Unconventional T Cells Influence Clinical Outcome After Allogeneic Hematopoietic Cell Transplantation.

We evaluated the impact of early recovery of mucosal-associated invariant T cells (MAIT) and gamma-delta (γδ) T cells, especially Vδ2+ T cells, on the clinical outcomes of 76 patients who underwent allogeneic hematopoietic cell transplantation (allo-HCT). MAIT cells were identified at day 20-30 post-transplant using flow cytometry and defined as CD3+ TCRVα7.2+CD161+. Two subsets of Vδ2+ T cells were analyzed according to the expression of CD26. The cytotoxicity profile of MAIT and Vδ2+ T cells was analyzed according to the intracellular expression of perforin and granzyme B, and intracellular IFN-γ was evaluated after in vitro activation. CD26+Vδ2+ T cells displayed higher intracellular levels of IFN-γ, whereas CD26- Vδ2+ T were found to be more cytotoxic. Moreover, MAIT cell frequency was correlated with the frequency of Vδ2+ T cells with a better correlation observed with Vδ2+CD26+ than with the Vδ2+CD26- T cell subset. By using the composite endpoint graft-versus-host disease (GvHD)-free, relapse-free survival (GRFS) as the primary endpoint, we found that patients with a higher MAIT cell frequency at day 20-30 after allo-HCT had a significantly increased GRFS and a better overall survival (OS) and disease-free survival (DFS). Moreover, patients with a low CD69 expression by MAIT cells had an increased cumulative incidence of grade 2-4 acute GvHD (aGvHD). These results suggest that MAIT cell reconstitution may provide mitigating effects early after allo-HCT depending on their activation markers and functional status. Patients with a high frequency of Vδ2+CD26+ T cells had a significantly higher GRFS, OS and DFS, but there was no impact on cumulative incidence of grade 2-4 aGVHD, non-relapse mortality and relapse. These results revealed that the impact of Vδ2+ T cells on the success of allo-HCT may vary according to the frequency of the CD26+ subset.

Photobiomodulation: a promising innovative approach for preventing oral mucositis in patients undergoing hematopoietic stem cell transplantation.

PURPOSE: This single-center retrospective study aims to assess the feasibility, safety, and tolerability of CareMin650, a new photobiomodulation device, for both preventing oral mucositis (OM) and reducing its severity in the setting of hematopoietic stem cell transplantation (HCT). METHODS: Patients who underwent autologous HCT for hematological malignancies between November 2020 and October 2021 could be included. Prophylactic photobiomodulation (PBM) was used daily from day 1 of conditioning until the day of neutrophil recovery at a dose of 3 J/cm2. Curative PBM was started at a dose of 6 J/cm2 when at least one grade 1 OM had occurred. For each OM case, time of onset, National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE) v5.0 grade for OM, analgesic dose, and time to resolution were reported. RESULTS: Twenty-five consecutive patients were included. The median age was 58 years (range, 39-74) and 14 (56%) were male. Twenty-one patients (84%) received a high-dose melphalan conditioning regimen for multiple myeloma, and 4 (16%) patients received BEAM conditioning for aggressive lymphoma. A total of 178 CareMin650 sessions were performed, with a median of 7 days of application (range, 4-12), with no device-related adverse events (AEs). According to the NCI-CTCAE v5.0 scale, 76% (19 of 25) of patients presented grade 0 or 1 mucositis (no ulcers), five patients (20%) developed small ulcers (grade 2), and only one patient developed grade 4 mucositis. Satisfaction rates were high among patients and users. CONCLUSION: Photobiomodulation provides excellent safety and tolerance, as well as promising efficacy, both as a preventive and curative strategy, in patients undergoing autologous HCT.

Circulating follicular helper T cells are increased in systemic sclerosis and promote plasmablast differentiation through the IL-21 pathway which can be inhibited by ruxolitinib.

OBJECTIVES: Systemic sclerosis (SSc) is an autoimmune disease characterised by widespread fibrosis, microangiopathy and autoantibodies. Follicular helper T (Tfh) cells CD4+CXCR5+PD-1+ cooperate with B lymphocytes to induce the differentiation of plasmocytes secreting immunoglobulins (Ig). Circulating Tfh (cTfh) cells are increased in several autoimmune diseases. However, there are no data about cTfh cells and their interaction with B cells in SSc. The aim of this study was to perform a quantitative and functional analysis of cTfh cells in SSc. METHODS: Using flow cytometry, we analysed cTfh cells from 50 patients with SSc and 32 healthy controls (HC). In vitro coculture experiments of sorted cTfh and B cells were performed for functional analysis. IgG and IgM production were measured by ELISA. RESULTS: We observed that cTfh cell numbers are increased in patients with SSc compared with HC. Furthermore, the increase in cTfh cells was more potent in patients with severe forms of SSc such as diffuse SSc and in the presence of arterial pulmonary hypertension. cTfh cells from patients with SSc present an activated Tfh phenotype, with high expression of BCL-6, increased capacity to produce IL-21 in comparison with healthy controls. In vitro, cTfh cells from patients with SSc had higher capacity to stimulate the differentiation of CD19+CD27+CD38hi B cells and their secretion of IgG and IgM through the IL-21 pathway than Tfh cells from healthy controls. Blocking IL-21R or using the JAK1/2 inhibitor ruxolitinib reduced the Tfh cells' capacity to stimulate the plasmablasts and decreased the Ig production. CONCLUSIONS: Circulating Tfh cells are increased in SSc and correlate with SSc severity. The IL-21 pathway or JAK1/2 blockade by ruxolitinib could be a promising strategy in the treatment of SSc.

Impact of cyclosporine A concentration on acute graft-vs-host disease incidence after haploidentical hematopoietic cell transplantation.

OBJECTIVES: This retrospective study analyzed the impact of early cyclosporine A (CsA) initiation (day -3) on the risk of acute graft-vs-host disease (aGvHD) after haploidentical hematopoietic cell transplantation (Haplo-HCT) using post-transplant cyclophosphamide. METHODS: Sixty-one consecutives patients who underwent Haplo-HCT were analyzed. RESULTS: At day +180, the cumulative incidences of grade II-IV and grade III-IV aGvHD were 39% and 18%, respectively. Patients having a lowest CsA concentration (<301 ng/mL; the cutoff value used to segregate the patients between low and high CsA concentrations) in the first week after Haplo-HCT had a significantly higher risk of grade II-IV aGvHD (P = 0.02), severe grade III-IV aGvHD (P = 0.03), cGvHD (P = 0.02), and extensive cGvHD (P = 0.04). In multivariate analysis, a higher CsA concentration (≥301 ng/mL) during the first week following Haplo-HCT was the only parameter significantly associated with a reduced risk of grade II-IV and grade III-IV aGvHD (RR = 0.21; P = 0.049 and RR < 0.001; P < 0.0001, respectively). We find no correlation between CsA concentration and relapse, non-relapse mortality, progression-free survival, GvHD-free and progression-free survival, or overall survival. CONCLUSIONS: CsA could be initiated early before Haplo-HCT with achievement of high CsA concentration to reduce the risk of aGvHD without any detrimental effect on relapse.

Bistable expression of virulence genes in salmonella leads to the formation of an antibiotic-tolerant subpopulation.

Phenotypic heterogeneity can confer clonal groups of organisms with new functionality. A paradigmatic example is the bistable expression of virulence genes in Salmonella typhimurium, which leads to phenotypically virulent and phenotypically avirulent subpopulations. The two subpopulations have been shown to divide labor during S. typhimurium infections. Here, we show that heterogeneous virulence gene expression in this organism also promotes survival against exposure to antibiotics through a bet-hedging mechanism. Using microfluidic devices in combination with fluorescence time-lapse microscopy and quantitative image analysis, we analyzed the expression of virulence genes at the single cell level and related it to survival when exposed to antibiotics. We found that, across different types of antibiotics and under concentrations that are clinically relevant, the subpopulation of bacterial cells that express virulence genes shows increased survival after exposure to antibiotics. Intriguingly, there is an interplay between the two consequences of phenotypic heterogeneity. The bet-hedging effect that arises through heterogeneity in virulence gene expression can protect clonal populations against avirulent mutants that exploit and subvert the division of labor within these populations. We conclude that bet-hedging and the division of labor can arise through variation in a single trait and interact with each other. This reveals a new degree of functional complexity of phenotypic heterogeneity. In addition, our results suggest a general principle of how pathogens can evade antibiotics: Expression of virulence factors often entails metabolic costs and the resulting growth retardation could generally increase tolerance against antibiotics and thus compromise treatment.

Bi- and Tri-specific antibodies in non-Hodgkin lymphoma: current data and perspectives.

Bispecific antibodies (BsAbs) are a new group of targeted therapies that are revolutionizing the treatment landscape of B-cell non-Hodgkin's lymphoma (B-NHL). In the relapsed/refractory setting, salvage chemotherapy and autologous stem cell transplantation are capable of curing 50% of patients, whereas the other half will have a dismal outcome with a median overall survival of less than 12 months. This unmet need reinforced the importance of innovative therapies like the BsAbs and CAR-T cell therapies. In this review, we delve into BsAbs in B-NHL from the preclinical development to clinical data in both refractory and frontline settings, and then discuss future perspectives.

A combination of 5-azacytidine and nivolumab is a potentially effective rescue therapy in relapsed/refractory AITL.

Introduction: Angioimmunoblastic T-cell lymphoma (AITL) is a peripheral T-cell lymphoma characterized by a T follicular helper cell phenotype expressing PD-1 (programmed cell death-1). AITL exhibits a poor response to conventional chemotherapy, with a median 5-year overall survival of 44% and a progression-free survival of 32%. Relapse is common, resulting in a median overall survival of 6 months. Recurrent mutations are detected in genes regulating DNA methylation, including TET2, DNMT3A, and IDH2 variants, along with the prevalent RHOA G17V mutation. In this context, patients treated with the hypomethylating agent 5-azacytidine achieved overall response and complete response rates of 75% and 41%, respectively. We hypothesized that targeted therapies combining anti-PD-1 checkpoint blockers with hypomethylating agents could be efficient in AITL patients and less toxic than standard chemotherapy. Methods: Here, we report the efficacy of a regimen combining 5-azacytidine and nivolumab in nine relapsed or refractory AITL patients. Results: This regimen was well-tolerated, especially in elderly patients. The overall response rate was 78%, including four partial responses (44%) and three complete responses (33%). Allogeneic hematopoietic stem cell transplantation was performed in two patients who reached complete response. Discussion: These preliminary favorable results may serve as a basis for further investigation in prospective studies.

Invasive Aspergillosis with impaired neutrophil responses against Aspergillus fumigatus in patients treated with Acalabrutinib-findings from three cases.

OBJECTIVES: Ibrutinib, a first-generation covalent Bruton's tyrosine kinase inhibitor (BTKi) was found to be a risk factor for the occurrence of invasive fungal complications. Acalabrutinib is a second-generation covalent BTKi used to treat B-cell malignancies. Healthy donor neutrophils incubated ex vivo with acalabrutinib lose ability to control Aspergillus conidia germination. In patients receiving acalabrutinib, the potential effect on neutrophil antifungal activity is unknown. Furthermore, only two cases of invasive aspergillosis have been reported during treatment with acalabrutinib, outside of a few cases in a clinical trial. METHODS: We describe three new cases of invasive aspergillosis occurring within the first months of acalabrutinib therapy in patients with chronic lymphocytic leukemia. We used videomicroscopy and flow cytometry approaches to investigate the basic functional responses against Aspergillus of neutrophils from acalabrutinib-treated patients. RESULTS: We showed an alteration in the anti-Aspergillus response after 1 month of acalabrutinb therapy: neutrophils lost their capacities of killing Aspergillus fumigatus germinating conidia and decreased their reactive oxygen species production when stimulated by Aspergillus. CONCLUSIONS: It is important to follow-up patients treated with acalabrutinib for the risk of aspergillosis as well as those treated with ibrutinib.

Human herpesvirus type 6 reactivation after haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide and antithymocyte globulin: risk factors and clinical impact.

Human herpesvirus type 6 (HHV6) reactivation after haploidentical hematopoietic cell transplantation (HCT) with post-transplant cyclophosphamide (PT-Cy) has been scarcely studied, especially when antithymocyte globulin (ATG) is added to the graft-versus-host disease (GvHD) prophylaxis. We conducted a retrospective cohort study in 100 consecutive patients receiving haploidentical HCT with PT-Cy. We systematically monitored HHV6 DNA loads in blood samples on a weekly basis using quantitative PCR until day +100. The 100-day cumulative incidence of HHV6 reactivation was 54%. Clinically significant HHV6 infections were rare (7%), associated with higher HHV6 DNA loads, and had favorable outcomes after antiviral therapy. The main risk factor for HHV6 reactivation was a low absolute lymphocyte count (ALC) \< 290/µL on day +30 (68% versus 40%, p = 0.003). Adding ATG to PT-Cy did not increase the incidence of HHV6 reactivation (52% with ATG versus 79% without ATG, p = 0.12). Patients experiencing HHV6 reactivation demonstrated delayed platelet recovery (HR 1.81, 95% CI 1.07-3.05, p = 0.026), higher risk of acute grade II-IV GvHD (39% versus 9%, p \< 0.001) but similar overall survival and non-relapse mortality to the other patients. In conclusion, our findings endorse the safety of combining ATG and PT-Cy in terms of the risk of HHV6 reactivation and infection in patients undergoing haploidentical HCT. Patients with a low ALC on day +30 face a higher risk of HHV6 reactivation and may require careful monitoring.

Coexistence of three hematological malignancies in association with a first time documented mutation: "One train can hide another"°, and even more!

Coexisting malignancies is not only an uncommon event but, it can also represent a medical challenge. Its complexity relies on the difficulty of management and the need for personalized and prioritized therapeutic approaches, on the one hand, and in the potential misdiagnosis of recurrence or even a de novo disease, on the other. Here, we present a case of a 69-year-old patient, who was initially diagnosed with a chronic myelomonocytic leukemia (CMML), followed by monoclonal gammopathy of uncertain significance (MGUS). Few years later, the patient developed Hodgkin's lymphoma (HL), and a new mutation, previously undocumented in the medical literature, was also detected. As a conclusion, we can say that the decision must be taken with caution and must be based on two major factors: 1- The rapid evolution of malignancies: give priority to treating the most rapid/life-threatening disease. 2- Prioritize the treatment of symptomatic disease and/or that which may most improve patients' quality of life.

Autologous hematopoietic cell transplantation as a part of a sequential multi-phase therapeutic approach (R-COPADM/CYVE/ASCT) as first-line treatment of high-grade B-cell lymphoma: results of a retrospective study with long-term follow-up.

Patients with high-risk lymphoma have a poor prognosis when treated with standard chemoimmunotherapy. This retrospective study included 23 high-risk lymphoma patients with a median age at diagnosis of 59 (range, 35-68) years. They received 2 cycles of R-COPADM and 2 cycles of CYVE, completed by ASCT for fit patients. With a median follow-up of 46 (range, 3-78) months, three (13%) patients in the cohort died. Nearly half of the patients had an ECOG performance status of 2 or 3. Most patients in the cohort (91%, n = 21) had Ann Arbor stage III-IV disease, and 88% (n = 20) had an IPI of 3 to 5. LDH levels were elevated in 83% (n = 19) of patients. Overall, 30% of patients were identified as having double-expressor lymphoma and 22% as having DHL, while two patients (9%) had THL. The origin of the lymphoma was GC B-cell-like in 15 patients (65%) and ABC-like in 8 patients (35%). Cumulative incidence of relapse at 46 months was 14% (95% CI, 5-37), while overall survival was 87% (95% CI, 64-95) and progression-free survival was 83% (95% CI, 60-93). These results showed the efficacy and an acceptable safety profile of the R-COPADM/CYVE/ASCT regimen in high-risk lymphoma, including patients with DHL.

Thiotepa, busulfan and fludarabine conditioning-regimen is a promising approach for older adult patients with acute lymphoblastic leukemia treated with allogeneic stem cell transplantation.

For acute lymphoblastic leukemia (ALL) patients, total body irradiation (TBI)- based conditioning regimens are the first choice specially in young population. However, several studies have shown an equivalence in clinical outcomes with thiotepa-based conditioning regimen. We performed a retrospective study to evaluate the outcome of adult ALL patients who received allogeneic hematopoietic stem cell transplantation (allo-HCT) with a thiotepa-busulfan-fludarabine (TBF) myeloablative conditioning regimen with reduced toxicity. Fifty-five patients received a TBF regimen. The median age of the patients was 51 years (range, 17 to 72.4). Most patients had a diagnosis of B-ALL (93%) with 7% having T-ALL. Two - and 5-year overall survival was 73.2% and 64%, respectively. At 2 years, leukemia-free survival and GVHD-free, relapse-free survival were 59.5% and 57.6%, and at 5 years, 53.4% and 51.8%, respectively. The 5-year non-relapse mortality was 15%. The day 180 cumulative incidence (CI) of grade II-IV acute GVHD and grade III-IV acute GVHD were 38.2% and 5.5%, respectively. At 2 years, the CI of chronic GVHD and extensive chronic GVHD was 16.9% and 1.9%, respectively. Our study results do suggest that using TBF as the conditioning regimen in adult ALL patients is a promising option with acceptable toxicity.

Predictive Factors of Response to Immunotherapy in Lymphomas: A Multicentre Clinical Data Warehouse Study (PRONOSTIM).

Immunotherapy (IT) is a major therapeutic strategy for lymphoma, significantly improving patient prognosis. IT remains ineffective for a significant number of patients, however, and exposes them to specific toxicities. The identification predictive factors around efficacy and toxicity would allow better targeting of patients with a higher ratio of benefit to risk. PRONOSTIM is a multicenter and retrospective study using the Clinical Data Warehouse (CDW) of the Greater Paris University Hospitals network. Adult patients with Hodgkin lymphoma or diffuse large-cell B lymphoma treated with immune checkpoint inhibitors or CAR T (Chimeric antigen receptor T) cells between 2017 and 2022 were included. Analysis of covariates influencing progression-free survival (PFS) or the occurrence of grade ≥3 toxicity was performed. In total, 249 patients were included. From this study, already known predictors for response or toxicity of CAR T cells such as age, elevated lactate dehydrogenase, and elevated C-Reactive Protein at the time of infusion were confirmed. In addition, male gender, low hemoglobin, and hypo- or hyperkalemia were demonstrated to be potential predictive factors for progression after CAR T cell therapy. These findings prove the attractiveness of CDW in generating real-world data, and show its essential contribution to identifying new predictors for decision support before starting IT.

Weak immunogenicity of SARS-CoV-2 vaccine in patients with hematologic malignancies.

This study evaluated the safety and immunogenicity of BNT162b2 vaccine in patients with hematological malignancies. Antibodies blocking spike binding to immobilized ACE-2 (NAb) correlated with anti-Spike (S) IgG d42 titers (Spearman r = 0.865, p < 0.0001), and an anti-S IgG d42 level ≥3100 UA/mL was predictive of NAb ≥ 30%, the positivity cutoff for NAb (p < 0.0001). Only 47% of the patients achieved an anti-S IgG d42 level ≥3100 UA/mL after the two BNT162b2 inocula, compared to 87% of healthy controls. In multivariable analysis, male patients, use of B-cell targeting treatment within the last 12 months prior to vaccination, and CD19+ B-cell level <120/uL, were associated with a significantly decreased probability of achieving a protective anti-S IgG level after the second BNT162b2 inoculum. Finally, using the IFN-γ ELISPOT assay, we found a significant increase in T-cell response against the S protein, with 53% of patients having an anti-S IgG-positive ELISPOT after the second BNT162b2 inoculum. There was a correlation between the anti-S ELISPOT response and IgG d42 level (Spearman r = 0.3026, p = 0.012). These findings suggest that vaccination with two BNT162b2 inocula translates into a significant increase in humoral and cellular response in patients with hematological malignancies, but only around half of the patients can likely achieve effective immune protection against COVID-19.

[Pathological analysis, an original way to study foodstuffs]. / L'anatomie pathologique, une méthode d'étude originale des denrées alimentaires.

AIM: To study the composition of foodstuffs (sausage, merguez, chipolata) on microscopic examination. MATERIAL AND METHODS: Six sausages, merguez, and chipolatas, sold in supermarkets were studied. The samples were weighed before and after dehydration to assess the water composition. Foodstuffs specimens were formalin-fixed, paraffin-embedded and analyzed on microscopic examination. Proportions of different tissues were assessed by morphometric analysis. RESULTS: Specimens contained a high proportion of water (40 to 55%). Striated muscular fibers represented from 0.7 to 15.3% for the sausages and the merguez, and from 61 to 76.5% for the chipolatas. Sausages and merguez contained from 43.3 to 49.2% of adipose tissue. All the specimens had fibrous tissue and most of them had small fragments of bone and cartilaginous tissue. Fragments of salivar glands were found in the sausages and fragments of lymphoid tissue were found in merguez. There were neither parasite nor brain tissue. Manufacturer wrote on the label the presence of "meat" with no information about the nature and the proportion of tissues in the foodstuffs specimens. Prices of the foodstuffs were globally correlated to the quantity of muscular fibers in the specimens. CONCLUSION: Pathological studies are not performed in France for the control of foodstuffs. Microscopic analysis could be interesting, as well as biochemical and bacteriological studies, in order to identify the nature and the proportion of tissues involved in the composition of the foodstuffs, to search tissues with potential risk of pathogenic agents transmission, and to search for some parasites.

A novel mouse model of acute graft-versus-host disease based on chemotherapy conditioning and G-CSF mobilized graft.

Acute graft-versus-host disease (aGVHD) is an important complication of allogeneic hematopoietic cell transplantation (HCT). The majority of aGVHD mouse models are based on radiation conditioning and bone marrow as graft, despite that most allo-HCTs performed now in clinic are based on chemotherapy conditioning and G-CSF mobilized graft. Aiming for a higher translational value, we constructed an MHC major mismatched [C57BL/6 (H-2 Kb) to BALB/c (H-2Kd)] aGVHD mouse model based on busulfan/cyclophosphomide (BU-CY) conditioning and human G-CSF mobilized splenocytes as graft. Allogeneic transplanted mice showed quick and profound donor engraftment. Moreover, there were quick onset (day +7) of typical clinical and histopathological signs of aGVHD, which gradually developed to extensive aGVHD. In addition, CD8+ T cells were the main aGVHD contributing T-cell subtype. No toxicity or GVHD signs were observed in the syngeneic setting. This clinical-relevant model offers a promising platform for future studies on aGVHD.

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.

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.