disease-specific manner.

Urinary CD4 T cells identify SLE patients with proliferative lupus nephritis and can be used to monitor treatment response

OBJECTIVES

Proliferative lupus nephritis (LN) is one of the major concerns in the treatment of systemic lupus erythematosus (SLE). Here we evaluate urinary CD4 T cells as a biomarker of active LN and indicator of treatment response.

METHODS

Urinary CD3CD4 T cells were quantified using flow cytometry in 186 urine samples from 147 patients with SLE. Fourteen patients were monitored as follow-up. Thirty-one patients with other nephropathies and 20 healthy volunteers were included as controls.

RESULTS

In SLE, urinary CD4 T cell counts ≥800/100 ml were observed exclusively in patients with active LN. Receiver operator characteristic analysis documented clear separation of SLE patients with active and non-active LN (area under the curve 0.9969). All patients with up-to-date kidney biopsy results showing proliferative LN had high urinary CD4 T cell numbers. In patients monitored under therapy, normalisation of urinary CD4 T cell counts indicated lower disease activity and better renal function. In contrast, patients with persistence of, or increase in, urinary T cells displayed worse outcomes.

CONCLUSIONS

Urinary CD4 T cells are a highly sensitive and specific marker for detecting proliferative LN in patients with SLE. Furthermore, monitoring urinary CD4 T cells may help to identify treatment responders and treatment failure and enable patient-tailored therapy in the future.

IFNα and its response proteins, IP-10 and SIGLEC-1, are biomarkers of disease activity in systemic lupus erythematosus

OBJECTIVES

To evaluate and compare the clinical efficacy of three biomarkers for interferon (IFN) activity (measured directly and indirectly) and six traditional biomarkers in indicating current and prospective disease activity (DA) in systemic lupus erythematosus (SLE).

METHODS

IFNα (dissociation-enhanced lanthanide fluorescent immunoassay), IFNγ-inducible protein 10 (IP-10) (ELISA) and sialic acid-binding Ig-like lectin 1 (SIGLEC-1) (flow cytometry) were measured in 79 accurately characterised patients with lupus and compared with serum titres of Anti-dsDNA (ELISA and radioimmunoassay), Anti-dsDNA-NcX ELISA, Anti-Nuc ELISA, and complement C3 and C4. DA was evaluated using the British Isles Lupus Assessment Group 2004 Index (BILAG-2004) and a modified SLE Disease Activity Index-2000 (mSLEDAI-2K). In addition, 31 clinically quiescent patients were monitored for flares over the course of 180 days.

RESULTS

Increased levels of IFNα, IP-10 and SIGLEC-1 were found in 32%, 50% and 86%, respectively, of 66 patients with active SLE. IFNα (r=0.45; p<0.0001) and SIGLEC-1 (r=0.54; p<0.0001) correlated better with BILAG-2004 than did IP-10 (r=0.38; p=0.0002), Farr assay (r=0.40; p=0.0001), Anti-dsDNA-NcX ELISA (r=0.28; p=0.0061), Anti-dsDNA ELISA (r=0.31; p=0.0025), Anti-Nuc ELISA (r=0.25; p=0.0121), C3 (r=-0.43; p<0.0001) and C4 (r=-0.33; p=0.0013). Predictors of SLE flares were disease duration ≤92 months, mild clinical activity (in contrast with no activity), complement C3≤89 mg/dl and IFNα≥20 pg/ml, while only lymphocyte count and age were independent predictors in multivariate analysis.

CONCLUSIONS

IFNα, IP-10 and SIGLEC-1 emerged as beneficial biomarkers of DA in patients with SLE. Therefore the implementation of IFN biomarkers in standard lupus diagnostics should be reappraised, especially in view of emerging anti-IFN-directed therapies.

The multifaceted balance of TNF-α and type I/II interferon responses in SLE and RA: how monocytes manage the impact of cytokines

Many cytokines are involved in the pathogenesis of autoimmune diseases and are recognized as relevant therapeutic targets to attenuate inflammation, such as tumor necrosis factor (TNF)-α in rheumatoid arthritis (RA) and interferon (IFN)-α/γ in systemic lupus erythematosus (SLE). To relate the transcriptional imprinting of cytokines in a cell type- and disease-specific manner, we generated gene expression profiles from peripheral monocytes of SLE and RA patients and compared them to in vitro-generated signatures induced by TNF-α, IFN-α2a, and IFN-γ. Monocytes from SLE and RA patients revealed disease-specific gene expression profiles. In vitro-generated signatures induced by IFN-α2a and IFN-γ showed similar profiles that only partially overlapped with those induced by TNF-α. Comparisons between disease-specific and in vitro-generated signatures identified cytokine-regulated genes in SLE and RA with qualitative and quantitative differences. The IFN responses in SLE and RA were found to be regulated in a STAT1-dependent and STAT1-independent manner, respectively. Similarly, genes recognized as TNF-α regulated were clearly distinguishable between RA and SLE patients. While the activity of SLE monocytes was mainly driven by IFN, the activity from RA monocytes showed a dominance of TNF-α that was characterized by STAT1 down-regulation. The responses to specific cytokines were revealed to be disease-dependent and reflected the interplay of cytokines within various inflammatory milieus. This study has demonstrated that monocytes from RA and SLE patients exhibit disease-specific gene expression profiles, which can be molecularly dissected when compared with in vitro-generated cytokine signatures. The results suggest that an assessment of cytokine-response status in monocytes may be helpful for improvement of diagnosis and selection of the best cytokine target for therapeutic intervention.

[DNA microarrays]

Since their development in the 1990s DNA microarrays have advanced to one of the most important technologies for biomedical research. Miniaturization enables up to 1 million different sequence-specific DNA hybridization tests to be performed on an area of less than 2 cm². Depending on the selection of oligonucleotide sequences, which are assembled on a microarray and on the treatment of samples prior to hybridization, up to genome-wide analyses for genotypes, gene expression, epigenetic changes or promoter activation can be performed. Increasing knowledge about the human genome advances commercial pre-assembly of DNA microarrays with selected oligonucleotide sequences for specialized applications. In clinical rheumatology gene expression analyses in treatment studies are of increasing importance. Similarly, this technique also identified new biomarkers that allow even better assessment of the current disease activity. The varieties of application enable the possibility of systematic research on the immunological response to specific patterns after stimulation. This opens up opportunities to detect and differentiate immunological reaction patterns better.

Diagnostic value and clinical laboratory associations of antibodies against recombinant ribosomal P0, P1 and P2 proteins and their native heterocomplex in a Caucasian cohort with systemic lupus erythematosus

Introduction

In this study, we sought to determine the diagnostic value and clinical laboratory associations of autoantibodies against recombinant ribosomal P0, P1 and P2 proteins and their native heterocomplex in systemic lupus erythematosus (SLE).

Methods

Autoantibodies against recombinant ribosomal P proteins (aRibP_R0, aRibP_R1 and aRibP_R2) and antibodies against native ribosomal P heterocomplex (aRibP_NH) were determined in sera from patients with SLE (n = 163), systemic sclerosis (n = 66), Sjögren's syndrome (n = 54), rheumatoid arthritis (n = 90) and healthy donors (n = 100) using enzyme-linked immunosorbent assay. Test results were correlated to medical records, including the American College of Rheumatology criteria, the Systemic Lupus Erythematosus Disease Activity Index 2000, laboratory data and medications of all SLE patients.

Results

Sensitivities of 22.0% for aRibP_R0, 14.9% for aRibP_R2, 14.3% for aRibP_NH and 10.7% for aRibP_R1 were obtained at a specificity of 99%. The assay for aRibP_R0 detection demonstrated the best performance in receiver-operating characteristics analysis, with aRibP_R0 detectable in 10% of anti-Smith antibody and anti-double-stranded DNA-negative sera at a specificity of 100%. ARibP_R0 positivity was associated with lymphocytopenia. ARibP_R1⁺ patients had significantly higher γ-glutamyl transpeptidase (GGT) levels than their aRibP_R1^- counterparts. No specific damage occurred in aRibP⁺ lupus patients compared with a group of age-, sex- and nephritis-matched aRibP^- lupus patients within 3 years.

Conclusions

The determination of antibodies against ribosomal P proteins improves the diagnosis of SLE and should therefore be implemented in upcoming criteria for the diagnosis or classification of SLE. High titers of aRibP_R0 can be associated with lymphocytopenia, and high titers of aRibP_R1 can be associated with elevated GGT levels. So far, there is no evidence for a prognostic value of aRibPs for damage.

Anti-dsDNA-NcX ELISA: dsDNA-loaded nucleosomes improve diagnosis and monitoring of disease activity in systemic lupus erythematosus

INTRODUCTION

The objective of this study was to compare the clinical usefulness of the new anti-double-stranded DNA nucleosome-complexed enzyme-linked immunosorbent assay (Anti-dsDNA-NcX ELISA), which is based on dsDNA-loaded nucleosomes as antigens, with established test systems based on dsDNA or nucleosomes alone for systemic lupus erythematosus (SLE) diagnostics and determination of disease activity.

METHODS

Sera from a cohort of 964 individuals comprising 207 SLE patients, 357 disease controls and 400 healthy donors were investigated using the Anti-dsDNA-NcX ELISA, Farr assay, Anti-dsDNA ELISA, Anti-nucleosome ELISA and Crithidia luciliae immunofluorescence (CLIF) assay, all of which are tests available from EUROIMMUN Medizinische Labordiagnostika AG (Lübeck, Germany). Receiver operating characteristic curve analyses were performed to compare the sensitivity and specificity of each assay. The test results yielded by these assays in a group of 165 fully characterized SLE patients were compared with the corresponding medical records.

RESULTS

The Anti-dsDNA-NcX ELISA was found to have a sensitivity of 60.9% and a specificity of 98.9% in all 964 individuals at the manufacturer's cutoff of 100 U/ml. At a comparable specificity of 99%, the sensitivity amounted to 59.9% for the Anti-dsDNA-NcX ELISA, 54.1% for the Farr assay, 53.6% for the antinucleosome ELISA and 35.8% for the anti-dsDNA ELISA. The CLIF assay had a sensitivity of 28.0% and a specificity of 98.2%. The Anti-dsDNA-NcX ELISA correlated mostly with global disease activity in a cross-sectional analysis. In a longitudinal analysis of 20 patients with 69 patient visits, changes in Anti-dsDNA-NcX ELISA and antinucleosome ELISA results correlated highly with changes in disease activity over time.

CONCLUSIONS

The use of dsDNA-complexed nucleosomes as antigens in ELISA leads to optimized determination of diagnosis and disease activity in SLE patients and is available for clinical practice.

Blood dendritic cells in systemic lupus erythematosus exhibit altered activation state and chemokine receptor function

BACKGROUND

Dendritic cells (DCs) have a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). Reduced numbers of blood DCs and the accumulation of DCs at inflammatory sites have been observed in SLE. One crucial feature of DCs is their ability to migrate.

OBJECTIVE

To analyse the maturation/activation state and the migratory capacity of different DC precursor subsets in SLE to further elucidate their role in autoimmunity.

METHODS

Plasmacytoid DCs (pDCs), myeloid DCs (mDCs) and monocytes from patients with SLE, healthy volunteers and healthy volunteers immunised with tetanus/diphtheria were examined by flow cytometry for expression of subset-specific antigens (BDCA-2, CD11c, CD14, HLA-DR), activation/maturation markers (CD83, CD86, CD40, BLyS) and chemokine receptors (CCR1, CCR5, CCR7, ChemR23). Additionally, migratory capacity to chemokine receptors was investigated in vitro using the chemokines RANTES, CCL19 and chemerin.

RESULTS

SLE monocytes and mDCs had higher CD86 and B-lymphocyte stimulatory factor (BLyS) expression levels. ChemR23 expression was lower in SLE pDCs and mDCs. Basal and CCL19-specific migration levels were higher in SLE pDCs. Altered DC function in SLE had no correlative changes in chemokine receptor expression, whereas immunisation-induced blood DC migration patterns in healthy donors were accompanied by changes in chemokine receptor expression.

CONCLUSIONS

The phenotypic and migratory disturbances observed in SLE blood DCs could result in altered distribution of DCs in peripheral tissues, contributing to dysregulated immune responses and autoimmunity.

[Systemic lupus erythematosus. Target criteria for treatment]

Systemic lupus erythematosus (SLE) is a chronic systemic intermittent autoimmune disease, which can affect nearly all organ systems. The disease is characterized by the detection of more than 100 different auto-antibodies. For the clinical practice as well as in controlled clinical studies it is absolutely necessary to define target criteria which allow the evaluation of the effectiveness of therapy. Many instruments are available for measuring the activity of the disease, the quality of life, the extent of irreversible damage and the individual manifestation in organs. There are also now various biomarkers to characterize the pathophysiologic aspects, clinical activity, therapeutic effectiveness and prognosis.

From transcriptome to cytome: integrating cytometric profiling, multivariate cluster, and prediction analyses for a phenotypical classification of inflammatory diseases

Gene expression studies of peripheral blood cells in inflammatory diseases revealed a large array of new antigens as potential biomarkers useful for diagnosis, prognosis, and therapy stratification. Generally, their validation on the protein level remains mainly restricted to a more hypothesis-driven manner. State-of-the-art multicolor flow cytometry make it attractive to validate candidate genes at the protein and single cell level combined with a detailed immunophenotyping of blood cell subsets. We developed multicolor staining panels including up to 50 different monoclonal antibodies that allowed the assessment of several hundreds of phenotypical parameters in a few milliliters of peripheral blood. Up to 10 different surface antigens were measured simultaneously by the combination of seven different fluorescence colors. In a pilot study blood samples of ankylosing spondylitis (AS) patients were compared with normal donors (ND). A special focus was set on the establishment of suitable bioinformatic strategy for storing and analyzing hundreds of phenotypical parameters obtained from a single blood sample. We could establish a set of multicolor stainings that allowed monitoring of all major leukocyte populations and their corresponding subtypes in peripheral blood. In addition, antigens involved in complement and antibody binding, cell migration, and activation were acquired. The feasibility of our cytometric profiling approach was demonstrated by a successful classification of AS samples with a reduced subset of 80 statistically significant parameters, which are partially involved in antigen presentation and cell migration. Furthermore, these parameters allowed an error-free prediction of independent AS and ND samples originally not included for parameter selection. This study demonstrates a new level of multiparametric analysis in the post-transcriptomic era. The integration of an appropriate bioinformatic solution as presented here by the combination of a custom-made Access database along with cluster- and prediction-analysis tools predestine our approach to promote the human cytome project.