Background: B cells are central in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides (AAV). The efficacy of remission induction and maintenance by B cell depleting therapy strongly underlines the importance of B cells in the disease and the use of rituximab (RTX) has successfully been implemented in the treatment of AAV. However, B cell depletion after application of RTX is markedly prolonged in AAV compared to other autoimmune diseases, suggesting an impairment of the B cell compartment. Objectives: Our study aimed to understand the base of the defect in B cell reconstitution after RTX treatment in AAV, and to dissect B cell function and development in AAV. Methods: We recruited 91 AAV patients and performed deep phenotyping of the peripheral B cell compartment by spectral flow cytometry. In a subgroup of patients, we analyzed the bone marrow using flow- as well as mass cytometry. In vitro modeling assays of B lymphopoiesis have been applied to study dynamic of development of AAV B cell precursors. BAFFR involvement into peripheral B cell survival and maturation have been studied by investigating serum BAFF concentration by ELISA, BAFFR expression of isolated B cells was determined by qPCR and Western Blot, and by in vitro survival assays. Results: AAV patients show B-lymphocytopenia. Low transitional B cell numbers in treatment-naive patients indicate an impaired central B cell development. In RTX-treated AAV patients the median time of B cell depletion, defined as less than 5 cells/µL, was 17 months (IQR 9-36). We studied phenotype and development of bone marrow B cells and found a defect in early B cell development in both treatment-naive and RTX-treated AAV patients. Only in a subgroup of RTX-treated patients, transitional B cells were increased, indicative of beginning or ongoing B cell repopulation. The increased amount of transitional B cells did not lead to replenishment of the later stages of peripheral B cell maturation, suggesting a maturation stop in peripheral B cell reconstitution in these patients. We found low BAFFR expression in AAV peripheral B cells, caused by enhanced shedding of BAFFR, that resulted in a reduced B cell survival in response to BAFF. Conclusion: Our data suggest that prolonged depletion of B cells in AAV patients after RTX therapy indicate a B cell defect that is unmasked by treatment. Impaired central B lymphopoiesis associated with disturbed peripheral B cell maturation because of enhanced BAFFR processing and shedding, resulting in reduced immature B cell survival, contribute to a delayed recovery of the peripheral B cell pool after RTX treatment in AAV. Our data point to a severe defect in B cell maturation and development in patients with AAV that may influence the therapeutic use of B cell depleting agents in this disease. In addition, our results emphasize the need for close immune monitoring after B cell depletion in AAV. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.

Background: The activation of neutrophils via anti-neutrophil cytoplasmic antibodies (ANCA), degranulation and formation of extracellular traps (NETs) are central processes in the pathogenesis of ANCA-associated vasculitis. As a result of increased NETosis, increased cell-free DNA, in particular mitochondrial DNA, was observed in the plasma of these patients (1). In contrast to granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA) is driven by eosinophils and almost 70% of patients are ANCA negative. Objectives: The aim of the study was to investigate circulating cell-free DNA as a potential biomarker in patients with EGPA compared to GPA and MPA patients and healthy controls. Methods: Total DNA was isolated from platelet-free plasma samples from patients with EGPA, GPA or MPA and healthy donors (HD). Copy numbers were quantified by qPCR for mitochondrial (mt) DNA (ATP-6 gene) and nuclear (n) DNA (GAPDH gene). Results: 30 EGPA patients (mean age 56.8 ± 13.3 years, mean BVAS 1.73 ± 5.13, 13.33% ANCA positive (4/30)), 80 GPA patients (mean age 62.4 ± 15.1 years, mean BVAS 1.79 ± 4.86), 21 MPA patients (66.0 ± 9.72 years, mean BVAS 2.14 ± 5.14) and 128 HD (48.4 ± 15.3) were analyzed. Compared to HD, median total cell free DNA was 1.5-fold higher in EGPA (p=0.0291, Mann-Whitney test) and was comparable to values in GPA and MPA patients (Figure 1A). Especially mtDNA levels were significantly increased in EGPA (1.36x108 copies/ml plasma, 95% CI: 6.95x107 to 2.02x108) compared to HD (7.8x106 copies/ml plasma, 95% CI: 6.70x106 to 8.94x106, p<0.0001) (Figure 1C). The amount of circulating mtDNA in EGPA was similar to that in patients with GPA or MPA. The nDNA concentrations in plasma did not differ between EGPA (6.61x106 copies/ml plasma, 95% CI: 4.08x106 to 9.15x106), GPA (8.38x106 copies/ml plasma, 95% CI: 5.1x106 to 11.65x106), MPA (2.28x107 copies/ml plasma, 95% CI: -9.73x106 to 5.53x107) and HD (6.55x106 copies/ml plasma, 95% CI: 2.66x106 to 10.44x106). In a linear regression model, pulmonary involvement, BVAS score and cell-free DNA levels significantly predicted mtDNA levels in EGPA/GPA/MPA patients (p<0.001, respectively p=0.031 and p=0.037). Receiver operating characteristic curve (ROC) analysis showed that a cut-off value of 1.50x107 mtDNA copy numbers differentiated between EGPA and HD with 86.67% sensitivity, 86.72% specificity and an AUC of 0.95 (Figure 2 C). In this cohort, only 4 patients had active EGPA with elevated CRP, eosinophils and BVAS at the time of analysis. MtDNA levels were increased but not significantly higher than in patients with inactive disease. There were no significant differences between ANCA positive (4/30) vs. ANCA negative EGPA patients regarding cell-free DNA levels. Conclusion: The quantification of cell free mtDNA, but not nDNA copy numbers allows a differentiation between healthy donors and patients with EGPA. There were no significant differences to the patients with GPA or MPA, although the latter were much more frequently ANCA positive and were presumably more strongly driven by neutrophils than EGPA. Future studies should include more patients with active disease and follow-up visits. REFERENCES: [1] Giaglis S, et al. Mitochondrial DNA: a novel indicator of active inflammation in ANCA-associated vasculitides. Rheumatology (Oxford). 2023 Aug 1;62(8):2930-2937. doi:10.1093/rheumatology/kead015. PMID: 36645235; PMCID: PMC10393440. [2] Hashimoto T, et al. Increased Circulating Cell-Free DNA in Eosinophilic Granulomatosis With Polyangiitis: Implications for Eosinophil Extracellular Traps and Immunothrombosis. Front Immunol. 2022 Jan 12;12:801897. doi: 10.3389/fimmu.2021.801897. PMID: 35095884; PMCID: PMC8790570. Acknowledgements: NIL. Disclosure of Interests: UW is coinventor of patents owned by Freiburg University; NV is coinventor of patents owned by Freiburg University. Some parts of this work have already been published (1).

Background Axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) may have a profound impact on health-related quality of life (HRQoL) and sleep despite effective treatment. Objectives To assess sleep and HRQoL in SpA and determine associated factors. Methods Monocentric questionnaire-based assessment of HRQoL, function, sleep and depression in 314 SpA patients (n=168 PsA, n=146 axSpA). Results Under effective treatment 138 SpA patients (46.5%) demonstrated abnormal sleep behaviour. 49.3% reported not being able to sleep through the night, with 6.1 % needing sleeping pills. 11.9% indicated feeling unrefreshed most mornings. Abnormal sleep behaviour was associated with female sex (p=0.005), HLAB27 (p=0.034), functional impairment (p=0.001) and depression (p<0.001). Patients reporting unrestful sleep had significantly more depressive symptoms (p<0.001) and highly reduced physical and mental HRQoL (p<0.001). Satisfaction with health was rated significantly lower (p<0.001). Patients with axial involvement (axSpA/axPsA) reported worse sleep quality (p=0.002) and waking too early (p=0.038) despite 73.7% receiving biologics. Sleep quality and early awakening correlated with BASDAI (p<0.001). Smokers had a reduced HRQoL (p=0.018) despite younger age (p=0.008). Female patients had worse sleep quality (p<0.001), needing more time to fall asleep (p=0.022), not being able to sleep through the night (p=0.026) and feeling unrefreshed in the morning (p<0.001). They had a reduced physical (p=0.019) and mental HRQoL (p=0.003), more depressive symptoms (p=0.040) and lower functional capacity (p=0.002). Functional capacity was associated with younger age (p<0.001), sex (p=0.042), smoking (p=0.008), sleep quality (p<0.001) and depression (p<0.001). 66.2% of patients have been assessed longitudinally, before and 3y later during COVID19 pandemic. Physical and mental HRQoL were stable over time. Functional capacity had decreased slightly. Subjective QoL during the COVID19 pandemic was not reduced compared to before. Regarding depressive symptoms, there was a mild but significant improvement over time (p=0.019). Furthermore, we observed an improvement of environmental QoL (p=0.034) during COVID pandemic. Overall subjective QoL as well as satisfaction with health did not change significantly. Patients who had changed therapy (37% of the cohort) still had a reduced physical HRQoL (p=0.022) as well as significantly more depressive symptoms (p=0.010) and perceived their overall QoL as being worse (p=0.016). Conclusion Despite treatment many SpA patients have a reduced HRQoL and impaired sleep quality with significant differences between male and female patients. Impact of COVID19 pandemic was low. Table 1. Patient characteristics Total (n=314 ) Women n=142 (45.2% ) Men n=172 (54.8% ) p-value Age, years, mean (SD) 53.8 (13.9) 53.7 (14.5) 53.8 (13.4) 0.983 BMI, kg/m 2 , mean (SD) 27.3 (6.3) 27.1 (6.5) 27.4 (6.1) 0.706 Smokers, n (%) 68 (23.1) 34 (24.6) 34 (21.7) 0.544 HLA B27, n (%) (n=230) 120 (52.2) 46 (45.1) 54 (54.9) 0.055 CRP, mg/l, mean (SD) 6.14 (11.9) 5.88 (6.0) 6.37 (15.2) 0.721 Significant functional impairment, n (%) 54 (17.5) 29 (20.6) 25 (15.0) 0.198 Therapy, n (%) csDMARD 113 (36.2) 56 (39.7) 57 (33.3) 0.243 bDMARD 211 (67.4) 91 (64.1) 120 (70.2) 0.252 Depressive symptoms, n (%) Mild 109 (37.5) 53 (39.3) 56 (35.9) 0.040 Moderate/severe 48 (16.5) 27 (20.0) 21 (13.5) WHO-QOL mean (SD) Physical 60.2 (19.4) 57.4 (19.7) 62.6 (19.0) 0.019 Mental 67.7 (17.2) 64.5 (17.8) 70.3 (16.2) 0.003 Social 67.8 (20.0) 67.4 (19.6) 68.2 (20.3) 0.703 Environmental 77.3 (13.3) 76.6 (13.6) 78.0 (13.1) 0.363 Sleep, n (%) Abnormal sleep behaviour 138 (46.5) 76 (55.1) 62 (39.0) 0.006 Inability to sleep through the night 145 (49.4) 76 (55.1) 69 (44.2) 0.024 Waking too early 89 (30.4) 43 (31.4) 46 (29.5) 0.459 Need for sleeping pills 18 (6.1) 11 (8.0) 7 (4.4) 0.133 Unrefreshing sleep most or all nights 35 (11.9) 24 (17.5) 11 (7.0) <0.001 Figure 1. Female SpA patients have increased depressive symptoms and a reduced HRQoL. Disclosure of Interests Natalie Frede Grant/research support from: Novartis study grant, Eva Rieger: None declared, Raquel Lorenzetti Grant/research support from: Novartis study grant, Ana Venhoff: None declared, Carolin Hentze: None declared, Ilona Jandova: None declared, Cornelia Glaser: None declared, Jens Thiel Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB, Consultant of: Novartis, AbbVie, Pfizer, BMS, UCB, Grant/research support from: BMS, Novartis study grants, Reinhard Voll Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB, Consultant of: Novartis, AbbVie, Pfizer, BMS, UCB, Lilly, Grant/research support from: Novartis study grant, Nils Venhoff Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB, Consultant of: Novartis, AbbVie, Grant/research support from: Novartis study grant

Background Respiratory tract infections (RTIs) are the most common infections in patients with rheumatic diseases under immunosuppressive treatment. RTIs may cause significant morbidity with reduced quality of life (QOL), increased healthcare costs and may lead to interruption of DMARD therapy. However, to date only limited data on infection risk in spondyloarthritis (SpA) patients are available. Objectives To assess the occurrence of respiratory tract infections in a real-world SpA cohort and determine associated factors. Methods Questionnaire-based screening and retrospective medical chart analysis of a monocentric cohort of 314 SpA patients comprising 168 psoriatic arthritis (PsA) and 146 axial spondyloarthritis (axSpA) patients. Results Out of 314 SpA patients, 89% had a history of upper respiratory tract infections (URTI) and 31.1% of lower respiratory tract infections (LRTI) within the last two years (Table 1). In a linear regression model LRTIs were associated with glucocorticoid (GC) therapy (p=0.015), CRP level (p=0.018), previous history of severe respiratory infections (p=0.007) as well as absence of HLA B27 (p=0.024). In general, patients with LRTIs were significantly older (p=0.007), had increased functional impairment (p<0.001), a reduced health-related QOL (p<0.001), poorer sleep quality (p=0.001) and more depression (p=0.001). 46% of patients had required antibiotics for RTIs within the last two years. Antibiotic therapy was associated with smoking (p=0.006), biologic therapy (p=0.005) and poor sleep quality (p=0.005). Smoking was associated with LRTI (p=0.009), but not URTI. Female patients reported a significantly higher frequency of LRTI (p=0.003), sinusitis (p=0.001), pharyngitis/laryngitis (p=0.009) and had received more courses of antibiotics than male patients (p=0.032). Table 1. Patient characteristics and infections axSpA (n=146 ) PsA (n=168 ) Total (n=314 ) Age, years, mean (SD) 49.6 (14.2) 57.4 (12.4) 53.8 (13.9) Male / Female, % 56.8 / 43.2 53.0 / 47.0 54.8 / 45.2 BMI, kg/m 2 , mean (SD) 27.1 (7.2) 27.4 (5.4) 27.3 (6.2) Smokers, n (%) 41 (31.8) 27 (16.3) 68 (23.1) HLA B27, n (%) (n=230) 97 (71.9) 23 (24) 120 (52.2) Therapy:n (%) csDMARD 29 (19.6) 84 (50.6) 113 (36.2) bDMARD 109 (75.2) 102 (60.7) 211 (67.4) Glucocorticoids 14 (9.9) 15 (8.9) 29 (9.4) Hypogammaglobulinemia (IgG<7g/l), n (%) 5 (3.5) 6 (3.6) 11 (3.6) Polyclonal IgA (>4g/l) elevation, n (%) 15 (10.9) 29 (17.8) 44 (14.7) URTI: n (%) 114 (88.4) 148 (90.2) 262 (89.4) Rhinitis, % 87.1 87.5 87.3 Laryngitis/pharyngitis, % 37 36.9 36.9 Sinusitis, % 40.5 30.2 34.7 Otitis media, % 14.3 6.8 10.1 LRTI: n (%) 39 (30.5) 52 (32.1) 91 (31.1) Bronchitis, % 28.0 30.6 29.6 Pneumonia, % 3.9 3.1 3.4 Pleuritis, % 2.4 1.2 1.7 There were no significant differences between PsA and axSpA regarding frequency of URTI or LRTI, though PsA patients had tendentially more overall RTIs. Biological therapy did not lead to a significantly increased occurrence of infections, but was associated with increased antibiotic therapy (p=0.039). Patients with a history of pneumonia had received anti-IL17 therapy more frequently (p=0.002), while there was no significant association with anti-TNF therapy (p=0.156). Patients on GC had a relative risk for LRTIs of 2.04. Hypogammaglobulinemia was rare in SpA patients (3.6%) despite continuous immunosuppressive treatment, occurred with equal frequency in axSpa and PsA patients and was associated with pneumonia (p=0.007) and increased antibiotic use (p=0.016). Polyclonal IgA elevation was observed in 14.7% of patients (mean 4.98g/l) and was associated with fewer episodes of rhinitis (p=0.027), whereas LRTIs and antibiotic use did not differ significantly. Conclusion This study quantifies the incidence and effects of RTIs in a real-world SpA cohort. While infections constitute significant adverse events of biologicals, and URTI were common, severe respiratory tract infections were rare. Differences in infection risk between SpA and PsA need to be studied more closely. Disclosure of Interests Natalie Frede Grant/research support from: Novartis study grant, Eva Rieger: None declared, Raquel Lorenzetti Grant/research support from: Novartis study grant, Ana Venhoff: None declared, Anna-Maria Kanne: None declared, Marcus von Deimling: None declared, Nora Bartholomä: None declared, Jens Thiel Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB, Consultant of: Novartis, AbbVie, Pfizer, BMS, UCB, Grant/research support from: BMS, Novartis study grants, Reinhard Voll Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB, Consultant of: Novartis, AbbVie, Pfizer, BMS, UCB, Lilly, Grant/research support from: Novartis study grant , Nils Venhoff Speakers bureau: Novartis, AbbVie, Pfizer, BMS, UCB , Consultant of: Novartis, AbbVie, Grant/research support from: Novartis study grant

Background: JAK inhibitors have been successfully introduced in the treatment of rheumatoid arthritis (RA) and psoriatic arthritis and are in clinical trials for numerous other autoimmune diseases. JAK inhibition effectively reduces cytokine-mediated activation and survival of pathology-driving immune cells by targeting signaling downstream of cytokine receptors. The outcome of such immunomodulation hence will largely depend on the intrinsic expression of the four different JAKs, the cytokine environment and the targeted cell type. Comparative studies investigating the effect on B cells are lacking. In light of the use of JAK inhibitor treatment in autoantibody mediated diseases, the study of the B cell compartment represents a milestone to assess their potential. Objectives: We thus aimed to study the B cell compartment as well as B cell function under JAK inhibition in RA patients and to compare the specific effect the JAK inhibitors tofacitinib (pan-JAK), baricitinib (JAK1/2), ruxolitinib (JAK1/2), upadacitinib and filgotinib (selective JAK1) on in vitro B cell activation, differentiation, proliferation, and class switch. Methods: B cell subpopulations in RA patients treated with baricitinib or tofacitinib was assessed by flow cytometric analysis of peripheral blood mononuclear cells. For in vitro studies, magnetically isolated total B cells from healthy donors were stimulated T-cell -independently with CpG and treated with scalar doses of the JAK inhibitors tofacitinib, baricitinib, ruxolitinib, upadacitinib and filgotinib. Flow cytometric analysis was performed on days 0, 3 and 6. Cytokine secretion was measured by Cytokine Multiplex Assay. Results: B cell phenotyping of RA patients treated with JAK inhibitors baricitinib or tofacitinib showed an increase in marginal zone (MZ) B cells. To investigate this further, we turned to an in vitro model of T-cell-independent B cell activation with CpG via TLR9, known to support MZ B cell expansion. Here, JAK1/2 and selective JAK1 inhibitor treatment led to a dose-dependent decrease of total B cell numbers. When assessing B cell-subpopulations, we observed an altered B cell differentiation with a significant increase in MZ-like B cells under JAK inhibition, which led to a subsequent increase in plasmablast differentiation in the first days. This effect was more pronounced upon pan-JAK inhibitor treatment than JAK1 or JAK1/2 inhibition, indicating that broader JAK inhibition is associated with a stronger effect (tofa > ruxo > bari > upa > filgo). Notably, we further detected a significant dose-dependent reduction of switched memory formation, strongest with JAK1/2 inhibition (upa > ruxo > bari > tofa > filgo). Consistent with this finding, we observed decreased AID expression under JAK inhibition. Concomitantly, induction of STAT3 expression and STAT3 phosphorylation were reduced under JAK inhibition, suggesting that downstream signalling was abrogated. To assess the role of autocrine signaling in this system, we measured cytokine secretion upon JAK inhibition and found that JAK2 inhibition led to reduced IL10 secretion. This in turn resulted in an increase of inflammatory cytokines such as IL6, TNF, highlighting the importance of B cell as cytokine-secreting cell type. Conclusion: In a T-independent in vitro B cell model JAK inhibition led to a reduced total B cell number as well as reduced switched memory development, whereas MZ-like B cells were increased. Especially JAK2 inhibition strongly impaired switched memory formation. JAK inhibition does not only impact cytokine signalling but also leads to changes in cytokine secretion dynamics and amounts, potentially impacting other cell types. In conclusion, JAK inhibition has a major effect on B cell activation and maturation, with differential outcomes between JAK inhibitors hinting towards distinct and unique effects on B cell homeostasis. Disclosure of Interests: None declared

Background: Axial spondyloarthritis (AxSpA) may lead to significant structural damage resulting in marked impairment and disability. Historically, AxSpA has been thought to have a distinct male predominance regarding both, occurrence but also disease severity. However, it has recently been shown in international cohorts that women with AxSpA may have in fact an increased disease burden and worse outcome than their male counterparts. Objectives: The aim of this project was to analyse functional capacity in a German cohort of AxSpA patients and identify associated factors by comparing demographic data, clinical characteristics, disease activity and treatments. Methods: Analysis of a German University Hospital outpatient clinic cohort of 150 AxSpA patients. Questionnaire-based screening tools were used to assess disease activity, functional impairment and quality of life (BASDAI, FFbH, WHOQOL-BREF). Female and male patients were compared by independent samples two-tailed T tests for continuous variables as well as chi-squared test for categorical variables. Results: A German cohort of 150 AxSpA patients with 89 male and 61 female patients (mean age 49.3 years for males, 48.5 for females, p=0.77) was analyzed for functional capacity. Female patients had a significantly higher functional impairment in everyday life compared to males (p=0.013). After adjusting for age, linear regression showed female sex still to be significantly associated with functional impairment. Female patients rated their satisfaction with health as well as their physical and mental health-related quality of life significantly lower than male patients (p=0.015, respectively p=0.003 and p=0.002). There were no significant differences in disease duration, diagnostic delay or family history between male and female patients (p=0.731, p=0.971 and p=0.776). Women had a slightly higher disease activity (BASDAI 4.08 vs. 3.36), although just not statistically significant in our cohort (p=0.056). Female patients had more peripheral joint involvement (52.5% vs. 34.8%, p=0.032), as well as more enthesitis (31.1% vs. 16.9%, p=0.04), whereas there were no differences concerning eye involvement (p=0.51). Female patients were less likely to be HLA B27 positive (65.6 vs. 80.7%, p=0.04). and were less likely to be on anti-TNF treatment (p=0.032, respectively p=0.042). Conclusion: Also in our cohort female patients had a higher burden of disease as well as a worse patient reported outcome with worse quality of life and more self-reported functional impairment in everyday life. These data underline the importance of raising awareness for sex differences in disease presentation and suggest that female patients might require different treatment to achieve improved outcomes. Disclosure of Interests: None declared

Background Rheumatoid arthritis is an immune-mediated disease, in which immune cell activation leads to destructive inflammation of the joints. In this context the treatment with JAK inhibitor tofacitinib has been proven to be effective. In mice treatment with tofacitinib resulted in reduced specific antibody responses, failure to generate germinal centres, and partial block of B cell development in the bone marrow. Conversely in vivo treatment of psoriasis arthritis patients as well as of rheumatioid arthritis patients with tofacitinib results in an increase of relative and absolute numbers of B cells in the first 4–8 weeks from beginning of treatment. It is known that mouse early B cell development is strongly dependent on IL-7 signalling, while this is not essential in humans. Nevertheless other cytokines are important in determining the fate and development of B lymphocytes. Hence, the outcome of JAK inhibition in early B cell development remains to be studied Objectives To assess the impact of JAK inhibition on early B cell development in vitro Methods We used a in vitro model in which CD34+ cells isolated from cord blood are cultivated subsequently in SCF, Flt3-L and IL-6, then SCF, Flt3-L and IL-7 and finally in cytokine-free medium(.1 The culture reproduces all stages of development from common lymphocytes progenitors to immature B cells. Results With the addition of tofacitinib to the in vitro culture we observed an increase in the absolute numbers of lymphoid precursors developing in vitro especially at week 5 and 6 of culture. Specifically, JAK inhibition led to an increase of pre-B and immature B cells by week 5 and 6. These data are in contrast with the early B cell development block observed in the tofacitinib treated mouse, but are in line with the rapid increase of B cells in peripheral blood after 4–8 weeks of tofacitinib treatment in patients. Analysis of induction of fate determining genes (EBF, E2A, PAX-5) showed an earlier and stronger induction of fate determining genes. Conclusions Our data indicate that JAK inhibition may promote early B cell development by enhancing the commitment of lymphoid precursors to the B cell compartment, contributing to a temporary increase in relative and absolute numbers of B cell in peripheral blood of treated patients. These data contribute to our understanding of human B cell development, prompt us to further analyse the quality of B cell output from the bone marrow in JAK inhibited patients, and may provide cues to understand the outcome of JAK inhibition treatment in rheumatic diseases. Reference [1] Kraus H, et al. A feeder-free differentiation system identifies autonomously proliferating B cell precursors in human bone marrow. J Immunol. 2014Feb 1;192(3):1044–54. Disclosure of Interest None declared

BACKGROUND:Cytotoxic T lymphocyte antigen-4 (CTLA-4) limits T-cell activation and is expressed on T-regulatory cells. Human CTLA-4 deficiency results in severe immune dysregulation. Abatacept (CTLA-4 Ig) is approved for the treatment of rheumatoid arthritis (RA) and its mechanism of action is attributed to effects on T-cells. It is known that CTLA-4 modulates the expression of its ligands CD80 and CD86 on antigen presenting cells (APC) by transendocytosis. As B-cells express CD80/CD86 and function as APC, we hypothesize that B-cells are a direct target of abatacept.OBJECTIVES:To investigate direct effects of abatacept on human B-lymphocytes in vitro and in RA patients.METHODS:The effect of abatacept on healthy donor B-cells' phenotype, activation and CD80/CD86 expression was studied in vitro. Nine abatacept-treated RA patients were studied. Seven of these were followed up to 24 months, and two up to 12 months only and treatment response, immunoglobulins, ACPA, RF concentrations, B-cell phenotype and ACPA-specific switched memory B-cell frequency were assessed.RESULTS:B-cell development was unaffected by abatacept. Abatacept treatment resulted in a dose-dependent decrease of CD80/CD86 expression on B-cells in vitro, which was due to dynamin-dependent internalization. RA patients treated with abatacept showed a progressive decrease in plasmablasts and serum IgG. While ACPA-titers only moderately declined, the frequency of ACPA-specific switched memory B-cells significantly decreased.CONCLUSIONS:Abatacept directly targets B-cells by reducing CD80/CD86 expression. Impairment of antigen presentation and T-cell activation may result in altered B-cell selection, providing a new therapeutic mechanism and a base for abatacept use in B-cell mediated autoimmunity.

BackgroundPsoriatic arthritis (PsA) is an inflammatory rheumatic disease affecting approximately 30% of psoriasis (PsO) patients. Despite increased awareness there is still a considerable delay in diagnosis. Untreated PsA may lead to irreversible joint destruction associated with a high rate of disability and depression. A timely diagnosis and initiation of treatment are therefore essential.ObjectivesIn order to minimise diagnostic delay and improve patient care, we have implemented a questionnaire-based screening procedure in the dermatology outpatient clinic to identify patients with suspected PsA.MethodsA questionnaire-based screening (PEST, FFbH, WHOQOL-BREF, Phq9, GHQ-12) was used to assess PsO patients for PsA, depression, comorbidities, and quality of life (QOL).ResultsSo far we have assessed 150 PsO patients. 79% reported joint affection with a mean number of 4.58 involved joint regions, predominantly at the lower extremities. 34% described axial involvement. 42% had a score of ≥3 in the PEST tool, being suspicious for PsA. 4% had a clinically relevant functional impairment in daily life assessed by FFbH questionnaire (score <60%). In WHOQOL-BREF PsO patients scored lower on the physical health as well as the psychological wellbeing scale when compared to reference values for healthy controls, while results in the social relationship and environment domains were comparable. When comparing patients with suspected PsA to PsO without arthritis the former group reached significantly lower scores in the physical health domain (p=0.0001), in the psychological wellbeing (p=0.0434), and environment domains (p=0.0384), especially regarding items assessing body image/appearance and negative feelings for psychological wellbeing as well as physical security and mobility/transport in the environment domain. For the social domain there were no differences. In the Phq9 questionnaire patients reached a mean of 6.5 points equalling mild depressive symptoms. 16% of PsO patients had moderate depressive symptoms, while 9% had severe depressive symptoms. In patients with suspected PsA 44% had moderate (26%) or severe (18%) depression compared to 7% and 2% respectively in PsO patients without arthritis.ConclusionsScreening questionnaires are valuable tools for dermatologists as well as general practitioners and help to identify PsO patients with musculoskeletal involvement pointing towards psoriatic arthritis. Thus, screening questionnaires can add to ensure timely referral of patients with inflammatory joint involvement and depression to the corresponding specialists and help to avoid a delay of treatment. Our data confirm an association of psoriasis, depressive symptoms and reduced quality of life, which was even stronger in patients with psoriatic arthritis.Disclosure of InterestNone declared