6-Sulfo LacNAc monocytes are quantitatively and functionally disturbed in systemic sclerosis patients.

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis, microangiopathy, and autoantibodies. We previously reported that circulating follicular helper T (cTfh) cells are increased in SSc and induce plasmablast differentiation. However, mechanisms leading to cTfh cell expansion and activation in SSc remain to be established. Tfh cells require IL-12 for their expansion and differentiation. 6-Sulfo LacNAc monocytes (slanMo), a subset of monocytes, have a higher capacity to produce IL-12 and to induce CD4+ T cell proliferation in comparison with dendritic cells (DC) or classical monocytes. The aim of this study was to perform a quantitative and functional analysis of monocytes and DC and to correlate them with cTfh cell expansion and clinical manifestations in SSc. Using flow cytometry, we analyzed different monocyte subsets including slanMo and DC from 36 SSc patients and 26 healthy controls (HC). In vitro culture experiments of sorted slanMo were performed for functional analysis and cytokine production. We observed that slanMo, intermediate and non-classical monocytes were increased in SSc in comparison with HC. Furthermore, the increase in slanMo cells was more potent in patients with diffuse SSc. We observed a significant positive correlation between slanMo and cTfh cell levels in SSc patients but not in HC. Other monocyte subsets did not correlate with cTfh cell expansion. In addition, we observed that in vitro, slanMo cells from SSc patients produced less IL-12 than slanMo from HC. SlanMo are increased in SSc and may participate in the activation of cTfh cells in SSc.

Clonal haematopoiesis is increased in early onset in systemic sclerosis.

OBJECTIVES: SSc is an autoimmune disease characterized by fibrosis, microangiopathy and immune dysfunctions including dysregulation of proinflammatory cytokines. Clonal haematopoiesis of indeterminate potential (CHIP) is defined by the acquisition of somatic mutations in haematopoietic stem cells leading to detectable clones in the blood. Recent data have shown a higher risk of cardiovascular disease in patients with CHIP resulting from increased production of proinflammatory cytokines and accelerated atherosclerosis. Eventual links between CHIP and autoimmune diseases are undetermined. The aim of our study was to evaluate the prevalence of CHIP in SSc patients and its association with clinical phenotype. METHODS: Forty-one genes frequently mutated in myeloid malignancies were sequenced in peripheral blood mononuclear cells from 90 SSc patients and 44 healthy donors. RESULTS: A total of 15 somatic variants were detected in 13/90 SSc patients (14%) and four somatic variants in 4/44 (9%) healthy donors (HD) (P = 0.58). The prevalence of CHIP was significantly higher in younger SSc patients than in HD: 25% (6/24) vs 4% (1/26) (P = 0.045) under 50 years and 17% (7/42) vs 3% (1/38) (P = 0.065) under 60 years. The prevalence of CHIP in patients over 70 years was similar in SSc patients and healthy donors. The most common mutations occurred in DNMT3A (seven variants). No major clinical differences were observed between SSc patients with or without CHIP. CONCLUSION: Whether CHIP increases the risk to develop SSc or is a consequence of a SSc-derived modified bone marrow micro-environment remains to be explored.

Arsenic trioxide induces regulatory functions of plasmacytoid dendritic cells through interferon- α inhibition.

Arsenic trioxide (As2O3) is recently found to have therapeutic potential in systemic sclerosis (SSc), a life-threatening multi-system fibrosing autoimmune disease with type I interferon (IFN-I) signature. Chronically activated plasmacytoid dendritic cells (pDCs) are responsible for IFN-I secretion and are closely related with fibrosis establishment in SSc. In this study, we showed that high concentrations of As2O3 induced apoptosis of pDCs via mitochondrial pathway with increased BAX/BCL-2 ratio, while independent of reactive oxygen species generation. Notably, at clinical relevant concentrations, As2O3 preferentially inhibited IFN-α secretion as compared to other cytokines such as TNF-α, probably due to potent down-regulation of the total protein and mRNA expression, as well as phosphorylation of the interferon regulatory factor 7 (IRF7). In addition, As2O3 induced a suppressive phenotype, and in combination with cytokine inhibition, it down-regulated pDCs' capacity to induce CD4+ T cell proliferation, Th1/Th22 polarization, and B cell differentiation towards plasmablasts. Moreover, chronically activated pDCs from SSc patients were not resistant to the selective IFN-α inhibition, and regulatory phenotype induced by As2O3. Collectively, our data suggest that As2O3 could target pDCs and exert its treatment efficacy in SSc, and more autoimmune disorders with IFN-I signature.

Daratumumab prevents programmed death ligand-1 expression on antigen-presenting cells in de novo multiple myeloma.

BACKGROUND: Daratumumab (Dara), an anti-CD38 monoclonal antibody, has an immunologic mechanism of action through targeting of CD38 expressing immune cells in patients with multiple myeloma (MM). Furthermore, it was recently shown that CD38 upregulation in tumors, is a major mechanism of acquired resistance to antiprogrammed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1). Therefore, we decided to evaluate the immunomodulatory effects of CD38 blockade by Dara on the PD-L1 expressing immune cells. METHODS: We analyzed CD38 and PD-L1 expression on immune cells at different time points in 18 newly diagnosed MM receiving bortezomib, lenalidomide and dexamethasone, with or without Dara. RESULTS: We first confirmed that CD38 is widely expressed on immune cells, with the strongest expression on plasmacytoid dendritic cells (pDC). Furthermore, Dara induces a strong depletion of pDC in addition to the well-known rapid depletion of natural killer cells. Finally, we found that PD-L1 expression on antigen-presenting cells (APC) increases with MM treatment in patients that did not received Dara, while addition of Dara prevents this increase. CONCLUSION: Overall, our results suggest new mechanisms of action of Dara through depletion of pDC and prevention of PD-L1 upregulation expression on APC. Our finding provides new evidences for development of therapeutic strategies targeting both CD38 and PD-L1/PD-1 pathway in patients with MM.

Quantitative and functional alterations of 6-sulfo LacNac dendritic cells in multiple myeloma.

Multiple myeloma (MM) results from expansion of abnormal plasma cells in the bone marrow (BM). Previous studies have shown that monocytes play a crucial role in MM pathophysiology. A 6-sulfo LacNAc-expressing population of dendritic cells (Slan-DCs) that overlaps with intermediate and non-classical monocytes in terms of phenotype has been described. Slan-DCs represent a circulating and tissue proinflammatory myeloid population which has been shown to play a role in different cancer contexts, and which exhibits a remarkable plasticity. Herein, we studied Slan-DCs from the BM and blood of MM patients. We performed quantitative and functional analyses of these cells from 54 patients with newly diagnosed, symptomatic MM, 21 patients with MGUS and 24 responding MM patients. We found that circulating Slan-DCs were significantly decreased in MM patients as compared to those of healthy donors or patients with MGUS, while CD14+CD16+ intermediate monocytes accumulate in the BM. Moreover, after activation with TLR7/8 ligand R848, IL-12-producing Slan-DCs from the BM or peripheral blood from MM patients were decreased as compared with healthy donors. We show that MM cell lines or MM cells isolated from patients at diagnosis were able to inhibit the production of IL-12 by Slan-DCs, as well as to shift the phenotype of Slan-DCs towards an intermediate monocyte-like phenotype. Finally, Slan-DCs that have been cultured with MM cells reduced their capacity to induce T cell proliferation and Th1 polarization. We conclude that Slan-DCs represent previously unrecognized players in MM development and may represent a therapeutic target.