Low density granulocytes and neutrophil extracellular trap formation are increased in incomplete systemic lupus erythematosus.

OBJECTIVE: To investigate the proportion of low-density granulocytes (LDGs), circulating plasma neutrophil extracellular traps (NETs), and serum-induced NET formation in patients with incomplete systemic lupus erythematosus (iSLE) and systemic lupus erythematosus (SLE). METHODS: LDGs were measured cross-sectionally in 18 iSLE patients, 11 SLE patients and 14 healthy controls (HCs), whereas circulating NETs and serum-induced NET formation were assessed in 35 iSLE patients, 41 SLE patients and 16 HCs. LDGs (CD14lowCD15+) were measured in PBMCs using flow cytometry and circulating plasma NETs were measured using anti-myeloperoxidase-DNA, anti-citrullinated histone H3 and anti-elastase-DNA complex ELISAs. Serum-induced NET formation was assessed by incubating healthy neutrophils with serum from iSLE patients, SLE patients or HCs and visualizing NETs with fluorescence microscopy. RESULTS: Proportions of LDGs and circulating plasma NETs were similarly elevated in iSLE and SLE patients compared with those in HCs. Furthermore, patients under hydroxychloroquine (HCQ) treatment had lower proportions of LDGs than those without. Serum from iSLE and SLE patients similarly induced NET formation in healthy neutrophils. In iSLE patients, myeloperoxidase-DNA complexes were correlated with proportions of age-associated B-cells, memory B-cells and negatively with naïve B-cells, while we did not find associations between measures of NETs or serum-induced NET formation and interferon score or clinical parameters. CONCLUSION: These results show that neutrophil dysfunction, including higher proportions of LDGs, and increased NET formation, already occur in iSLE, similar to SLE, despite differences in disease manifestations. Thereby, neutrophil dysfunction may contribute to sustained exposure to autoantigens and autoreactivity in early stages of SLE.

Epidermal ZBP1 stabilizes mitochondrial Z-DNA to drive UV-induced IFN signaling in autoimmune photosensitivity.

Photosensitivity is observed in numerous autoimmune diseases and drives poor quality of life and disease flares. Elevated epidermal type I interferon (IFN) production primes for photosensitivity and enhanced inflammation, but the substrates that sustain and amplify this cycle remain undefined. Here, we show that IFN-induced Z-DNA binding protein 1 (ZBP1) stabilizes ultraviolet (UV)B-induced cytosolic Z-DNA derived from oxidized mitochondrial DNA. ZBP1 is significantly upregulated in the epidermis of adult and pediatric patients with autoimmune photosensitivity. Strikingly, lupus keratinocytes accumulate extensive cytosolic Z-DNA after UVB, and transfection of keratinocytes with Z-DNA results in stronger IFN production through cGAS-STING activation compared to B-DNA. ZBP1 knockdown abrogates UV-induced IFN responses, whereas overexpression results in a lupus-like phenotype with spontaneous Z-DNA accumulation and IFN production. Our results highlight Z-DNA and ZBP1 as critical mediators for UVB-induced inflammation and uncover how type I IFNs prime for cutaneous inflammation in photosensitivity.

The effects of hydroxychloroquine and its promising use in refractory obstetric antiphospholipid syndrome.

Hydroxychloroquine (HCQ) is obtained by hydroxylation of chloroquine (CQ) and the first indication was malaria. Nowadays, HCQ is commonly used in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) with favorable results. Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity and persistent positivity of antiphospholipid antibodies. Around 20-30% of pregnant women with APS develop adverse pregnancy outcomes despite conventional treatment with aspirin and heparin, called refractory obstetric APS. Interestingly, HCQ has shown positive effects on top of the standard of care in some refractory obstetric APS patients. HCQ mechanisms of action in APS comprise its ability to bind sialic acid present in cell membranes, its capacity to block the binding of antiphospholipid antibodies to the cell and the induced increase of pH in extracellular and intracellular compartments. However, the precise mechanisms of HCQ in the specific situation of refractory APS still need to be fully clarified. Therefore, this review summarizes the known modulating effects of HCQ and CQ, their side effects and use in APS and different pathologies to understand the benefit effects and the mechanism of action of HCQ in refractory obstetric APS.

Proportions of B-cell subsets are altered in incomplete systemic lupus erythematosus and correlate with interferon score and IgG levels.

OBJECTIVES: Incomplete SLE (iSLE) patients display symptoms typical for SLE but have insufficient criteria to fulfil the diagnosis. Biomarkers are needed to identify iSLE patients that will progress to SLE. IFN type I activation, B-cell-activating factor (BAFF) and B-cell subset distortions play an important role in the pathogenesis of SLE. The aim of this cross-sectional study was to investigate whether B-cell subsets are altered in iSLE patients, and whether these alterations correlate with IFN scores and BAFF levels. METHODS: iSLE patients (n = 34), SLE patients (n = 41) with quiescent disease (SLEDAI ≤4) and healthy controls (n = 22) were included. Proportions of B-cell subsets were measured with flow cytometry, IFN scores with RT-PCR and BAFF levels with ELISA. RESULTS: Proportions of age-associated B-cells were elevated in iSLE patients compared with healthy controls and correlated with IgG levels. In iSLE patients, IFN scores and BAFF levels were significantly increased compared with healthy controls. Also, IFN scores correlated with proportions of switched memory B-cells, plasma cells and IgG levels, and correlated negatively with complement levels in iSLE patients. CONCLUSION: In this cross-sectional study, distortions in B-cell subsets were observed in iSLE patients and were correlated with IFN scores and IgG levels. Since these factors play an important role in the pathogenesis of SLE, iSLE patients with these distortions, high IFN scores, and high levels of IgG and BAFF may be at risk for progression to SLE.