Measurement of circulating CD21-CD27- B lymphocytes in SLE patients is associated with disease activity independently of conventional serological biomarkers.

Determining disease activity in systemic lupus erythematosus (SLE) patients is challenging and limited by the lack of reliable biomarkers. Abnormally activated B cells play a key role in the pathogenesis of SLE, but their measure in clinical practice is currently not recommended. Here, we studied peripheral B cells to identify a valid biomarker. We analyzed peripheral B cells in a discovery cohort of 30 SLE patients compared to 30 healthy controls (HC) using mass cytometry and unsupervised clustering analysis. The relevant B cell populations were subsequently studied by flow cytometry in a validation cohort of 63 SLE patients, 28 autoimmune diseases controls and 39 HC. Our data show an increased frequency of B cell populations with activated phenotype in SLE compared to healthy and autoimmune diseases controls. These cells uniformly lacked the expression of CD21 and CD27. Measurement of CD21-CD27- B cells in the blood identified patients with active disease and their frequency correlated with disease severity. Interestingly, we did not observe an increase in the frequency of CD21-CD27- B cells in patients with clinically inactive disease but with elevated conventional biomarkers (anti-dsDNA and complement levels). Accordingly, measurement of CD21-CD27- B cells represents a robust and easily accessible biomarker to assess the activity of the disease in SLE patients.

SLAMF Receptor Expression Identifies an Immune Signature That Characterizes Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology, linked to alterations in both the innate and the adaptive immune system. Due to the heterogeneity of the clinical presentation, the diagnosis of SLE remains complicated and is often made years after the first symptoms manifest, delaying treatment, and worsening the prognosis. Several studies have shown that signaling lymphocytic activation molecule family (SLAMF) receptors are aberrantly expressed and dysfunctional in SLE immune cells, contributing to the altered cellular function observed in these patients. The aim of this study was to determine whether altered co-/expression of SLAMF receptors on peripheral blood mononuclear cells (PBMC) identifies SLE characteristic cell populations. To this end, single cell mass cytometry and bioinformatic analysis were exploited to compare SLE patients to healthy and autoimmune diseases controls. First, the expression of each SLAMF receptor on all PBMC populations was investigated. We observed that SLAMF1+ B cells (referred to as SLEB1) were increased in SLE compared to controls. Furthermore, the frequency of SLAMF4+ monocytes and SLAMF4+ NK were inversely correlated with disease activity, whereas the frequency SLAMF1+ CD4+ TDEM cells were directly correlated with disease activity. Consensus clustering analysis identified two cell clusters that presented significantly increased frequency in SLE compared to controls: switch memory B cells expressing SLAMF1, SLAMF3, SLAMF5, SLAMF6 (referred to as SLESMB) and circulating T follicular helper cells expressing the same SLAMF receptors (referred to as SLEcTFH). Finally, the robustness of the identified cell populations as biomarkers for SLE was evaluated through ROC curve analysis. The combined measurement of SLEcTFH and SLEB1 or SLESMB cells identified SLE patients in 90% of cases. In conclusion, this study identified an immune signature for SLE based on the expression of SLAMF receptors on PBMC, further highlighting the involvement of SLAMF receptors in the pathogenesis of SLE.

Restoration of NK Cell Cytotoxic Function With Elotuzumab and Daratumumab Promotes Elimination of Circulating Plasma Cells in Patients With SLE.

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by multiple cellular and molecular dysfunctions of the innate and adaptive immunity. Cytotoxic function of NK cells is compromised in patients with SLE. Herein, we characterized the phenotypic alterations of SLE NK cells in a comprehensive manner to further delineate the mechanisms underlying the cytotoxic dysfunction of SLE NK cells and identify novel potential therapeutic targets. Therefore, we examined PBMC from SLE patients and matched healthy controls by single-cell mass cytometry to assess the phenotype of NK cells. In addition, we evaluated the cell function of NK cells (degranulation and cytokine production) and the killing of B cell subpopulations in a B cell-NK cell in vitro co-culture model. We found that SLE NK cells expressed higher levels of CD38 and were not able to adequately upregulate SLAMF1 and SLAMF7 following activation. In addition, ligation of SLAMF7 with elotuzumab or of CD38 with daratumumab on SLE NK cells enhanced degranulation of both healthy and SLE NK cells and primed them to kill circulating plasma cells in an in vitro co-culture system. Overall, our data indicated that dysregulated expression of CD38, SLAMF1 and SLAMF7 on SLE NK cells is associated with an altered interplay between SLE NK cells and plasma cells, thus suggesting their contribution to the accumulation of (auto)antibody producing cells. Accordingly, targeting SLAMF7 and CD38 may represent novel therapeutic approaches in SLE by enhancing NK cell function and promoting elimination of circulating plasma cell.

Clinical spectrum and long-term follow-up of 14 cases with G6PC3 mutations from the French Severe Congenital Neutropenia Registry.

BACKGROUND: The purpose of this study was to describe the natural history of severe congenital neutropenia (SCN) in 14 patients with G6PC3 mutations and enrolled in the French SCN registry. METHODS: Among 605 patients included in the French SCN registry, we identified 8 pedigrees that included 14 patients with autosomal recessive G6PC3 mutations. RESULTS: Median age at the last visit was 22.4 years. All patients had developed various comordibities, including prominent veins (n = 12), cardiac malformations (n = 12), intellectual disability (n = 7), and myopathic syndrome with recurrent painful cramps (n = 1). Three patients developed Crohn's disease, and five had chronic diarrhea with steatorrhea. Neutropenia was profound (<0.5 × 109/l) in almost all cases at diagnosis and could marginally fluctuate. The bone marrow smears exhibited mild late-stage granulopoeitic defects. One patient developed myelodysplasia followed by acute myelogenous leukemia with translocation (18, 21) at age 14 years, cured by chemotherapy and hematopoietic stem cell transplantation. Four deaths occurred, including one from sepsis at age 5, one from pulmonary late-stage insufficiency at age 19, and two from sudden death, both at age 30 years. A new homozygous mutation (c.249G > A /p.Trp83*) was detected in one pedigree. CONCLUSIONS: Severe congenital neutropenia with autosomal recessive G6PC3 mutations is associated with considerable clinical heterogeneity. This series includes the first described case of malignancy in this neutropenia.

CD160-associated CD8 T-cell functional impairment is independent of PD-1 expression.

Expression of co-inhibitory molecules is generally associated with T-cell dysfunction in chronic viral infections such as HIV or HCV. However, their relative contribution in the T-cell impairment remains unclear. In the present study, we have evaluated the impact of the expression of co-inhibitory molecules such as 2B4, PD-1 and CD160 on the functions of CD8 T-cells specific to influenza, EBV and CMV. We show that CD8 T-cell populations expressing CD160, but not PD-1, had reduced proliferation capacity and perforin expression, thus indicating that the functional impairment in CD160(+) CD8 T cells may be independent of PD-1 expression. The blockade of CD160/CD160-ligand interaction restored CD8 T-cell proliferation capacity, and the extent of restoration directly correlated with the ex vivo proportion of CD160(+) CD8 T cells suggesting that CD160 negatively regulates TCR-mediated signaling. Furthermore, CD160 expression was not up-regulated upon T-cell activation or proliferation as compared to PD-1. Taken together, these results provide evidence that CD160-associated CD8 T-cell functional impairment is independent of PD-1 expression.

Exhaustion of bacteria-specific CD4 T cells and microbial translocation in common variable immunodeficiency disorders.

In the present study, we have investigated the functional profile of CD4 T cells from patients with common variable immunodeficiency (CVID), including production of cytokines and proliferation in response to bacteria and virus-derived antigens. We show that the functional impairment of CD4 T cells, including the reduced capacity to proliferate and to produce IFN-γ and IL-2, was restricted to bacteria-specific and not virus-specific CD4 T cells. High levels of endotoxins were found in the plasma of patients with CVID, suggesting that CD4 T cell dysfunction might be caused by bacterial translocation. Of note, endotoxemia was associated with significantly higher expression of programmed death 1 (PD-1) on CD4 T cells. The blockade of the PD-1-PD-L1/2 axis in vitro restored CD4 T cell proliferation capacity, thus indicating that PD-1 signaling negatively regulates CD4 T cell functions. Finally, we showed that intravenous immunoglobulin G (IVIG) treatment significantly reduced endotoxemia and the percentage of PD-1(+) CD4 T cells, and restored bacteria-specific CD4 T cell cytokine production and proliferation. In conclusion, the present study demonstrates that the CD4 T cell exhaustion and functional impairment observed in CVID patients is associated with bacterial translocation and that IVIG treatment resolves bacterial translocation and restores CD4 T cell functions.

Classification of and risk factors for hematologic complications in a French national cohort of 102 patients with Shwachman-Diamond syndrome.

BACKGROUND: Patients with the Shwachman-Diamond syndrome often develop hematologic complications. No risk factors for these complications have so far been identified. The aim of this study was to classify the hematologic complications occurring in patients with Shwachman-Diamond syndrome and to investigate the risk factors for these complications. DESIGN AND METHODS: One hundred and two patients with Shwachman-Diamond syndrome, with a median follow-up of 11.6 years, were studied. Major hematologic complications were considered in the case of definitive severe cytopenia (i.e. anemia <7 g/dL or thrombocytopenia <20 × 10(9)/L), classified as malignant (myelodysplasia/leukemia) according to the 2008 World Health Organization classification or as non-malignant. RESULTS: Severe cytopenia was observed in 21 patients and classified as malignant severe cytopenia (n=9), non-malignant severe cytopenia (n=9) and malignant severe cytopenia preceded by non-malignant severe cytopenia (n=3). The 20-year cumulative risk of severe cytopenia was 24.3% (95% confidence interval: 15.3%-38.5%). Young age at first symptoms (<3 months) and low hematologic parameters both at diagnosis of the disease and during the follow-up were associated with severe hematologic complications (P<0.001). Fifteen novel SBDS mutations were identified. Genotype analysis showed no discernible prognostic value. CONCLUSIONS Patients with Shwachman-Diamond syndrome with very early symptoms or cytopenia at diagnosis (even mild anemia or thrombocytopenia) should be considered at a high risk of severe hematologic complications, malignant or non-malignant. Transient severe cytopenia or an indolent cytogenetic clone had no deleterious value.

Genetic and clinical implications of the Val617Phe JAK2 mutation in 72 families with myeloproliferative disorders.

To study the prevalence of the Val617Phe JAK2 mutation in familial cases of myeloproliferative disorder (MPD) and its possible implication as a predisposing genetic factor, we analyzed 72 families including 174 patients (81 polycythemia vera [PV], 68 essential thrombocythemia [ET], 11 myelofibrosis with myeloid metaplasia [MMM], 12 chronic myeloid leukemia), 1 systemic mastocytosis, and 1 chronic myelomonocytic leukemia (CMML). The JAK2 mutation was found in three quarters of patients with PV and MMM and in half of patients with ET. Among 46 families with at least 2 cases of PV, ET, or MMM, the JAK2 mutation was absent in 6 families, heterogeneously distributed in 18, and present in all MPD patients in 22. Among these 22 families, the absence of the JAK2 mutation both in purified T and B cells in 13 unrelated patients and the observation of variable ratios of the JAK2 mutant allele in patient leucocytes indicated that the Val617Phe JAK2 mutation was acquired in familial MPDs. The JAK2 mutation was present in natural killer cells in two thirds of tested patients (27 of 40), suggesting its occurrence in a multipotent hematopoietic progenitor cell. The analysis of the hematologic profile showed that the homozygous JAK2 mutation confers a proliferative advantage and is associated with the progression of the hematologic disease.