Developmental partitioning of SYK and ZAP70 prevents autoimmunity and cancer.

Even though SYK and ZAP70 kinases share high sequence homology and serve analogous functions, their expression in B and T cells is strictly segregated throughout evolution. Here, we identified aberrant ZAP70 expression as a common feature in a broad range of B cell malignancies. We validated SYK as the kinase that sets the thresholds for negative selection of autoreactive and premalignant clones. When aberrantly expressed in B cells, ZAP70 competes with SYK at the BCR signalosome and redirects SYK from negative selection to tonic PI3K signaling, thereby promoting B cell survival. In genetic mouse models for B-ALL and B-CLL, conditional expression of Zap70 accelerated disease onset, while genetic deletion impaired malignant transformation. Inducible activation of Zap70 during B cell development compromised negative selection of autoreactive B cells, resulting in pervasive autoantibody production. Strict segregation of the two kinases is critical for normal B cell selection and represents a central safeguard against the development of autoimmune disease and B cell malignancies.

mTOR Activation Underlies Enhanced B Cell Proliferation and Autoimmunity in PrkcdG510S/G510S Mice.

Autosomal recessive PRKCD deficiency has previously been associated with the development of systemic lupus erythematosus in human patients, but the mechanisms underlying autoimmunity remain poorly understood. We introduced the Prkcd G510S mutation that we previously associated to a Mendelian cause of systemic lupus erythematosus in the mouse genome, using CRISPR-Cas9 gene editing. PrkcdG510S/G510S mice recapitulated the human phenotype and had reduced lifespan. We demonstrate that this phenotype is linked to a B cell-autonomous role of Prkcd. A detailed analysis of B cell activation in PrkcdG510S/G510S mice shows an upregulation of the PI3K/mTOR pathway after the engagement of the BCR in these cells, leading to lymphoproliferation. Treatment of mice with rapamycin, an mTORC1 inhibitor, significantly improves autoimmune symptoms, demonstrating in vivo the deleterious effect of mTOR pathway activation in PrkcdG510S/G510S mice. Additional defects in PrkcdG510S/G510S mice include a decrease in peripheral mature NK cells that might contribute to the known susceptibility to viral infections of patients with PRKCD mutations.

Loss of function of XBP1 splicing activity of IRE1α favors B cell tolerance breakdown.

Anti-nuclear antibodies are the hallmark of autoimmune diseases such as systemic lupus erythematosus (SLE) and scleroderma. However, the molecular mechanisms of B cell tolerance breakdown in these pathological contexts are poorly known. The study of rare familial forms of autoimmune diseases could therefore help to better describe common biological mechanisms leading to B cell tolerance breakdown. By Whole-Exome Sequencing, we identified a new heterozygous mutation (p.R594C) in ERN1 gene, encoding IRE1α (Inositol-Requiring Enzyme 1α), in a multiplex family with several members presenting autoantibody-mediated autoimmunity. Using human cell lines and a knock-in (KI) transgenic mouse model, we showed that this mutation led to a profound defect of IRE1α ribonuclease activity on X-Box Binding Protein 1 (XBP1) splicing. The KI mice developed a broad panel of autoantibodies, however in a subclinical manner. These results suggest that a decrease of spliced form of XBP1 (XBP1s) production could contribute to B cell tolerance breakdown and give new insights into the function of IRE1α which are important to consider for the development of IRE1α targeting strategies.

Normal B cells express ZAP70 in chronic lymphocytic leukemia: A link between autoimmunity and lymphoproliferation?

ZAP70 has a prognostic value in chronic lymphocytic leukemia (CLL), through altered B-cell receptor signaling, which is important in CLL pathogenesis. A good correlation between ZAP70 expression in CLL cells and the occurrence of autoimmune phenomena has been reported. Yet, the great majority of CLL-associated autoimmune cytopenia is due to polyclonal immunoglobulin (Ig) G synthesized by nonmalignant B cells, and this phenomenon is poorly understood. Here, we show, using flow cytometry, that a substantial percentage of CD5- nonmalignant B cells from CLL patients expresses ZAP70 compared with CD5- B cells from healthy subjects. This ZAP70 expression in normal B cells from CLL patients was also evidenced by the detection of ZAP70 mRNA at single-cell level with polyclonal Ig heavy- and light-chain gene transcripts. ZAP70+ normal B cells belong to various B-cell subsets and their presence in the naïve B-cell subset suggests that ZAP70 expression may occur during early B-cell development in CLL patients and potentially before malignant transformation. The presence of ZAP70+ normal B cells is associated with autoimmune cytopenia in CLL patients in our cohort of patients, and recombinant antibodies produced from these ZAP70+ nonmalignant B cells were frequently autoreactive including anti-platelet reactivity. These results provide a better understanding of the implication of ZAP70 in CLL leukemogenesis and the mechanisms of autoimmune complications of CLL.

Severe combined immunodeficiency in stimulator of interferon genes (STING) V154M/wild-type mice.

BACKGROUND: Autosomal dominant gain-of-function mutations in human stimulator of interferon genes (STING) lead to a severe autoinflammatory disease called STING-associated vasculopathy with onset in infancy that is associated with enhanced expression of interferon-stimulated gene transcripts. OBJECTIVE: The goal of this study was to analyze the phenotype of a new mouse model of STING hyperactivation and the role of type I interferons in this system. METHODS: We generated a knock-in model carrying an amino acid substitution (V154M) in mouse STING, corresponding to a recurrent mutation seen in human patients with STING-associated vasculopathy with onset in infancy. Hematopoietic development and tissue histology were analyzed. Lymphocyte activation and proliferation were assessed in vitro. STING V154M/wild-type (WT) mice were crossed to IFN-α/ß receptor (IFNAR) knockout mice to evaluate the type I interferon dependence of the mutant Sting phenotype recorded. RESULTS: In STING V154M/WT mice we detected variable expression of inflammatory infiltrates in the lungs and kidneys. These mice showed a marked decrease in survival and developed a severe combined immunodeficiency disease (SCID) affecting B, T, and natural killer cells, with an almost complete lack of antibodies and a significant expansion of monocytes and granulocytes. The blockade in B- and T-cell development was present from early immature stages in bone marrow and thymus. In addition, in vitro experiments revealed an intrinsic proliferative defect of mature T cells. Although the V154M/WT mutant demonstrated increased expression of interferon-stimulated genes, the SCID phenotype was not reversed in STING V154M/WT IFNAR knockout mice. However, the antiproliferative defect in T cells was rescued partially by IFNAR deficiency. CONCLUSIONS: STING gain-of-function mice developed an interferon-independent SCID phenotype with a T-cell, B-cell, and natural killer cell developmental defect and hypogammaglobulinemia that is associated with signs of inflammation in lungs and kidneys. Only the intrinsic proliferative defect of T cells was partially interferon dependent.

Transitional B cells in quiescent SLE: An early checkpoint imprinted by IFN.

Systemic lupus (SLE) is characterized by a break of B cell tolerance that plays a central role in disease pathophysiology. An early checkpoint defect occurs at the transitional stage leading to the survival of autoreactive B cells and consequently the production of pathogenic autoantibodies. The main purpose of our work was to determine whether transitional B cells, as the most immature naïve B cell subset upstream of pathogenic B cells, display specific features compared to healthy non SLE subjects. Through extensive analysis of transitional B cells from untreated or low treated, mostly Caucasian, SLE patients, we demonstrated that transitional (T1 and T2) B cell frequencies were increased in SLE and positively correlated with disease activity. SLE transitional B cells displayed defects in two closely inter-related molecules (i.e. TLR9 defective responses and CD19 downregulation). RNA sequencing of sorted transitional B cells from untreated patients revealed a predominant overexpression of interferon stimulated genes (ISGs) even out of flares. In addition, early transitional B cells from the bone marrow displayed the highest interferon score, reflecting a B cell interferon burden of central origin. Hence, the IFN signature in transitional B cells is not confined to African American SLE patients and exists in quiescent disease since the medullary stage. These results suggest that in SLE these 3 factors (i.e. IFN imprintment, CD19 downregulation and TLR9 responses impairment) could take part at the early transitional B cell stage in B cell tolerance by-pass, ultimately leading in periphery to the expansion of autoantibodies-secreting cells.

Neutropenia in Patients with Common Variable Immunodeficiency: a Rare Event Associated with Severe Outcome.

BACKGROUND: Common variable immunodeficiency (CVID) is characterized by infections and hypogammaglobulinemia. Neutropenia is rare during CVID. METHODS: The French DEFI study enrolled patients with primary hypogammaglobulinemia. Patients with CVID and neutropenia were retrospectively analyzed. RESULTS: Among 473 patients with CVID, 16 patients displayed neutropenia (lowest count [0-1400]*106/L). Sex ratio (M/F) was 10/6. Five patients died during the follow-up (11 years) with an increased percentage of deaths compared to the whole DEFI group (31.3 vs 3.4%, P < 0.05). Neutropenia was diagnosed for 10 patients before 22 years old. The most frequent symptoms, except infections, were autoimmune cytopenia, i.e., thrombopenia or anemia (11/16). Ten patients were affected with lymphoproliferative diseases. Two patients were in the infection only group and the others belonged to one or several other CVID groups. The median level of IgG was 2.6 g/L [0.35-4.4]. Most patients presented increased numbers of CD21low CD38low B cell, as already described in CVID autoimmune cytopenia group. Neutropenia was considered autoimmune in 11 cases. NGS for 52 genes of interest was performed on 8 patients. No deleterious mutations were found in LRBA, CTLA4, and PIK3. More than one potentially damaging variant in other genes associated with CVID were present in most patients arguing for a multigene process. CONCLUSION: Neutropenia is generally associated with another cytopenia and presumably of autoimmune origin during CVID. In the DEFI study, neutropenia is coupled with more severe clinical outcomes. It appears as an "alarm bell" considering patients' presentation and the high rate of deaths. Whole exome sequencing diagnosis should improve management.

Chronic bacterial infection activates autoreactive B cells and induces isotype switching and autoantigen-driven mutations.

The links between infections and the development of B-cell-mediated autoimmune diseases are still unclear. In particular, it has been suggested that infection-induced stimulation of innate immune sensors can engage low affinity autoreactive B lymphocytes to mature and produce mutated IgG pathogenic autoantibodies. To test this hypothesis, we established a new knock-in mouse model in which autoreactive B cells could be committed to an affinity maturation process. We show that a chronic bacterial infection allows the activation of such B cells and the production of nonmutated IgM autoantibodies. Moreover, in the constitutive presence of their soluble antigen, some autoreactive clones are able to acquire a germinal center phenotype, to induce Aicda gene expression and to introduce somatic mutations in the IgG heavy chain variable region on amino acids forming direct contacts with the autoantigen. Paradoxically, only lower affinity variants are detected, which strongly suggests that higher affinity autoantibodies secreting B cells are counterselected. For the first time, we demonstrate in vivo that a noncross-reactive infectious agent can activate and induce autoreactive B cells to isotype switching and autoantigen-driven mutations, but on a nonautoimmune background, tolerance mechanisms prevent the formation of consequently dangerous autoimmunity.

Immunological phenotype of the murine Lrba knockout.

Biallelic mutations in the human lipopolysaccharide responsive beige-like anchor (LRBA) gene lead to a primary immunodeficiency known as LRBA deficiency, characterized by a broad range of clinical manifestations including autoimmunity, organomegaly, hypogammaglobulinemia and recurrent infections. Considering the phenotypic heterogeneity in patients and the severity of the disease, our aim was to assess the role of LRBA in immune cells and to understand the underlying pathomechanisms through the study of a Lrba knockout (Lrba-/-) mouse model. LRBA-deficient mice did not show severe clinical or immunological signs of disease, either at steady state under specific-pathogen-free conditions, after vaccination with T-dependent and T-independent antigens, or in the context of acute infections with lymphocytic choriomeningitis virus (LCMV) or Salmonella Typhimurium. Although Lrba-/- mice were able to produce normal serum immunoglobulin M (IgM) and IgG and to mount a specific immune response after immunization, they showed elevated serum and secretory basal IgA levels. LRBA was dispensable for B- and T-cell development, as well as for in vitro B-cell proliferation, survival, isotype switching and plasmablast differentiation. Interestingly, Lrba-/- mice displayed decreased cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) expression by regulatory T cells and activated conventional CD4+ and CD8+ T lymphocytes, reduced frequency of peritoneal B-1a cells along with diminished interleukin-10 production and increased percentages of T follicular helper cells in Peyer's patches, but without developing overt signs of autoimmunity. Our findings expand the role of LRBA in immune regulatory mechanisms previously reported in patients, and suggest a novel role in IgA production that is crucial for the protection of mucosal surfaces and gut-associated immune tolerance.

Carabin protects against cardiac hypertrophy by blocking calcineurin, Ras, and Ca2+/calmodulin-dependent protein kinase II signaling.

BACKGROUND: Cardiac hypertrophy is an early hallmark during the clinical course of heart failure and is regulated by various signaling pathways. However, the molecular mechanisms that negatively regulate these signal transduction pathways remain poorly understood. METHODS AND RESULTS: Here, we characterized Carabin, a protein expressed in cardiomyocytes that was downregulated in cardiac hypertrophy and human heart failure. Four weeks after transverse aortic constriction, Carabin-deficient (Carabin(-/-)) mice developed exaggerated cardiac hypertrophy and displayed a strong decrease in fractional shortening (14.6±1.6% versus 27.6±1.4% in wild type plus transverse aortic constriction mice; P<0.0001). Conversely, compensation of Carabin loss through a cardiotropic adeno-associated viral vector encoding Carabin prevented transverse aortic constriction-induced cardiac hypertrophy with preserved fractional shortening (39.9±1.2% versus 25.9±2.6% in control plus transverse aortic constriction mice; P<0.0001). Carabin also conferred protection against adrenergic receptor-induced hypertrophy in isolated cardiomyocytes. Mechanistically, Carabin carries out a tripartite suppressive function. Indeed, Carabin, through its calcineurin-interacting site and Ras/Rab GTPase-activating protein domain, functions as an endogenous inhibitor of calcineurin and Ras/extracellular signal-regulated kinase prohypertrophic signaling. Moreover, Carabin reduced Ca(2+)/calmodulin-dependent protein kinase II activation and prevented nuclear export of histone deacetylase 4 after adrenergic stimulation or myocardial pressure overload. Finally, we showed that Carabin Ras-GTPase-activating protein domain and calcineurin-interacting domain were both involved in the antihypertrophic action of Carabin. CONCLUSIONS: Our study identifies Carabin as a negative regulator of key prohypertrophic signaling molecules, calcineurin, Ras, and Ca(2+)/calmodulin-dependent protein kinase II and implicates Carabin in the development of cardiac hypertrophy and failure.

Role for DNA repair factor XRCC4 in immunoglobulin class switch recombination.

V(D)J recombination and immunoglobulin class switch recombination (CSR) are two somatic rearrangement mechanisms that proceed through the introduction of double-strand breaks (DSBs) in DNA. Although the DNA repair factor XRCC4 is essential for the resolution of DNA DSB during V(D)J recombination, its role in CSR has not been established. To bypass the embryonic lethality of XRCC4 deletion in mice, we developed a conditional XRCC4 knockout (KO) using LoxP-flanked XRCC4 cDNA lentiviral transgenesis. B lymphocyte restricted deletion of XRCC4 in these mice lead to an average two-fold reduction in CSR in vivo and in vitro. Our results connect XRCC4 and the nonhomologous end joining DNA repair pathway to CSR while reflecting the possible use of an alternative pathway in the repair of CSR DSB in the absence of XRCC4. In addition, this new conditional KO approach should be useful in studying other lethal mutations in mice.

Granulomatous disease in CVID: retrospective analysis of clinical characteristics and treatment efficacy in a cohort of 59 patients.

BACKGROUND: Granulomatous disease (GD) will develop in a subset of patients with common variable immunodeficiency (CVID). Little is known about the efficacy of therapeutic agents used for treating this disorder. OBJECTIVE: To evaluate the efficacy of immunosuppressive drugs with the help of a set of clinical, biological and radiological criteria. METHOD: Clinical and laboratory features of CVID patients were collected from the French DEFI cohort, a prospective study on adults with hypogammaglobulinemia. The medical charts of 55 patients (93 %) of the GD cohort were reviewed. RESULTS: Among 436 subjects with CVID, 59 patients (13.5 %) were diagnosed with GD. Of the 55 patients in whom medical charts were available, 32 patients received treatment for the granulomatous disease. Corticosteroids were the most frequently used drug. Complete response to treatment was infrequent. It was achieved with corticosteroids, cyclophosphamide, hydroxychloroquine, rituximab and methotrexate. Azathioprine, cyclosporine, mycophenolate mofetil, sirolimus, infliximab and thalidomide led to partial or absence of response. Complete and partial responses were observed in lymph nodes, lungs, liver, skin, bone marrow and central nervous system. Absent of response for gastrointestinal tract granulomas was noted in all cases of treatment attempt. CONCLUSION: CVID patients with GD exhibit a particular biological phenotype. Treatment should be considered in any symptomatic patient or if there is evidence of organ dysfunction. Corticosteroids are the drug of choice in most instances but response to treatment is often unsatisfactory.

Synovial fibroblasts promote immunoglobulin class switching by a mechanism involving BAFF.

Fibroblast-like synoviocytes (FLSs) are important actors in rheumatoid arthritis (RA) pathogenesis. The autoimmune nature of RA is attributed to autoantibody production, which confers to B cells a predominant role in RA. Several arguments support an induction of class switch recombination (CSR) in RA synovium, causing--in conjunction with somatic hypermutation--the production of potentially pathogenic IgG. To determine whether RA FLSs can directly promote CSR and to analyze the role of external factors like TLR signals and BAFF (B cell activating factor) family cytokines in this FLS-B cell crosstalk, we performed cocultures of blood B cells (from normal individuals or RA patients) with RA FLSs and analyzed CSR induction by quantification of AICDA (encoding activation-induced cytidine deaminase, AID) and switch circular transcripts expression, and IgG secretion. RA FLSs--and to a lesser extent osteoarthritis or control FLSs--promoted CSR, and TLR3 stimulation potentialized it. In addition, induction of CSR by RA FLSs was totally dependent on cell-cell contact in basal conditions, and partially dependent in the case of TLR3 stimulation. Finally, we showed that the mechanism by which RA FLSs induce CSR is mostly BAFF-dependent. Our results support the hypothesis that CSR can be induced outside the ectopic lymphoid structures in RA.

CD4 T cell-intrinsic STING signaling controls the differentiation and effector functions of TH1 and TH9 cells.

BACKGROUND: While stimulator of interferon genes (STING) activation in innate immune cells of the tumor microenvironment can result in CD8 T cell-dependent antitumor immunity, whether STING signaling affects CD4 T-cell responses remains elusive. METHODS: Here, we tested whether STING activation modulated the effector functions of CD4 T cells in vivo by analyzing tumor-infiltrating CD4 T cells and evaluating the contribution of the CD4 T cell-derived cytokines in the antitumor activity of the STING ligand 2'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) in two mouse tumor models. We performed ex vivo experiments to assess the impact of STING activation on CD4 T-cell differentiation and investigate the underlying molecular mechanisms. Finally, we tested whether STING activation enhances TH9 cell antitumor activity against mouse melanoma upon adoptive transfer. RESULTS: We found that activation of STING signaling cell-intrinsically enhances the differentiation and antitumor functions of TH1 and TH9 cells by increasing their respective production of interferon gamma (IFN-γ) and interleukin-9. IRF3 and type I interferon receptors (IFNARs) are required for the STING-driven enhancement of TH1 cell differentiation. However, STING activation favors TH9 cell differentiation independently of the IFNARs/IRF3 pathway but through mammalian target of rapamycin (mTOR) signaling, underscoring that STING activation differentially affects the fate of distinct CD4 T-cell subsets. The therapeutic effect of STING activation relies on TH1 and TH9-derived cytokines, and STING activation enhances the antitumor activity of TH9 cells upon adoptive transfer. CONCLUSION: Our results reveal the STING signaling pathway as a therapeutic target to boost CD4 T-cell effector functions and antitumor immunity.

Reduced immunoglobulin class switch recombination in the absence of Artemis.

Nonhomologous end-joining DNA repair factors, including Artemis, are all required for the repair of DNA double-strand breaks, which occur during the assembly of the variable antigen recognition domain of B-cell receptors and T-cell receptors through the V(D)J recombination. Mature B cells further shape their immunoglobulin repertoire on antigen recognition notably through the class switch recombination (CSR) process. To analyze the role of Artemis during CSR, we developed a mature B-cell-specific Artemis conditional knockout mouse to bypass the absence of B cells caused by its early deficit. Although CSR is not overwhelmingly affected in these mice, class switching to certain isotypes is clearly reduced both in vitro on B-cell activation and in vivo after keyhole limpet hemocyanin immunization. The reduced CSR in Artemis-deficient B cells is accompanied by the increase in DNA microhomology usage at CSR junctions, the imprint of an alternative DNA end-joining pathway. Likewise, significant increase in DNA microhomology usage is the signature of CSR junctions obtained from human RS-SCID patients harboring hypomorphic Artemis mutations. Altogether, this indicates that Artemis participates in the repair of a subset of DNA breaks generated during CSR.

Peripheral B cell abnormalities in patients with systemic lupus erythematosus in quiescent phase: decreased memory B cells and membrane CD19 expression.

B lymphocytes from patients with systemic lupus erythematosus (SLE) are hyperactive and produce autoantibodies. Several B cell phenotype characteristics such as the expansion of activated populations, and of a newly identified memory compartment have already been reported. These results are not easy to interpret because of the clinical heterogeneity of SLE, as well as the difficulties to establish homogeneous and well defined groups taking in consideration the activity of the disease and the various therapies. However, although many mediators and mechanisms can contribute to the clinical presentation and subsequent progression of individuals with SLE, several data suggest that some intrinsic B cells abnormalities may be central to the disease process. In this view, we have analysed the phenotype of B cells from 18 patients with quiescent diseases (mean SLEDAI score below 2) and from 11 healthy controls. B cell surface marker expression was determined by flow cytometry. We analysed the main B cell sub-populations. We demonstrate the persistence of plasmocyte-differentiated and -activated B cells even in quiescent patients. However, quiescent patients display a decrease in memory B cells that could reflect the control of their disease. Above all, we describe a lower membrane expression of the CD19 protein on all B cells in every patient compared to controls. This lower CD19 expression is associated with reduced CD45 levels. It is not associated with an evident gene expression alteration and in vitro stimulation restores a control phenotype. These findings suggest certain mechanisms of lupus development.

Stable and functional lymphoid reconstitution in artemis-deficient mice following lentiviral artemis gene transfer into hematopoietic stem cells.

Patients with mutations in the Artemis gene display a complete absence of T- and B lymphocytes, together with increased cellular radiosensitivity; this leads to a radiosensitive severe combined immunodeficiency (RS-SCID). Allogenic hematopoietic stem-cell (HSC) transplantation is only partially successful in the absence of an human leukocyte antigen-genoidentical donor, and this has prompted a search for alternative therapeutic approaches such as gene therapy. In this study, a self-inactivated lentiviral vector expressing Artemis was used to complement the Artemis knockout mouse (Art(-/-)). Transplantation of Artemis-transduced HSCs into irradiated Art(-/-) mice restored a stable (over a 15-month period of follow-up) and functional T- and cell repertoire that was comparable to that of control mice. The success of secondary transplantations demonstrated that the HSCs had been transduced. One of thirteen mice developed a thymoma 6 months after gene therapy. Although thymic cells were seen to be carrying two lentiviral integration sites, there was no evidence of lentivirus-driven oncogene activation. The Art(-/-) mice were found to be prone to develop T-cell lymphomas, either spontaneously or after irradiation. These data indicate that the observed lymphoproliferation was probably the consequence of the chromosomal instability associated with the Artemis-deficient background. As a whole, our work provides a basis for supporting the gene therapy approach in Artemis-deficient SCID.

Monogenic lupus: Dissecting heterogeneity.

Systemic lupus erythematosus (SLE) is a severe lifelong multisystem autoimmune disease characterized by the presence of autoantibodies targeting nuclear autoantigens, increased production of type I interferon and B cell abnormalities. Clinical presentation of SLE is extremely heterogeneous and different groups of disease are likely to exist. Recently, childhood-onset SLE (cSLE) cases have been linked to single gene mutations, defining the concept of monogenic or Mendelian lupus. Genes associated with Mendelian lupus can be grouped in at least three functional categories. First, complement deficiencies represent the main cause of monogenic lupus and its components are involved in the clearance of dying cells, a mechanism also called efferocytosis. Mutations in extracellular DNASE have been also identified in cSLE patients and represent additional causes leading to defective clearance of nucleic acids and apoptotic bodies. Second, the study of Aicardi-Goutières syndromes has introduced the concept of type-I interferonopathies. Bona fide lupus syndromes have been associated to this genetic condition, driven by defective nucleic acids metabolism or innate sensors overactivity. Interferon signalling anomalies can be detected and monitored during therapies, such as Janus-kinase (JAK) inhibitors. Third, tolerance breakdown can occur following genetic mutations in B and/or T cell expressing key immunoregulatory molecules. Biallelic mutations in PRKCD are associated to lupus and lymphoproliferative diseases as PKC-δ displays proapoptotic activity and is crucial to eliminate self-reactive transitional B cells. Here we review the literature of the emerging field of Mendelian lupus and discuss the physiopathological learning from these inborn errors of immunity. In addition, clinical and biological features are highlighted as well as specific therapies that have been tested in these genetic contexts.

10 most important contemporary challenges in the management of SLE.

From a 1-year survival of less than 50% before the discovery of glucocorticoids to over 90% at 10 years in most dedicated centres, the spectrum of SLE has profoundly evolved. Despite this improvement, several major challenges currently remain. The aim of this review is to analyse what are, according to us, the 10 most important contemporary challenges in the management of SLE. Among those are the need to treat to target to favour disease remission (or low disease activity), limit the use of glucocorticoids, derive more comprehensive tools for the evaluation of disease activity, develop more effective drugs (yielding successful trials), dissect the heterogeneity of the disease both at the molecular and genetic levels, identify relevant biomarkers for individualised treatment, manage fertility and pregnancy, tackle comorbidities such as cardiovascular risk, the prevention of infections and osteoporosis, improve the network of care (from the patients' perspective), and favour a holistic approach (integrating fatigue, adherence to treatment, physical activity). Altogether, these 10 contemporary challenges in SLE may be considered as a roadmap for those involved in the daily care of patients with SLE, as well as for researchers who may wish to contribute to an improved management of this rare and complex disease.