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). 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 (CD14^lowCD15⁺) 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. 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. 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.

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.

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by venous, arterial, or small‐vessel thrombosis and/or pregnancy‐related morbidity, associated with persistent positivity of antiphospholipid antibodies (aPL). Pregnancy‐related morbidity in APS patients is characterized by unexplained fetal deaths, premature birth of morphologically normal newborns, and/or consecutive pregnancy losses before the 10^thweek of gestation. Beta 2‐glycoprotein 1 (ß2GP1) is the main antigen recognized by aPL and plays an essential role in the pathogenesis of APS. Antibodies against ß2GP1 (aß2GP1) are involved in damage‐generating mechanisms in APS due to their interaction with trophoblasts, decidua, and endothelial cells. aß2GP1 might be used as a prognostic tool for obstetric risk stratification and ß2GP1 could be a target for molecular‐targeted treatment to prevent pregnancy morbidity in APS. This review describes these aspects of aß2GP1, including effects on different cellular targets, its association with the severity of obstetric manifestations and the potential of ß2GP1‐targeted therapies for APS.

To compare immune cell subsets and interferon (IFN) expression in placentas from patients with systemic lupus erythematosus (SLE), primary Sjögren’s disease (pSjD), antiphospholipid syndrome (APS), healthy controls (HC) and of women with adverse pregnancy outcomes (APO) without these systemic rheumatic diseases (SRD). Placenta biopsies from HC, SLE, pSjD, APS, and patients with fetal growth restriction (FGR), spontaneous preterm birth (PTB), or FGR and preeclampsia (FGR/PE) attended between 2008 and 2022 were recovered from the pathology biobank of the University Medical Center Groningen. Clinical characteristics and APO were retrieved from medical records. Immunohistochemistry was performed for Myxovirus resistance protein 1 (MxA), CD3, CD20, CD56, CD68, CD123, and Foxp3. The proportion of positive cells was established using an automated detection classifier, while MxA expression was assessed semi/quantitatively discriminating between maternal (decidua) and fetal (villi) tissue. Finally, placental lesion classification was performed. Our study included placentas from 11 SLE, 4 pSjD, 8 APS, 4 PTB, 8 FGR, 8 FGR/PE patients and 11 HC. A high rate of APO (70%) was identified in SRD patients. Patients with SRD had a higher macrophage (CD68+) count in decidua and villi than HC, but no differences were observed in T (CD3+), B (CD20+), NK (CD56+) and T regulatory (Foxp3+) cell count. No plasmacytoid dendritic cells (CD123+) were identified. Furthermore, patients with these SRD had higher MxA values than HC in villi but not in decidua. SLE, pSjD and APS patients have an increased macrophage count and interferon upregulation in the placenta compared to HC. Therefore, a pro-inflammatory environment might be key inducing placental dysfunction, which may lead to subsequent APO development.

ObjectiveImmunoglobulin G (IgG) autoantibodies in systemic lupus erythematosus (SLE) are considered pathogenic, whereas immunoglobulin M (IgM) autoantibodies may have protective effects. The aim of this study was to identify whether IgG/IgM autoantibody ratios differ between patients with incomplete systemic lupus erythematosus (iSLE), patients with SLE, and healthy controls (HCs), and whether IgG/IgM autoantibody ratios relate to progression from iSLE to SLE.MethodThis prospective cohort study included 34 iSLE patients, 41 SLE patients, and 11 HCs. IgG and IgM anti-dsDNA, anti-Ro52, and anti-Ro60 were measured by fluoro-enzyme immunoassay in serum samples obtained at baseline in all groups and in follow-up samples of up to 5 years for iSLE patients. Correlations between IgG/IgM autoantibody ratios, interferon signature, and clinical parameters were also assessed.ResultsAt baseline, IgG anti-dsDNA, anti-Ro52, anti-Ro60, and IgM anti-dsDNA were elevated in iSLE and SLE patients. IgG/IgM anti-dsDNA and anti-Ro52 ratios were similar between groups, while IgG/IgM anti-Ro60 ratios were significantly elevated in iSLE and SLE patients compared to HCs. IgG/IgM autoantibody ratios were not correlated with interferon signature or clinical parameters. IgG/IgM ratios at baseline were similar and remained relatively stable during a median follow-up of 18 months in non-progressors and six iSLE patients who progressed to SLE.ConclusionIgG anti-dsDNA, anti-Ro52, anti-Ro60, and IgM anti-dsDNA were elevated in iSLE and SLE patients, which was not apparent from the respective IgG/IgM ratios only. IgG/IgM autoantibody ratios remained relatively stable over up to 5 years in iSLE non-progressors and six patients who progressed to SLE.

Endometrial immune profiling as a new tool for preconceptional assessment in patients with systemic autoimmune diseases