Blastic plasmacytoid dendritic cell neoplasm:Two case reports

BACKGROUND Blastic plasmacytoid dendritic cell tumor(BPDCN)is a rare and highly invasive lymphohematopoietic tumor that originates from plasmacytoid dendritic cells.BPDCN has an extremely poor prognosis.Skin lesions are usually the first manifestation of BPDCN,although the tumor may also invade the bone marrow,lymph nodes,peripheral blood,and other parts of the body,leading to several other manifestations,requiring further differentiation through skin biopsy and immunohistochemistry.CASE SUMMARY In the present paper,the cases of 2 patients diagnosed with BPDCN are discussed.The immunohistochemistry analysis of these 2 patients revealed positivity for CD4,CD56,and CD123.Currently,no standard chemotherapy regimen is available for BPDCN.Therefore,intensive therapy for acute lymphoblastic leukemia was applied as the treatment method for these 2 cases.CONCLUSION Although allogeneic bone marrow transplantation could be further effective in prolonging the median survival the ultimate prognosis was unfavorable.Future treatment modalities tailored for elderly patients will help prolong survival.

Azacitidine maintenance therapy for blastic plasmacytoid dendritic cell neoplasm allograft: A case report

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare,highly invasive malignant neoplasm.There is no universally accepted standard of care because of its rarity and the dearth of prospective research.It is still challenging for some patients to achieve persistent clinical remission or cure,despite the success of allogeneic hematopoietic stem cell transplantation(allo-HSCT),indicating that there is still a significant recurrence rate.We report a case of prevention of BPDCN allograft recurrence by azacitidine maintenance therapy and review the relevant literature.CASE SUMMARY We report a 41-year-old man with BPDCN who was admitted to hospital due to skin sclerosis for>5 mo’duration.BPDCN was diagnosed by combined clinical assessment and laboratory examinations.Following diagnosis,the patients underwent induction consolidation chemotherapy to achieve the first complete remission,followed by bridging allo-HSCT.Post-transplantation,azacitidine(75 mg/m2 for 7 d)was administered as maintenance therapy,with repeat administration every 4–6 wk and appropriate extension of the chemotherapy cycle.After 10 cycles,the patient has been disease free for 26 mo after transplantation.Regular assessments of bone marrow morphology,minimal residual disease,full donor chimerism,Epstein–Barr virus,and cytomegalovirus all yielded normal results with no abnormalities detected.CONCLUSION Azacitidine may be a safe and effective maintenance treatment for BPDCN following transplantation because there were no overt adverse events during the course of treatment.

Blastic plasmacytoid dendritic cell neoplasm in Jinhua,China:Two case reports

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare and clinically aggressive hematologic malignancy originating from the precursors of plasmacytoid dendritic cells.BPDCN often involves the skin,lymph nodes,and bone marrow,with rapid clinical progression and a poor prognosis.The BPDCN diagnosis is mainly based on the immunophenotype.CASE SUMMARY In this paper,we retrospectively analyzed 2 cases of BPDCN.Both patients were elderly males.The lesions manifested as skin masses.Morphological manifestations included diffuse and dense tumor cell infiltration of the dermis and subcutaneous tissues.Immunohistochemistry staining showed that cluster of differentiation CD4,CD56,CD43,and CD123 were positive.CONCLUSION In this paper,we retrospectively analyzed 2 cases of BPDCN.Both patients were elderly males.The lesions manifested as skin masses.Morphological manifestations included diffuse and dense tumor cell infiltration of the dermis and subcutaneous tissues.Immunohistochemistry staining showed that cluster of differentiation CD4,CD56,CD43,and CD123 were positive.

Advancing the understanding and management of blastic plasmacytoid dendritic cell neoplasm:Insights from recent case studies

We specifically discuss the mechanisms of the pathogenesis,diagnosis,and management of blastic plasmacytoid dendritic cell neoplasm(BPDCN),a rare but aggressive haematologic malignancy characterized by frequent skin manifestations and systemic dissemination.The article enriches our understanding of BPDCN through detailed case reports showing the clinical,immunophenotypic,and histopathological features that are critical for diagnosing this disease.These cases highlight the essential role of pathologists in employing advanced immunophenotyping techniques to accurately identify the disease early in its course and guide treatment decisions.Furthermore,we explore the implications of these findings for management strategies,emphasizing the use of targeted therapies such as tagraxofusp and the potential of allogeneic haematopoietic stem cell transplantation in achieving remission.The editorial underscores the importance of interdisciplinary approaches in managing BPDCN,pointing towards a future where precision medicine could significantly improve patient outcomes.

Emerging roles of plasmacytoid dendritic cell crosstalk in tumor immunity

Plasmacytoid dendritic cells(pDCs)are a pioneer cell type that produces type I interferon(IFN-I)and promotes antiviral immune responses.However,they are tolerogenic and,when recruited to the tumor microenvironment(TME),play complex roles that have long been a research focus.The interactions between p DCs and other components of the TME,whether direct or indirect,can either promote or hinder tumor development;consequently,p DCs are an intriguing target for therapeutic intervention.This review provides a comprehensive overview of p DC crosstalk in the TME,including crosstalk with various cell types,biochemical factors,and microorganisms.An in-depth understanding of p DC crosstalk in TME should facilitate the development of novel p DC-based therapeutic methods.

Blastic Plasmacytoid Dendritic Cell Neoplasm:Progress in Cell Origin,Molecular Biology,Diagnostic Criteria and Therapeutic Approaches

Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare hematological malignancy characterized by recurrent skin nodules,an aggressive clinical course with rapid involvement of hematological organs,and a poor prognosis with poor overall survival.BPDCN is derived from plasmacytoid dendritic cells(pDCs)and its pathogenesis is unclear.The tumor cells show aberrant expression of CD4,CD56,interleukin-3 receptor alpha chain(CD 123),blood dendritic cell antigen 2(BDCA 2/CD303),blood dendritic cell antigen 4(BDCA4)and transcription factor(E protein)E2-2(TCF4).The best treatment drugs are based on experience by adopting those used for either leukemia or lymphoma.Relapse with drug resistance generally occurs quickly.Stem cell transplantation after the first complete remission is recommended and tagraxofusp is the first targeted therapy.In this review,we summarize the differentiation of BPDCN from its cell origin,its connection with normal pDCs,clinical characteristics,genetic mutations and advances in treatment of BPDCN.This review provides insights into the mechanisms of and new therapeutic approaches for BPDCN.

Cilostazol inhibits plasmacytoid dendritic cell activation and antigen presentation

Background Cilostazol, an anti-platelet drug for treating coronary heart disease, has been reported to modulate immune cell functions Plasmacytoid dendritic cells （pDCs） have been found to participate in the progression of atherosclerosis mainly through interferon ct （IFN-ct） production. Whether cilostazol influences pDCs activation is still not clear. In this study, we aimed to investigate the effects of cilostazol on cell activation and antigen presentation ofpDCs in vitro in this study. Methods Peripheral blood mononuclear cells isolated by Ficoll cen- trifugation and pDCs sorted by flow cytometry were used in this study. After pretreated with cilostazol for 2 h, cells were stimulated with CpG-A, R848 or virus for 6 h or 20 h, or stimulated with CpG-B for 48 h and then co-cultured with naive T cell for five days. Cytokines in supernatant and intracellular cytokines were analyzed by ELISA or flow cytometry respectively. Results Our data indicated that cilostazol could inhibit IFN-α and tumor necrosis factor α （TNF-α） production from pDCs in a dose-dependent manner. In addition, the ability of priming na ve T cells of pDCs was also impaired by cilostazol. The inhibitory effect was not due to cell killing since the viability of pDCs did not change upon cilostazol treatment. Conclusion Cilostazol inhibits pDCs cell activation and antigen presentation in vitro, which may explain how cilostazol protects against atherosclerosis.

Blastic plasmacytoid dendritic cell neoplasm with skin and bone marrow involvement: Report of three cases

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare and highly aggressive hematopoietic malignancy.BPDCN is difficult to diagnose because of the overlap in morphologic and immunophenotypic features with various cutaneous lymphatic hematopoietic tumors.CASE SUMMARY We report on three BPDCN cases,all characterized by skin nodules and examined by histology,immunohistochemical detection,in situ hybridization for Epstein-Barr virus,and follow-up.We also review the relevant literature.All patients were positive for CD56 and negative for Epstein-Barr encoded small RNA.Two patients had bone marrow involvement.Chemotherapy is the main treatment for BPDCN,but case 1 showed bone marrow suppression and case 2 developed recurrence after chemotherapy.Case 1 survived for 7 mo,case 2 for 17 mo,and case 3 for 9 mo.CONCLUSION An accurate pathological diagnosis is a precondition for treatment,and the diagnosis of BPDCN should be based on a combination of clinical symptoms,pathological characteristics,immunophenotype,and other auxiliary examinations.It is necessary to clarify the clinicopathological features and biological behavior of BPDCN to improve its understanding by both clinicians and pathologists.Case 2 survived significantly longer than the other two cases,suggesting that the treatment received by case 2 was more effective.

The Influence of IFN-α on Blood Plasmacytoid Dendritic Cell in Chronic Myeloid Leukaemia

OBJECTIVE To study the mechanism of IFN on CML.METHODS Samples of 15 CML patients and 10 healthy controlswere studied. The flow cytometry was performed to identifycirculating pDCs. The concentration of IFN-α in serum and that inthe supernatant of peripheral blood mononuclear cells (PBMCs)cultured after stimulation with CpG ODN2216 were examinedboth in CML patients and in the healthy controlsRESULTS There was significant reduction in the numberof circulating pDCs, serum concentration of IFN-α and thecapacity of IFN-α producing PBMCs in CML patients comparedwith those in healthy control individuals (P < 0.001). After theactive treatment with IFN-α and hydroxyurea, the quantity andfunction of pDCs were increased in stabilized patients, especiallythe function of pDCs in 2 patients achieving major cytogeneticresponse (MCR). The proportion and function of pDCs and theserum levels of IFN were inversely correlated with both WBC andage of the patients with CML, and positively correlated with thestate of the illness.CONCLUSION CML patients had a reduced number anddysfunction of circulating pDCs. The active treatment with IFN inCML patients may be related to the restoration of pDCs.

The role of plasmacytoid dendritic cells(pDCs)in immunity during viral infections and beyond

Type I and III interferons(IFNs)are essential for antiviral immunity and act through two different but complimentary pathways.First,IFNs activate intracellular antimicrobial programs by triggering the upregulation of a broad repertoire of viral restriction factors.Second,IFNs activate innate and adaptive immunity.Dysregulation of IFN production can lead to severe immune system dysfunction.It is thus crucial to identify and characterize the cellular sources of IFNs,their effects,and their regulation to promote their beneficial effects and limit their detrimental effects,which can depend on the nature of the infected or diseased tissues,as we will discuss.Plasmacytoid dendritic cells(pDCs)can produce large amounts of all IFN subtypes during viral infection.pDCs are resistant to infection by many different viruses,thus inhibiting the immune evasion mechanisms of viruses that target IFN production or their downstream responses.Therefore,pDCs are considered essential for the control of viral infections and the establishment of protective immunity.A thorough bibliographical survey showed that,in most viral infections,despite being major IFN producers,pDCs are actually dispensable for host resistance,which is achieved by multiple IFN sources depending on the tissue.Moreover,primary innate and adaptive antiviral immune responses are only transiently affected in the absence of pDCs.More surprisingly,pDCs and their IFNs can be detrimental in some viral infections or autoimmune diseases.This makes the conservation of pDCs during vertebrate evolution an enigma and thus raises outstanding questions about their role not only in viral infections but also in other diseases and under physiological conditions.

Macrophage phagocytosis of SARS-CoV-2-infected cells mediates potent plasmacytoid dendritic cell activation

Early and strong interferon type I (IFN-I) responses are usually associated with mild COVID-19 disease, whereas persistent orunregulated proinflammatory cytokine responses are associated with severe disease outcomes. Previous work suggested thatmonocyte-derived macrophages (MDMs) are resistant and unresponsive to SARS-CoV-2 infection. Here, we demonstrate that uponphagocytosis of SARS-CoV-2-infected cells, MDMs are activated and secrete IL-6 and TNF. Importantly, activated MDMs in turnmediate strong activation of plasmacytoid dendritic cells (pDCs), leading to the secretion of high levels of IFN-α and TNF.Furthermore, pDC activation promoted IL-6 production by MDMs. This kind of pDC activation was dependent on direct integrinmediated cell‒cell contacts and involved stimulation of the TLR7 and STING signaling pathways. Overall, the present studydescribes a novel and potent pathway of pDC activation that is linked to the macrophage-mediated clearance of infected cells.These findings suggest that a high infection rate by SARS-CoV-2 may lead to exaggerated cytokine responses, which maycontribute to tissue damage and severe disease.

Plasmacytoid Dendritic Cells Act as the Most Competent Cell Type in Linking Antiviral Innate and Adaptive Immune Responses

Appropriate in vivo control of plasmacytoid dendritic cell （pDC） recruitment and activation is a fundamental requirement for defense against viral infection. During this process, a pivotal event that influences the outcome of viral infection is the production of high levels of type I interferon by pDCs. In particular, recent research findings showed that pDCs not only shape the nature of innate resistance, but are also responsible for the successful transition from innate to adaptive immunity for viral resistance. In addition, pDCs can differentiate into antigen presenting cells that may regulate tolerance to a given pathogen. Importantly, in a series of recent clinical studies, pDCs appeared to be defective in number and function in conditions of chronic viral diseases such as infected with HIV-1, HBV or HCV. pDC-associated clinical antiviral therapy is also emerging. This review describes research findings exatnining the functional and antiviral properties of in vivo pDC plasticity. Cellular ＆ Molecular Immunology. 2005;2（6）：411- 417.

Regulation of TLR7/9 signaling in plasmacytoid dendritic cells

Plasmacytoid dendritic cells(pDCs),also known as type I interferon(IFN)-producing cells,are specialized immune cells characterized by their extraordinary capabilities of mounting rapid and massive type I IFN response to nu-cleic acids derived from virus,bacteria or dead cells.PDCs selectively express endosomal Toll-like receptor(TLR)7 and TLR9,which sense viral RNA and DNA re-spectively.Following type I IFN and cytokine responses,pDCs differentiate into antigen presenting cells and ac-quire the ability to regulate T cell-mediated adaptive immunity.The functions of pDCs have been implicated not only in antiviral innate immunity but also in immune tolerance,inflammation and tumor microenvironments.In this review,we will focus on TLR7/9 signaling and their regulation by pDC-specific receptors.

Plasmacytoid dendritic cells promote acute kidney injury by producing interferon-α

Acute kidney injury(AKI)is a common clinical complication associated with high mortality in patients.Immune cells and cytokines have recently been described to play essential roles in AKI pathogenesis.Plasmacytoid dendritic cells(pDCs)are a unique DC subset that specializes in type Ⅰ interferon(IFN)production.Here,we showed that pDCs rapidly infiltrated the kidney in response to AKI and contributed to kidney damage by producing IFN-α.Deletion of pDCs using DTR^(BDCA2) transgenic(Tg)mice suppressed cisplatin-induced AKI,accompanied by marked reductions in proinflammatory cytokine production,immune cell infiltration and apoptosis in the kidney.In contrast,adoptive transfer of pDCs during AKI exacerbated kidney damage.We further identified IFN-α as the key factor that mediated the functions of pDCs during AKI,as IFN-α neutralization significantly attenuated kidney injury.Furthermore,IFN-α produced by pDCs directly induced the apoptosis of renal tubular epithelial cells(TECs)in vitro.In addition,our data demonstrated that apoptotic TECs induced the activation of pDCs,which was inhibited in the presence of an apoptosis inhibitor.Furthermore,similar deleterious effects of pDCs were observed in an ischemia reperfusion(IR)-induced AKI model.Clinically,increased expression of IFN-α in kidney biopsies was observed in kidney transplants with AKI.Taken together,the results of our study reveal that pDCs play a detrimental role in AKI via IFN-α.

Plasmacytoid dendritic cell deficiency in neonates enhances allergic airway inflammation via reduced production of IFN-α

Allergic asthma,a chronic inflammatory airway disease associated with type 2 cytokines,often originates in early life.Immune responses at an early age exhibit a Th2 cell bias,but the precise mechanisms remain elusive.Plasmacytoid dendritic cells(pDCs),which play a regulatory role in allergic asthma,were shown to be deficient in neonatal mice.We report here that this pDC deficiency renders neonatal mice more susceptible to severe allergic airway inflammation than adult mice in an OVA-induced experimental asthma model.Adoptive transfer of pDCs or administration of IFN-αto neonatal mice prevented the development of allergic inflammation in wild type but not in IFNAR1−/−mice.Similarly,adult mice developed more severe allergic inflammation when pDCs were depleted.The protective effects of pDCs were mediated by the pDC-/IFN-α-mediated negative regulation of the secretion of epithelial cell-derived CCL20,GM-CSF,and IL-33,which in turn impaired the recruitment of cDC2 and ILC2 cells to the airway.In asthmatic patients,the percentage of pDCs and the level of IFN-αwere lower in children than in adults.These results indicate that impairment of pDC-epithelial cell crosstalk in neonates is a susceptibility factor for the development of allergeninduced allergic airway inflammation.

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-αsecretion 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 factor7(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,Thl/Th22 polarization,and B cell differentiation towards plasmablasts.Moreover,chronically activated pDCs from SSc patients were not resistant to the selective IFN-αinhibition,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.

Mature plasmacytoid dendritic cells associated with acute myeloid leukemia show similar genetic mutations and expression profiles to leukemia cells

Introduction:Mature plasmacytoid dendritic cells(pDCs)proliferation associated with myeloid neoplasms(MPDMN)are recognized as a neoplasm related to fully differentiated pDCs.Although it has been reported for many years,the genomic landscape of MPDMN is poorly understood.Methods:We reported two patients who developed acute myeloid leukemia(French-American-British M5 subtype)coexisted with immunophenotypically mature pDCs proliferation,which fit the diagnosis of MPDMN.We sorted pDCs from myeloid blasts by flow cytometry and performed whole-exome sequencing and RNA sequencing of the two cell populations,respectively.Results:The immunophenotypes of pDCs in both patients were positive for CD123bri,HLA-DR,CD4,CD303,CD304,and negative for CD56,CD34,CD117,and TdT.The variant allele frequency of gene mutations in myeloid blasts and pDCs were similar.The expression data showed myeloid blasts clustered tightly with hematopoietic stem cells,and pDCs from patients clustered tightly with granulocyte-monocyte progenitors/common myeloid progenitor,rather than with pDCs from the GEO platform.Conclusion:Our study suggested that pDCs derived from the leukemic clone,evidenced by a shared mutation profile and similar transcriptional signatures between pDCs and concurrent myeloid blasts.

Preferential depletion of CD2^(low) plasmacytoid dendritic cells in HIV-infected subjects

Plasmacytoid dendritic cells(pDCs)are decreased in number and are functionally impaired in HIV act reasons for pDCs depletion are still unknown.It was recently reported that pDCs can be divided into two functionally distinct populations based on their CD2 expression level.To determine how the CD2high and CD2^(low) populations are affected by HIV infection,we analyzed their frequencies in the peripheral blood of HIV-infected subjects and healthy controls.We found that the CD2^(low) pDC subset was preferentially depleted in infected individuals.The frequency of CD2^(low) pDCs correlated with the CD41 T-cell count but not with the plasma viral load.This finding furthers our understanding of the causes and consequences of pDC depletion during HIV infection.

Dendritic cells in hepatitis C virus infection:Key players in the IFNL3-genotype response

Recently,single nucleotide polymorphisms,in the vicinity of the interferon lambda 3(IFNL3)gene have been identified as the strongest predictor of spontaneous and treatment induced clearance of hepatitis C virus(HCV)infection.Since then,increasing evidence has implicated the innate immune response in mediating the IFNL3 genotype effect.Dendritic cells(DCs)are key to the host immune response in HCV infection and their vital role in the IFNL3 genotype effect is emerging.Reports have identified subclasses of DCs,particularly myeloid DC2s and potentially plasmacytoid DCs as the major producers of IFNL3 in the setting of HCV infection.Given the complexities of dendritic cell biology and the conflicting current available data,this review aims to summarize what is currently known regarding the role of dendritic cells in HCV infection and to placeit into context of what is know about lambda interferons and dendritic cells in general.

Improved survival ratios correlate with myeloid dendritic cell restoration in acute-on-chronic liver failure patients receiving methylprednisolone therapy

Acute-on-chronic liver failure （ACLF） is a severe life-threatening complication. Liver transplantation is the only available therapeutic option; however, several limitations have restricted its use in patients. The use of corticosteroids as an optional therapy for ACLF has received a great deal of interest. The rationale behind its use is the possible role of the immune system in initiating and perpetuating hepatic damage. In order to assess the relationship between myeloid dendritic cells （mDCs） and the efficacy of methylprednisolone （MP） treatment for hepatitis B virus （H BV）-associated ACLF patients, we recruited 30 HBV-associated ACLF patients who had received MP treatment at lO-day intervals; 26 patients received conservative medical （CM） management as a control. The functionality of DC subsets was lower in these ACLF patients compared with healthy subjects. In addition, compared with survivors, dead/transplanted patients had lower functional mDC in both groups. Furthermore, a decreased numbers of mDC at baseline was associated with high mortality of ACLF patients. Importantly, MP treatment resulted in a significant decrease in 28-day mortality, and all MP patients exhibited an initial rapid decrease in circulating mDC numbers within 10 days of MP treatment. Subsequently, MP survivors displayed a continuous increase in mDC numbers accompanied by a decrease in total bilirubin levels by more than 30%. However, MP dead/ transplanted patients lacked these sequential responses compared with survivors. This evidence suggests strongly that the higher mDC numbers at baseline and the recovery of mDC number at the end of treatment may represent a prognostic marker for favorable response to corticosteroid treatment in ACLF patients.