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ObjectiveTreatment-refractory antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a life-threatening condition without evidence-based treatment options. One emerging treatment option for several antibody-mediated autoimmune diseases is the anti-CD38 antibody daratumumab, which depletes autoantibody-secreting plasma cells.MethodsWe treated two patients with severe life-threatening AAV with renal and pulmonary manifestation despite induction therapy with rituximab and cyclophosphamide with four to eight doses of 1800 mg daratumumab. We followed clinical and immunological responses.ResultsThe first patient with myeloperoxidase-ANCA-positive microscopic polyangiitis had resolution of pneumonitis and pleuritis and stabilisation of kidney function after daratumumab. The second patient with proteinase 3-ANCA-positive granulomatosis with polyangiitis, diffuse alveolar haemorrhage necessitating extracorporeal membrane oxygenation (ECMO) and acute kidney failure, requiring kidney replacement therapy, was weaned off ECMO, mechanical ventilation and dialysis and discharged home after daratumumab. Clinical improvement was paralleled by a strong reduction in serum ANCA levels as well as total IgG, indicating depletion of plasma cells. Apart from the depletion of CD38+natural killer cells, blood leucocyte levels were not notably influenced by daratumumab. Only mild adverse events, such as hypogammaglobulinaemia and an upper respiratory tract infection occurred.ConclusionDaratumumab was safe and effective in inducing remission in two patients with severe treatment-refractory AAV, warranting prospective clinical trials to establish safety and efficacy.

Objective To evaluate the safety and effects of irinotecan, an inhibitor of topoisomerase I, on refractory lupus nephritis. Method A patient with refractory lupus nephritis under medication with mycophenolic acid, prednisolone, and hydroxychloroquine was treated with add-on low-dose irinotecan. Irinotecan was applied every fourth week at a dose of 50 mg/m2 for four cycles followed by 100 mg/m2 for another eight cycles. Renal function and anti-double-stranded DNA antibodies as well as blood count for evaluation of side effects were assessed during the treatment with irinotecan. Results Before starting the treatment with irinotecan, a urine protein/creatinine ratio of 1298 mg/g was determined. This declined to 613 mg/g after four cycles with 50 mg/m2 irinotecan and was further reduced to 198 mg/g when using the higher dose of irinotecan. Kidney function remained stable, with creatinine levels of 1.66 mg/dL at the beginning and 1.76 mg/dL at the end of treatment with irinotecan. Importantly, no side effects, such as diarrhoea or neutropenia, were observed during the entire course of treatment. Conclusion Administration of low-dose irinotecan as add-on medication for the treatment of refractory lupus nephritis was shown to be safe. Clinical trials are needed to determine whether irinotecan can improve kidney function and the outcome of patients with refractory lupus nephritis.

Summary Background An acquired deficiency of interleukin-2 (IL-2) and related defects in regulatory T cell homeostasis are thought to play a crucial role in the pathogenesis of systemic lupus erythematosus. We hypothesised that reconstitution of regulatory T-cell homoeostasis with low doses of IL-2 would be beneficial to patients with systemic lupus erythematosus. Methods In this uncontrolled, phase 1 and 2a trial done in the Department of Rheumatology and Clinical Immunology at Charite—University Medicine Berlin (Berlin, Germany), we assessed the safety and tolerability of low-dose recombinant human IL-2 (aldesleukin) and its effects on regulatory T cells. We recruited patients aged 18–75 years with a confirmed diagnosis of systemic lupus erythematosus and moderate-to-severe disease activity despite previous treatment with at least two conventional therapies. Patients were given four cycles of low-dose aldesleukin daily for 5 days followed by a 9–16 day rest. The primary endpoints were safety and the number of patients who achieved at least a 100% increase in the proportion of CD25hi-expressing cells among circulating CD3 + CD4 + FOXP3 + CD127lo regulatory T cells at day 62 (ie, after four treatment cycles). Secondary endpoints included disease activity as measured by the Safety of Estrogens in Lupus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI) and the British Isles Lupus Assessment Group (BILAG) score, disease flares as measured by the SLEDAI flare index, auto-antibody and complement concentrations at day 62. Exploratory endpoints included various cellular and immunological parameters. The trial is registered with WHO/ICTRP, number DRKS00004858. Findings Between March 31, 2014, and May 27, 2016, 13 patients were screened, of whom ten met eligibility criteria and were enrolled in the trial. Two additional patients were treated between April 1, 2013, and March 11, 2014, in a compassionate use setting. Eleven (92%) of the 12 patients achieved the primary endpoint. 159 adverse events were recorded, 75 (47%) of which were treatment related. Most treatment-related adverse events were transient and mild to moderate (grade 1–2). The most common adverse event was injection-site reaction (20%). No serious adverse events occurred during the treatment period. In ten (83%) of 12 patients, SELENA-SLEDAI scores were lower at day 62 than at baseline, and no severe disease flares were observed during the treatment period. Decreased disease activity correlated with the magnitude of increase in the proportion of activated regulatory T cells. IL-2 treatment resulted in a preferential proliferation of regulatory T cells that retained suppressive capacity. We observed decreases in cells that are involved in the regulation of germinal-centre reactions. Interpretation Low-dose IL-2 therapy is safe and well tolerated and selectively promotes the expansion of functional regulatory T cells in patients with moderate-to-severe systemic lupus erythematosus. Low-dose IL-2 treatment might also be beneficial in reducing disease activity, although larger trials are needed to address efficacy. Funding German Research Foundation.

Objectives To evaluate and compare the diagnostic accuracy of SIGLEC1, a surrogate marker of type I IFN, with established biomarkers in an inception cohort of systemic lupus erythematosus (SLE). Methods SIGLEC1 was analysed by flow cytometry in 232 patients referred to our institution with suspected SLE between October 2015 and September 2020. Results SLE was confirmed in 76 of 232 patients (32.8 %) according to the 2019 EULAR/ACR classification criteria and their SIGLEC1 values were significantly higher compared with patients without SLE (P 99.9 % and 0.1 %, respectively. Using receiver operating characteristic (ROC) analysis and DeLong testing, the area under the curve (AUC) for SIGLEC1 (AUC = 0.95) was significantly higher than for ANA (AUC = 0.88, P = 0.031), C3 (AUC = 0.83, P = 0.001) and C4 (AUC = 0.83, P = 0.002) but not for anti-dsDNA antibodies (AUC = 0.90, P = 0.163). Conclusion IFN-I pathway activation is detectable in almost all newly diagnosed SLE patients. Thus, a negative test result for SIGLEC1 is powerful to exclude SLE in suspected cases.

In the search for anti-renal autoreactivity in human lupus nephritis, we stimulated blood-derived CD4+ T cells from patients with systemic lupus erythematosus with various kidney lysates. Although only minor responses were detectable, these experiments led to the development of a search algorithm that combined autoantibody association with human lupus nephritis and target gene expression in inflamed kidneys. Applying this algorithm, five potential T cell antigens were identified. Blood-derived CD4+ T cells were then stimulated with these antigens. The cells were magnetically enriched prior to measurement with flow cytometry to facilitate the detection of very rare autoantigen-specific cells. The detected responses were dominated by IFN-γ-producing CD4+ T cells. Additionally, IL-10-producing CD4+ T cells were found. In a next step, T cell reactivity to each single antigen was independently evaluated with T cell libraries and [3H]-thymidine incorporation assays. Here, Vimentin and Annexin A2 were identified as the main T cell targets. Finally, Vimentin reactive T cells were also found in the urine of three patients with active disease. Overall, our experiments show that antigen-specific CD4+ T cells targeting renally expressed antigens arise in human lupus nephritis and correlate with disease activity and are mainly of the Th1 subset.

Background:While there have been advances in the therapy of systemic lupus erythematosus (SLE) in recent years, there have been no major new findings in SLE biomarkers [1, 2]. Type I interferon (IFN) plays a pivotal role in the pathogenesis of SLE [3]. In 2008, we first described CD169 / SIGLEC-1 (sialic acid-binding immunoglobulin-like lectin-1), an interferon-induced adhesion molecule on monocytes in SLE patients [4]. For over five years SIGLEC-1 has been routinely assessed in our clinic.Objectives:To evaluate and compare the diagnostic utility of the type I IFN induced SIGLEC-1 with established biomarkers in the initial diagnosis of the disease.Methods:We analyzed retrospectively 232 patients who were on suspicion of SLE at Charité University Hospital Berlin between October 2015 and September 2020. Patients underwent full clinical characterization, and biomarkers were determined in the routine laboratory. Based on the final diagnosis, we divided patients into two groups: A) initial diagnosis of SLE and B) Non-SLE mimicking condition.Results:In 76 patients (32.3 %) SLE was confirmed by fulfilling the EULAR / ACR 2019 classification criteria [5]. SIGLEC-1 was dramatically increased in patients with an initial diagnosis of SLE compared to patients without SLE (p 99.9 % and 0.2 %. We further aimed to compare not only the performance of the tests at a given cutoff but also across all possible measured values. Therefore, we conducted ROC curves analyses (see figure 1). The area under the curve (AUC) of SIGLEC-1 test was significantly higher than that of ANA test (AUC=0.88, p=0.031), C3 (AUC = 0.83, p=0.001), C4 (AUC=0.83, p=0.002), but not than that of the Anti-dsDNA ELISA (AUC=0.90, p=0.163).Conclusion:Our study shows that IFN activity is a hallmark at the onset of the disease and that the interferon biomarker SIGLEC-1 is valuable to rule out SLE in suspected cases.References:[1]Ostendorf L, Burns M, Durek P, Heinz GA, Heinrich F, Garantziotis P, Enghard P, Richter U, Biesen R, Schneider U et al: Targeting CD38 with Daratumumab in Refractory Systemic Lupus Erythematosus. N Engl J Med 2020, 383(12):1149-1155.[2]Furie R, Rovin BH, Houssiau F, Malvar A, Teng YKO, Contreras G, Amoura Z, Yu X, Mok CC, Santiago MB et al: Two-Year, Randomized, Controlled Trial of Belimumab in Lupus Nephritis. N Engl J Med 2020, 383(12):1117-1128.[3]Ronnblom L, Leonard D: Interferon pathway in SLE: one key to unlocking the mystery of the disease. Lupus Sci Med 2019, 6(1):e000270.[4]Biesen R, Demir C, Barkhudarova F, Grun JR, Steinbrich-Zollner M, Backhaus M, Haupl T, Rudwaleit M, Riemekasten G, Radbruch A et al: Sialic acid-binding Ig-like lectin 1 expression in inflammatory and resident monocytes is a potential biomarker for monitoring disease activity and success of therapy in systemic lupus erythematosus. Arthritis Rheum 2008, 58(4):1136-1145.[5]Aringer M, Costenbader K, Daikh D, Brinks R, Mosca M, Ramsey-Goldman R, Smolen JS, Wofsy D, Boumpas DT, Kamen DL et al: 2019 European League Against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus. Annals of the Rheumatic Diseases 2019, 78(9):1151-1159.[6]Brinks R, Fischer-Betz R, Sander O, Richter JG, Chehab G, Schneider M: Age-specific prevalence of diagnosed systemic lupus erythematosus in Germany 2002 and projection to 2030. Lupus 2014, 23(13):1407-1411.Disclosure of Interests:None declared

Background:We recently reported the beneficial clinical responses of the anti-CD38 monoclonal antibody daratumumab in two patients with systemic lupus erythematosus (SLE) [1]. While the primary rationale for its use was the depletion of autoantibody-producing long-lived plasma cells, daratumumab may promote additional therapeutic effects on CD38-expressing T cells, but their origin, lifestyle and role in lupus pathophysiology remains elusive.Objectives:To investigate the phenotype, transcriptional program, functional properties and clinical associations of CD4+ and CD8+CD38+ memory T cells in SLE compared to healthy controls (HC).Methods:CD38-expression on memory T cell subsets was measured by flow cytometry in 65 patients with SLE and 28 healthy controls. We investigated the functional capacity of CD38+ T cells using CFSE staining and intracellular cytokine staining after polyclonal stimulation. Additionally, we performed single-cell transcriptome and T-cell-receptor sequencing of 7 SLE patients and 7 matched healthy controls, including surface protein expression analysis using CITE-seq (RNA-barcoded) antibodies.Results:Compared to healthy controls, the frequency of CD38-expressing memory T cells in SLE was significantly increased in both CD4+ and CD8+ T cells. SLE patients with a previous or current lupus nephritis had significantly increased levels of CD8+CD38+ memory T cells compared to those without history of renal involvement. CD38+ memory T cells expressed increased levels of Ki-67 and displayed higher proliferative capacity upon polyclonal stimulation than their CD38- counterparts, both in SLE patients and HC, while they showed decreased ability to secrete IFN-γ, IL-2, GM-CSF and TNF-α. Single-cell transcriptome sequencing revealed that CD8+CD38+ memory T cells were enriched within terminally differentiated, cytotoxic CD8 T cells, and had reduced TCR repertoire diversity compared to their CD38- counterparts. CD8+CD38+ memory T cells from SLE patients had significantly higher expression of type I interferon associated genes, both compared to CD38- memory T cells from SLE patients and CD38+ cells from HCs.Conclusion:CD38+ memory T cells with increased proliferative capacity but altered effector functions are significantly expanded in peripheral blood of SLE and correlate with the lupus nephritis. Although the factors mediating their generation and their precise role in the disease pathophysiology remain to be investigated, CD38-expressing T cells may be useful as a future biomarker for lupus nephritis.References:[1]Ostendorf L, Burns M, Durek P, Heinz GA, Heinrich F, Garantziotis P, et al. Targeting CD38 with Daratumumab in Refractory Systemic Lupus Erythematosus. N Engl J Med. 2020 Sep 17;383(12):1149–55.[2]Katsuyama E, Suarez-Fueyo A, Bradley SJ, Mizui M, Marin AV, Mulki L, et al. The CD38/NAD/SIRTUIN1/EZH2 Axis Mitigates Cytotoxic CD8 T Cell Function and Identifies Patients with SLE Prone to Infections. Cell Reports. 2020 Jan;30(1):112-123.e4.Acknowledgements:We thank our patients and healthy controls for making our research possible.Disclosure of Interests:None declared.

Background:ANCA-associated vasculitis (AAV) causes necrotizing crescentic glomerulonephritis (NCGN) which is a major contributor to morbidity and mortality in AAV. Since therapy relies on cytotoxic agents with potentially severe adverse effects, a reliable non-invasive biomarker of disease activity is needed to determine the right balance between over- and undertreatment. Using the urine space as a window into the local inflammatory milieu of the kidney, quantification of urinary leukocytes using flow cytometry has become an upcoming marker of various other inflammatory kidney diseases. As recent studies have illuminated the emerging role of T regulatory (Treg) and Th17 cells in the pathogenesis of AAV, these could represent a viable non-invasive biomarker more closely displaying the underlying pathogenic processes than metabolites or epiphenomena of inflammation.Objectives:To quantify urinary T cells in active renal AAV and asses their biomarker characteristics.Methods:Using flow cytometry, T-lymphocytes and their subsets were quantified in peripheral blood and urine samples from patients with active AAV with or without NCGN, in stable remission with previous NCGN and healthy controls. Concentrations of urinary soluble metabolites and cytokines (Monocyte-attracting protein 1 (MCP-1), sCD163, sCD25 and C5a) were measured using Multiplex analysis. Results were verified in a separate validation cohort.Results:Patients with renal active AAV (n = 30) showed significantly higher urinary cell counts of total T cells, CD4+, CD8+, Treg and Th17 subsets than disease (n = 21) and healthy controls (n = 8). Patients with active renal AAV also showed a significantly higher percentage of Tregs in urine than in blood. While Tregs allowed a robust discrimination between active renal AAV and disease controls (receiver operator characteristics (ROC): area under the curve (AUC) 0.93, sensitivity 79%, specificity 95%) quantification of all T cells proved to be slightly more accurate (ROC: AUC 0.95, sensitivity 92%, specificity 95%). Soluble markers showed a slightly inferior discrimination (MCP-1 ROC: AUC 0.90, sensitivity 60%, specificity 100%, sCD163 ROC: AUC 0.92, sensitivity 96%, specificity 85%) while sCD25 and C5a were far less accurate.Conclusion:Urinary T cells are significantly elevated in active renal AAV and the increased frequency of Tregs in urine suggests active migration into inflamed glomeruli and thereby the urine rather than mere bleeding of ruptured capillaries. These cells show great potential for a non-invasive biomarker close to the local inflammatory milieu. Particularly the total count of urinary T cells showed slightly superior biomarker characteristics than previously established soluble markers. Further studies are needed to confirm these results and show potential prognostic value of these cellular markers.Disclosure of Interests:None declared

Background:Plasma Cells (PCs) are implicated in the pathogenesis of Systemic Lupus erythematosus (SLE) and their targeting proved a promising treatment modality. As there is a monoclonal therapeutic antibody targeting CD38 licensed for clinical use in multiple myeloma, plasma cell depletion via CD38 seems to represent a promising path in SLE treatment. While CD38 Is highly expressed on plasmacells, it is present on the surface of subsets of T and B lymphocytes as well as myeloid cells.Objectives:Here we aim to identify the differential expression of CD38 on peripheral blood leukocytes in SLE compared to healthy controls (HC) investigate the function of CD38+ T lymphocytesMethods:We performed flow cytometry to investigate the expression of CD38 on peripheral blood mononuclear cells of SLE patients (n=36) and HCs (n=20). We additionally analyzed the expression of T lymphocytes within the urine of patients with lupus nephritis as well as the skin of SLE patients. We investigated the inflammatory potential of CD38 positive memory T lymphocytes after stimulation and performed single-cell RNA sequencing analyses.Results:CD38 Expression is increased on certain immune cell subsets: Plasmablasts and unswitched Memory B cells, as well as plasmacytoid dendritic cells and CD16+ non-classical monocytes. We observed a drastic increase CD38 in both memory CD4 and CD8 T lymphocytes in SLE patients. These cells were mostly effector T cells (and not regulatory T cells) and expressed other markers of T cell activation and proliferation. We found an enrichment of CD38+ memory T cells in the urine of patients with lupus nephritis. After polyclonal stimulation of T cells, CD38+ produced less inflammatory cytokines. Preliminary single-cell sequencing results indicate that CD38+ CD8+ T-lymphocytes have decreased clonal diversity and that these cells express genes associated with exhaustion and type 1 interferon response.Conclusion:Increased CD38 expression on various lymphocyte subsets provides an additional rationale for investigating CD38-directed therapies in SLE. Targeting CD38 could not only deplete plasma cells but also has the potential to target interferon alpha producing plasmacytoid dendritic cells and modulate inflammatory T cell functions.Disclosure of Interests:Lennard Ostendorf: None declared, Philipp Enghard: None declared, Pawel Durek: None declared, Frederik Heinrich: None declared, Mir-Farzin Mashreghi: None declared, Gerd Rüdiger Burmester Consultant of: AbbVie Inc, Eli Lilly, Gilead, Janssen, Merck, Roche, Pfizer, and UCB Pharma, Speakers bureau: AbbVie Inc, Eli Lilly, Gilead, Janssen, Merck, Roche, Pfizer, and UCB Pharma, Andreas Radbruch: None declared, Falk Hiepe: None declared, Tobias Alexander: None declared

Background:Depletion of long-lived plasma cells (PC) resembles a novel concept for the treatment of antibody-mediated autoimmune diseases, such as systemic lupus erythematosus (SLE). Therapeutic approaches such as autologuos stem-stem cell transplantation and proteasome inhibition are limited by significant treatment-related toxicity. A novel target for PC depletion is CD38, a surface protein that is highly expressed on plasma cells (PCs) but also activated T-cells and most myeloid cells. Daratumumab is a monoclonal antibody targeting CD38 that is licensed for the treatment of multiple myeloma.Objectives:Here, we aimed to ascertain clinical safety and efficacy of Daratumumab for the treatment of refractory SLE, as well as to gain insights into effects of Daratumumab on the immune system.Methods:We treated two SLE patients with life- and organ-threatening SLE with four weekly dosis of 16 mg/kg Daratumumab. We performed integrative analyses of clinical, serological and immunological effects over a follow-up period of 6 months. Using flow cytometry and single-cell RNA and T-cell receptor sequencing we followed CD38 expression and composition of peripheral blood leukocytes with a special focus on memory T cells.Results:Patient 1, a 50-year old woman, suffered from active biopsy-proven class III lupus nephritis (LN) with nephrotic syndrome, pericarditis, arthritis and skin rash. Upon Daratumumab treatment, her glomerular filtration rate normalized within 3 months and proteinuria gradually declined from 6.4 to 1.9g/g Creatinine during the 180-day follow-up period. Pericarditis, arthritis and skin rash completely resolved. Patient 2, a 32-year-old woman, presented with autoimmune hemolytic anemia requiring blood transfusions, immune thrombocytopenia and cutaneous vasculitis. Her direct antiglobulin test normalized within 3 months and remained negative throughout follow-up with consecutive recovery of the hemolytic anemia. Immune thrombocytopenia stabilized and vasculitic skin lesions completely resolved. Infusions were well tolerated without severe adverse drug reactions. NK cells and Dendritic Cells were transiently depleted, while numbers of T cells, B cells and Monocytes in the peripheral blood remained stable. CD38+ memory T cells that were expanded prior to treatment were virtually undetectable early after treatment. Their single cell transcriptomics demonstrated an upregulation of genes associated with activation, cytotoxicity and type 1 interferon response. CD38+ CD8+ memory T-cells showed marked oligoclonality. These prominent clones persisted upon treatment but their transcription profile gradually normalized.Conclusion:Daratumumab appears to be a safe and effective treatment for refractory SLE. Further investigations are warranted to establish the efficacy in a clinical trial and to gain further insights into the pathophysiologic mechanism of action.Disclosure of Interests:Lennard Ostendorf: None declared, Udo Schneider: None declared, Marie Urbicht: None declared, Philipp Enghard: None declared, Frederik Heinrich: None declared, Pawel Durek: None declared, Gitta Heinz: None declared, Henrik Mei: None declared, Mir-Farzin Mashreghi: None declared, Gerd Rüdiger Burmester Consultant of: AbbVie Inc, Eli Lilly, Gilead, Janssen, Merck, Roche, Pfizer, and UCB Pharma, Speakers bureau: AbbVie Inc, Eli Lilly, Gilead, Janssen, Merck, Roche, Pfizer, and UCB Pharma, Andreas Radbruch: None declared, Falk Hiepe: None declared, Tobias Alexander: None declared

Objectives Defects in regulatory T cell (Treg) biology have been associated with human systemic autoimmune diseases, such as systemic lupus erythematosus (SLE). However, the origin of such Treg defects and their significance in the pathogenesis and treatment of SLE are still poorly understood. Methods Peripheral blood mononuclear cells (PBMC) from 61 patients with SLE and 52 healthy donors and in vitro IL-2 stimulated PBMC were characterised by multicolour flow cytometry. Five patients with refractory SLE were treated daily with subcutaneous injections of 1.5 million IU of human IL-2 (aldesleukin) for five consecutive days, and PBMC were analysed by flow cytometry. Results Patients with SLE develop a progressive homeostatic dysbalance between Treg and conventional CD4+ T cells in correlation with disease activity and in parallel display a substantial reduction of CD25 expression on Treg. These Treg defects resemble hallmarks of IL-2 deficiency and lead to a markedly reduced availability of functionally and metabolically active Treg. In vitro experiments revealed that lack of IL-2 production by CD4+ T cells accounts for the loss of CD25 expression in SLE Treg, which could be selectively reversed by stimulation with low doses of IL-2. Accordingly, treatment of patients with SLE with a low-dose IL-2 regimen selectively corrected Treg defects also in vivo and strongly expanded the Treg population. Conclusions Treg defects in patients with SLE are associated with IL-2 deficiency, and can be corrected with low doses of IL-2. The restoration of endogenous mechanisms of immune tolerance by low-dose IL-2 therapy, thus, proposes a selective biological treatment strategy, which directly addresses the pathophysiology in SLE.

Objective To determine the clinical value of six traditional and three IFN-related biomarkers in monitoring disease activity (DA) in SLE. Methods Prospective longitudinal study of IFNα, IFNγ-inducible protein 10 (IP-10) and sialic acid-binding Ig-like lectin 1 (SIGLEC1) vs antibodies against dsDNA (ELISA and Farr radioimmunoassay), dsDNA-complexed nucleosomes (anti-dsDNA-NcX: ELISA), nucleosomes (ANuA: ELISA) and complement C3/C4 for correlation with DA (measured by BILAG 2004 index) in 26 SLE patients (77 visits). Optimal upper and lower longitudinal thresholds for the biomarkers and their accuracies for reflecting clinically relevant changes in DA (flares and remission) were determined by receiver operating characteristic and Youden index analysis. Results Increases in IP-10, SIGLEC1 and ANuA to + 101.6 pg/ml, +5.01 relative mean fluorescence intensity and +16.20 IU/ml above the calculated upper longitudinal threshold significantly reflected lupus flares, with a sensitivity and specificity of 50 and 95% for IP-10, 83 and 90% for SIGLEC1 and 58 and 95% for ANuA. Decreases in anti-dsDNA (ELISA), IFNα and anti-dsDNA (Farr assay) to - 64.7 IU/ml, -16.69 pg/ml and -3.3 IU/ml below lower longitudinal thresholds, respectively, best reflected remission, with sensitivity and specificity of 75 and 95%, 62 and 90%, and 75 and 90%, respectively. Conclusion IP-10, SIGLEC1 and ANuA emerged as advantageous biomarkers for monitoring disease activity. This is the first study in SLE that provides longitudinal biomarker thresholds and test accuracies for SLE flares and remitting disease. In the context of IFN-directed therapies, chemokines and fluorescence-activated cell sorting-based IFN biomarkers for monitoring SLE activity should be further studied.

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).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.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; p0.0001) and SIGLEC-1 (r=0.54; p0.0001) 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; p0.0001) 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.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.

Objective Autoreactive CD4 T cells specific for nuclear peptide antigens play an important role in tolerance breakdown during the course of systemic lupus erythematosus (SLE). However, reliable detection of these cells is limited due to their low frequency in peripheral blood. The authors assess autoreactive CD4 T cells in a representative SLE collective (n=38) by flow cytometry and study the influence of regulatory T cells (Treg) on their antigenic challenge. Methods CD4 T-cell responses were determined according to intracellular CD154 expression induced after 6-h short-term in-vitro stimulation with the SLE-associated autoantigen SmD1(83-119). To clarify the influence of Treg on the activation of autoreactive CD4 T cells, CD25 Treg were depleted by magnetic activated cell sorting before antigen-specific stimulation in selected experiments. Results In the presence of Treg, autoreactive CD4 T-cell responses to SmD1(83-119) were hardly observable. However, Treg removal significantly increased the frequency of detectable SmD1(83-119)-specific CD4 T cells in SLE patients but not in healthy individuals. Consequently, by depleting Treg the percentage of SmD1(83-119)-reactive SLE patients increased from 18.2% to 63.6%. This unmasked autoreactivity of CD4 T cells correlated with the disease activity as determined by the SLE disease activity index (p=0.005*, r=0.779). Conclusions These data highlight the pivotal role of the balance between autoreactive CD4 T cells and CD25 Treg in the dynamic course of human SLE. Analysing CD154 expression in combination with a depletion of CD25 Treg, as shown here, may be of further use in approaching autoantigen-specific CD4 T cells in SLE and other autoimmune diseases.

Objective The high frequency of CD4+ T cells in interstitial infiltrates of patients with lupus nephritis suggests a contribution of these cells to local pathogenesis. The aim of this study was to examine the role of CXCR3 and the chemokine CXCL10 in recruiting these cells into the kidney and to determine whether the infiltrating T cells could be monitored in the urine to provide a reliable biomarker for acute lupus nephritis. Methods The frequencies of CD3+ T cells, CXCR3+ cells, and CXCL10+ cells were determined by immunohistochemical and immunofluorescence analyses of kidney sections from 18 patients with lupus nephritis. The frequency of CXCR3+CD4+ T cells was determined by flow cytometry of peripheral blood and urine from 38 patients with systemic lupus erythematosus (SLE), and the values were compared with disease activity as determined by the Systemic Lupus Erythematosus Disease Activity Index. Results In renal biopsy tissues from patients with lupus nephritis, a mean of 63% of the infiltrating cells expressed CXCR3, approximately 60% of them were T cells, and the CXCR3+ cells colocalized with CXCL10-producing cells. In biopsy tissues from SLE patients with acute nephritis, approximately 50% of the urinary CD4+ T cells were CXCR3+, as compared with 22% in the peripheral blood, and the frequency of urinary CXCR3+CD4+ T cells correlated with disease activity. Moreover, the number of urinary CD4+ T cells reflected nephritis activity, and elevation above 800 CD4+ T cells per 100 ml of urine sharply delineated active from inactive nephritis. Conclusion CXCR3+ T cells are recruited into the inflamed kidneys, are enriched in the urine, and are a valuable marker of nephritis activity in SLE. They also present a potential target for future therapies.

Regulatorischen T-Zellen kommt eine Schlusselrolle bei der Aufrechterhaltung der Immuntoleranz zu und ihr Einsatz konnte eine entscheidende Rolle in unserem therapeutischen Repertoire einnehmen. Die vorliegende Arbeit soll einen Uberblick uber den aktuellen Stand der Forschung uber regulatorische T-Zellen geben. Ein Teil dieser Zellen entsteht im Rahmen der normalen T-Zellreifung im Thymus, andere Subtypen konnen in der Peripherie induziert werden. Regulatorische T-Zellen zeichnen sich durch folgende Besonderheiten aus: Sie proliferieren kaum, hemmen die Aktivierung anderer T-Zellen und sind protektiv gegen Autoimmunerkrankungen. Die zugrundeliegenden Wirkungsmechanismen sind noch nicht vollstandig aufgeklart, wahrscheinlich spielen Zell-Zell-Kontakt-abhangige Mechanismen und Zytokine wie IL-10 und TGFβ eine Rolle. Zur Identifizierung von regulatorischen T-Zellen sind neben CD25 noch andere Oberflachenmarker bekannt, allerdings ist bisher kein Markermolekul bekannt, das ausschlieslich bei regulatorischen T-Zellen nachweisbar ist. Abschliesend wird ein Ausblick uber mogliche therapeutische Anwendung dieser Zellen gegeben.

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.

Objectives: Systemic lupus erythematosus (SLE) shows a strong sex bias, preferentially affecting females, and B cells are thought to play a pivotal role in its pathogenesis. Here, we compared the splenic B-cell compartments, their autoreactivity and activation threshold of female and male NZB/W F1, a murine lupus model reflecting the sex bias observed in patients with SLE. Methods: Autoantibody levels and the amount of autoantibody secreting cells were determined using ELISA and ELISPOT. Flow cytometry and immunofluorescence were applied to analyse the composition of the splenic B-cell pool. Purified follicular (FO) and marginal zone (MZ) B cells were stimulated and the frequency of autoreactive cells was determined. Finally, the proliferative response of FO and MZ B cells upon stimulation was assessed using CFSE dilution and [3H]-Thymidin incorporation. Results: Higher autoantibody titres were detected in female NZB/W F1 mice, which were mainly produced in the spleen. Analysing the composition of the splenic B-cell subsets, no differences were found prior to disease development. Autoreactive dsDNA-specific B cells were mostly found in the MZ compartment, while SmD1(83–119)-reactive cells were more evenly distributed. Equal frequencies of autoreactive B cells were found in female and malemice, and no difference in the response to polyclonal stimuli of the cells of both sexes was detected. Conclusions: No differences in the composition or functionality of splenic B cells were observed that account for the different disease course in both sexes.

Objective Elevated levels of BAFF and APRIL are characteristic of patients with systemic lupus erythematosus (SLE). The reasons for enhanced cytokine production are not well understood. This study was undertaken to identify the cells responsible for the overproduction of these cytokines. Methods BAFF expression was analyzed on peripheral blood mononuclear cells by multiparameter flow cytometry and in tissue samples by immunofluorescence staining. The levels of BAFF and APRIL mRNA were quantified in sorted B cells. In vitro cultures were used to analyze whether B cell survival and differentiation was supported by autocrine BAFF and/or APRIL. Results Aberrant activation of B cells in patients with SLE was associated with a significant up-regulation of BAFF expression in naive, memory, and plasma cells. Furthermore, strong expression of BAFF and APRIL was found in plasma cells from the lymph node, bone marrow, and kidney. The levels of BAFF and APRIL mRNA in CD19+ B cells correlated both with the titer of anti-double stranded DNA antibodies and with the SLE Disease Activity Index. In vitro experiments demonstrated that B cells released functional BAFF/APRIL upon activation. Conclusion Our data show that B cells contribute to the enhanced levels of circulating BAFF and APRIL. The aberrant up-regulation of these cytokines may initiate a vicious circle in which enhanced levels of BAFF and APRIL act in an autocrine manner to reinforce the systemic activation of the humoral immune system.

Interleukin-2 (IL-2) is crucial for the growth and survival of regulatory T cells (Treg), and thus for the control of autoimmunity. In previous studies we have proven the significance of an acquired IL-2 deficiency and related Treg defects in the pathogenesis of systemic lupus erythematosus (SLE). Accordingly, we showed that compensation of IL-2 deficiency by IL-2 therapy corrects associated Treg defects and ameliorates already established disease in lupus-prone mice.1 Proceeding to a clinical translation of IL-2 therapy for SLE, we recently reported a rapid and robust reduction of disease activity in parallel to a remarkable expansion of the Treg population by low-dose IL-2 therapy in one patient with refractory SLE.2 In addition, we showed that Treg defects in SLE patients are associated with IL-2 deficiency, and can be selectively corrected in vitro and in vivo with low doses of IL-2.3 Together, these studies provided the rationales for the clinical implementation an IL-2-based immunotherapy for the treatment of SLE with the aim to restore Treg activity and thus to re-establish endogenous mechanisms of immune tolerance. Here, we present results from the ongoing phase I/IIa clinical trial (PRO-IMMUN) addressing the safety, tolerability, immunological responses and clinical efficacy of a subcutaneous low-dose IL-2 therapy in patients with refractory SLE. References Humrich JY, et al. Homeostatic imbalance of regulatory and effector T cells due to IL-2 deprivation amplifies murine lupus. Proc Natl Acad Sci USA. 2007;107(1):204–209 Humrich JY, et al. Rapid induction of clinical remission by low-dose interleukin-2 in a patient with refractory SLE. Ann Rheum Dis. 2015. doi: 10.1136/annrheumdis-2014-206506 von Spee-Mayer C, et al. Low-dose interleukin-2 selectively corrects regulatory T cell defects in patients with systemic lupus erythematosus. Ann Rheum Dis. Aug 31 2015. doi: 10.1136/annrheumdis-2015-207776. [Epub ahead of print]

Background and objectives Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterised by the development of autoantibodies directed to nuclear components such as SmD1, RNP70, Histone, Ro and La resulting in the loss of tolerance towards these autoantigens. Autoantigen-specific CD4 + T cells are implicated in SLE, but little is known about their frequency in health and disease. To determine frequency of CD4 + T cells specific for SmD1, RNP70, Histone, Ro and La, we generated libraries of polyclonally expanded CD4 + T cells from SLE patients and healthy individuals. In addition, we investigated the accumulation of autoantigen-specific CD4 + T cells in inflamed organ eg, the kidneys of active SLE patients with lupus nephritis. Materials and methods 200.000 CD4 + T cells isolated from the blood and urine of active SLE patients with lupus nephritis (n = 4) or isolated only from the blood of inactive SLE patients (n = 4) and healthy individuals (n = 4) were seeded in multiple micro-cultures containing irradiated feeder cells, PHA and IL-2 for two weeks. Expanded CD4 + T cells were tested for their capacity to proliferate in response to SmD1, RNP70, Histone, Ro and La in the presence of autologous antigen-presenting cells. After 3 days, proliferation was measured after 16-hours pulse with [3H]-thymidine. Results Among 200.000 cells, autoantigen-specific CD4 + T cells are more detectable in active SLE patients in comparison to inactive SLE patients. In healthy individuals, the cells are not or less detectable except in one donor. Autoantigen-specific CD4 + T cells are more enriched in urine than in the peripheral blood of active SLE patients with lupus nephritis. Micro-cultures containing autoantigen-specific CD4 + T cells show a sizeable portion of T cells up-regulated CD154 and IFN-g after 6 h stimulation with autoantigen. Conclusions Our data suggest that SLE-associated autoantigen-specific CD4 + T cells are circulating in the periphery of SLE patients with active disease at higher frequency in comparison to inactive SLE patients and healthy individuals. An accumulation of autoantigen-specific CD4 + T cells was observed in the inflamed kidneys, suggesting their potential role in the local inflammation.

Background 50–80% of SLE patients develop end-stage renal failure (lupus nephritis (LN)) that is one of major causes of morbidity and mortality. Taking renal biopsies is an invasive procedure not free from risk and it is not applicable to monitor LN activity over time. Therefore, the goal of this study was to detect and define cell-based urinary abnormalities and signatures circumventing a critical intervention. We applied mass cytometry to the multiparametric analysis of urine samples of LN patients. Methods Urine and heparin anti-coagulated blood samples were simultaneously collected from 7 LN patients and prepared for mass cytometry analysis. All patients had clinically active SLE and had already started an immunosuppressive therapy. Peripheral blood cells were obtained after erythrocyte lysis. Two panels including 54 surface markers in total were used. Results Mass cytometry allows a comprehensive immunophenotyping of immune cells washed out in urine circumventing problems regarding sample size, autofluorescence-induced artefacts and spectral overlap inherent in conventional flow cytometry. Neutrophils and monocytes/macrophages followed by T cells represent the dominant leukocytes populations in urine samples of SLE patients. The elevated CD8 T cell count was used as biomarker for proliferative LN among SLE patients. Although T cells were below 3% of CD45+ cells, we were able to observe a decreased CD4/CD8 ratio as already described in the literature for LN blood. Additionally, a T cell subpopulation expressing the activation marker CD69 and CD38 was identified in urine but not in blood. Active LN patients show a raised urinary monocyte/macrophage population (CD14+CD36+HLA-DR++). Conclusion First patient data shown indicate that leukocytes detectable in urine of LN patients are promising biosensors reflecting chronic inflammation in the kidneys. Obviously, the LN histopathologic heterogeneity seems to be better reflected by urinary cell populations than by peripheral blood. Therefore, larger patient cohorts and additional epithelial markers will be analysed to identify robust biosignatures that can be used diagnostically for a classification of lupus nephritis.

Objectives The aim of the study was to analyse the cytokine memory of T-cells derived from systemic lupus erythematosus (SLE) patients and healthy donors enriched for autoantigen-specific T-cells by in vitro stimulation with SmD1(83-119), a common autoantigen in SLE. Methods Autoreactive CD3+ T-cells derived from 37 SLE patients and 14 healthy donors were enriched by repetitive ex vivo stimulation of peripheral blood mononuclear cells (PBMCs) with SmD1(83-119). For control, PBMCs were stimulated only with interleukin-2 (IL-2). After two rounds of antigenic stimulation, cultures were stimulated with PMA/ionomycin to probe the cytokine memory by intracellular cytokine staining. Frequencies of cytokine-expressing T-cells were analysed and, in SLE patients, compared with disease activities and autoantibody levels. Results Comparing the cytokine memory in the cultures, SLE patients displayed higher frequencies of tumour necrosis factor-alpha (TNF-alpha)+ T-cells than healthy donors and the frequencies correlated with disease activity. Frequencies of SmD1(83-119)-specific TNF-alpha+ T-cells and of memory T-cells expressing interferon-gamma (IFN-gamma) correlated with serum anti-dsDNA antibody levels. The frequencies of IL-10 expressing SmD1(83-119)-specific T-cells were lower among PBMCs of SLE patients. Relatively higher frequencies of IL-10+ T-cells in SLE patients correlated with low disease activities, and low anti-dsDNA and anti-SmD1(83-119) antibody concentrations in culture supernatants. Conclusions The memory of autoreactive SmD1(83-119)-specific and unspecific stimulated peripheral Th cells for re-expression of cytokines is shifted towards more cells expressing TNF-alpha and less IL-10+ cells, when compared SLE patients with normal donors. This shift towards proinflammatory memory effector Th cells correlates with disease severity and humoral autoimmunity.

The role of T cell-derived cytokine production in lupus is poorly understood. We analysed the cytokine production of CD4(+) T cells in the NZB/W F1 mouse strain, the mouse model probably most closely resembling human systemic lupus erythematosus (SLE), and assessed whether a possible shift in the cytokines expressed is associated with age or disease activity.We used intracellular cytokine staining and flow cytometry to determine the cytokine expression of splenic CD4(+) T cells for interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4) and IL-10. NZB/W F1 mice at different ages spanning 5 to 36 weeks were analysed, healthy Balb/cxNZW F1 (CWF1) mice were used as controls. Serum anti-double-stranded DNA (anti-dsDNA) antibody levels were determined by enzyme-linked immunosorbent assay (ELISA), and proteinuria and plasma creatinine were estimated using commercial test kits.The cytokine profile of CD4(+) T cells was shifted towards T-helper 1 (Th1) cells and the frequencies of Th cells expressing IFN-gamma(+) correlated with age, anti-dsDNA-immunoglobulin G (IgG) titre and proteinuria. An increased percentage of IL-10 producers correlated positively with anti-dsDNA-IgG and proteinuria, and a small gain in IL-4 producers correlated with plasma creatinine. Neither the percentage of IL-10 producers nor IL-4 producers showed a significant correlation with age. There was no significant change observed in the frequency of TNF-alpha T cells. The IFN-gamma/IL-4 ratio demonstrated an increasing shift towards a Th1-type response during disease development that was not present in healthy mouse strains.The association between the frequencies of T cells expressing IFN-gamma and IL-10 and clinical findings suggests a key role for these cells in the pathogenesis of lupus.

Background Local T cell infiltration is considered to play an important role in the pathogenesis of lupus nephritis (LN), one of the major complications of Systemic Lupus Erythematosus (SLE). The renal inflitrating cells can also be found in high numbers in the urine of patients with active LN, however little is known about how these cells are recruited into the inflamed kidney. Objectives Identifying how conventional CD4+ and CD8+ T cells and regulatory T cells (Treg) are recruited into the inflamed kidney in LN. Methods Serum and urine samples of 98 SLE patients were analyzed for 17 chemokines using multiplex assays. Based on the assay’s results a group of 8 corresponding chemokine receptors (CCR1 - 6, CXCR3 and CXCR6) was chosen, whose frequencies on urinary T cells were subsequently determined in 7 patients with acute LN by flowcytometry. Results 10 chemokines* were significantly elevated in the urine of patients with active LN when compared to the control group. The other 7 chemokines° showed no significant differences between the groups. CCR5 and CXCR3 were the most prominent receptors on both urinary CD4+ and CD8+ T cells, although CD4+ T cells also expressed high amounts of CCR4 and CCR6. The chemokine receptor expression on CD4+FoxP3+CD127- Treg differed from conventional CD4+ T cells as well. Treg expressed significantly more CCR4 and significantly less CXCR6. *: CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11, CXCL9, CXCL10 and CXCL16 °: CCL1, CCL17, CCL20, CCL22, CXCL1, CXCL5 and CXCL11 Conclusions CCR5 and CXCR3 are the primary receptors in the mechanism of recruiting all T cells into the inflamed kidney. Key chemokines for T cell attraction are CCL4, CCL5 and CCL8 as well as CXCL9 and CXCL10. However, at least for CD4+ T cells, there are secondary pathways of recruitment involving CCR4 and CCR6. Also, Treg recruitment seems to rely more on CCR4 than that of conventional CD4+ T cells. Disclosure of Interest None Declared

Background Lupus nephritis (LN) is one of the main concerns in the treatment of patients with SLE. However there are no good laboratory markers to non-invasively detect and monitor kidney inflammation in patients with LN. We and others have previously reported that urinary CD4 T cells may serve as a biomarker for acute LN, however these existing studies are limited by their relatively small sample size. Objectives To confirm that urinary CD4 T cells reflect lupus nephritis activity and may serve as a marker to monitor the local inflammation in the kidneys. Methods Urine samples from 118 patients with SLE and 10 healthy controls were analyzed using flowcytometry and correlated with the disease activity (SLEDAI). 24 SLE patients were analyzed at the same time point of receiving a kidney biopsy. Results In patients with renal involvement the amount of urinary CD4 T cells correlated closely with the disease activity (SLEDAI), while patients without renal involvement showed only marginal amounts of urinary T cells even during lupus flares. Healthy controls showed no urinary T cells. All patients with biopsy demonstrated proliferative LN showed highly elevated amounts of urinary CD4 T cells, while some patients with class V nephritis presented normal amounts of urinary T cells. Under treatment for acute LN one patient group quickly normalized the amount of urinary CD4 T cells while others showed a persistence of elevated urinary CD4 T cells counts. The latter patient group had a significantly higher disease activity 6 month after induction of treatment compared to the patients with normalized urinary CD4 T cells, indicating that urinary T cell count reflect treatment response. Conclusions Elevated numbers of urinary CD4 T cells reliably identify SLE patients with proliferative LN. Furthermore the amount of urinary CD4 T cells under treatment seems to reflect treatment response. We consequently propose that urinary CD4 T cells can be used to screen for proliferative LN and to monitor the LN activity under treatment. Disclosure of Interest None Declared

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. Electronic supplementary material The online version of this article (doi:10.1186/s13075-015-0600-y) contains supplementary material, which is available to authorized users.