Cutaneous distribution of plasmacytoid dendritic cells in lupus erythematosus. Selective tropism at the site of epithelial apoptotic damage

Recent evidences suggest a significant role of Plasmacytoid dendritic cells (PDC) role in the pathogenesis of lupus erythematosus (LE) via production of type I IFN. Taking advantage on the availability of multiple reagents (CD123, BDCA2, and CD2ap) specifically recognizing PDC on fixed tissues, we investigated the occurrence of PDC in a cohort of 74 LE patients. The large majority of LE biopsies (67/74; 90.5%) showed cutaneous infiltration of PDC. PDC were more frequently observed (96.4 vs 72.2) and numerous in cutaneous LE compared to systemic LE (SLE) and correlated with the density of the inflammatory infiltrate (r=0.40; p<0.001). PDC reduction in SLE might be related to a broader tissue distribution of this cellular population, as indicated by their occurrence in kidneys in 11 out of 24 (45.8%) cases studied. The distribution of cutaneous PDC showed two distinct patterns. More commonly, PDC were observed within perivascular inflammatory nodules in the dermis, associated with CD208+ mature DC and T-bet+ cells [D-PDC]. A second component was observed along the dermal-epithelial junction [J-PDC], in association with cytotoxic T-cells in areas of severe epithelial damage. Notably, chemerin reactivity was observed in 64% of LE biopsies on endothelial cells and in the granular layer keratinocytes. Cutaneous PDC in LE strongly produced type I IFN, as indicated by the diffuse MxA expression, and the cytotoxic molecule granzyme B.This study confirms cutaneous PDC infiltration as hallmark of LE. The topographical segregation in D-PDC and J-PDC suggests a novel view of the role of these cells in skin autoimmunity.     

PACSIN1 regulates the TLR7/9-mediated type I interferon response in plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are the professional interferon (IFN)-producing cells of the immune system. pDCs specifically express Toll-like receptor (TLR)7 and TLR9 molecules and produce massive amounts of type I IFN by sensing microbial nucleic acids via TLR7 and TLR9. Here we report that protein kinase C and casein kinase substrate in neurons (PACSIN) 1, is specifically expressed in human and mouse pDCs. Knockdown of PACSIN1 by short hairpin RNA (shRNA) in a human pDC cell line significantly inhibited the type I IFN response of the pDCs to TLR9 ligand. PACSIN1-deficient mice exhibited normal levels of conventional DCs and pDCs, demonstrating that development of pDCs was intact although PACSIN1-deficient pDCs showed reduced levels of IFN-α production in response to both cytosine guanine dinucleotide (CpG)-oligonucleotide (ODN) and virus. In contrast, the production of proinflammatory cytokines in response to those ligands was not affected in PACSIN1-deficient pDCs, suggesting that PACSIN1 represents a pDC-specific adaptor molecule that plays a specific role in the type I IFN signaling cascade.     

Type I interferon regulates pDC maturation and Ly49Q expression

Ly49Q is expressed on peripheral mouse plasmacytoid dendritic cells (pDC). Immature Ly49Q-negative pDC precursors acquire Ly49Q in the bone marrow and then migrate into the periphery. While searching for molecules that regulate pDC maturation, we found that type I interferon (IFN) inhibited Ly49Q acquisition in vitro. Infections that induce type I IFN production by cells other than pDC (a condition mimicked by poly(I:C) injection in vivo) increase the prevalence of Ly49Q(-) pDC in the bone marrow and peripheral lymphoid organs in wild-type but not IFN-alpha/beta receptor knockout BALB/c mice. Moreover, in vivo exposure to type I IFN causes some Ly49Q(-), but not Ly49Q(+), pDC to convert to conventional DC, defined as B220(-) CD11c(+) CD11b(+) cells. These data suggest that type I IFN regulates pDC development and affects their distribution in the body.     

浆细胞样树突状细胞在感染性、免疫性疾病中的研究进展

浆细胞样树突状细胞（PDC）来源于淋巴系造血干／祖细胞,能选择性的诱导免疫应答,并在一定条件下诱导免疫耐受,在抗病毒感染中起重要作用,并可能参与了某些自身免疫性疾病的发生。PDC产生的Ⅰ型IFN（IFN-α／β）在抗病毒过程中很关键,而一定条件下PDC诱导的免疫耐受与调节性T细胞的产生相关。自身免疫性疾病中持续高水平的Ⅰ型IFN提示PDC可能参与此类疾病的发病机制。     

Functional dichotomy of plasmacytoid dendritic cells: antigen-specific activation of T cells versus production of type I interferon

Human plasmacytoid dendritic cells (PDC) are believed to link innate and adaptive immunity by producing type I interferon (IFN-I) and triggering adaptive T cell-mediated immunity. However, it remains elusive to which degree both PDC functions are linked. Here we show that CMV antigen targeted to PDC using a CD303 (blood dendritic cell antigen 2, BDCA-2) mAb is rapidly endocytosed and traffics via early sorting endosomes to emerging MHC-enriched compartments. Both processes occur independently of TLR ligand stimulation. Restimulation of CMV-specific CD4(+) effector-memory T helper cells by autologous PDC and induction of IFN-I production in PDC are dependent on appropriate stimulation. Type B CpG oligonucleotide (CpG-B)-stimulated PDC efficiently process and present CMV antigen and are thus capable of stimulating CMV-specific effector-memory T helper cells. CpG-A-stimulated PDC produce large amounts of IFN-I and express programmed death receptor-1 ligand 1. CpG-A plus CpG-B-co-stimulated PDC behave like CpG-B-stimulated PDC, suggesting that antigen processing and presentation in PDC is dependent on stimulation that concurrently inhibits IFN-I production. In vivo targeting of antigens to PDC via CD303 combined with appropriate PDC stimulation may allow induction of specific T cell activation.     

干扰素调节因子5基因rs2004640多态性与系统性红斑狼疮遗传易感性的荟萃分析

目的:系统评价干扰素调节因子5基因(IRF5)rs2004640单核苷酸多态性与系统性红斑狼疮的遗传易感性在不同种族的相关关系。方法:检索Pubmed数据库、万方数据库、CNKI数据库发表的有关IRF5 rs2004640单核苷酸多态性与SLE病例对照研究的文献,应用review manager5软件,采用Mantel-Haenszel-Peto法荟萃分析IRF5 rs2004640单核苷酸多态性在不同种族中的研究。结果:荟萃分析包括亚洲、欧洲-美洲高加索人群、墨西哥印欧混血、美国黑人等不同人群的IRF5 rs2004640单核苷酸多态性14个研究,共11 725例样本。亚洲人群IRF5 rs2004640 T等位基因频率26.3%~45.5%,高加索人群IRF5rs2004640 T等位基因频率44%~56%。分别荟萃分析亚洲和高加索人群与该多态性位点关联,均提示这两种人群IRF5rs2004640 T等位基因与狼疮发病密切相关(亚洲人群OR值1.35,95%CI 1.22~1.50;高加索人群OR值1.42,95%CI 1.32~1.54;P<10-6)。荟萃分析总的结果表明IRF5 rs2004640 T等位基因与狼疮发病密切相关(OR=1.42,P<10-6)。结论:IRF5rs2004640基因多态性在不同种族人群中的荟萃分析肯定了IRF5 rs2004640 T等位基因和系统性红斑狼疮发病相关。     

Characterization of type I interferon responses in dengue and severe dengue in children in Paraguay

BackgroundInfection with dengue virus (DENV) produces a wide spectrum of clinical illness ranging from asymptomatic infection to mild febrile illness, and to severe forms of the disease. Type I interferons (IFNs) represent an initial and essential host defense response against viruses. DENV has been reported to trigger a robust type I IFN response; however, IFN-α/β profile in the progression of disease is not well characterized.Objectives and study designIn this context, we conducted a retrospective study assessing the circulating serum levels of type I IFNs and related cytokines at different phases of illness in children during the 2011 outbreak of DENV in Paraguay. Demographic, clinical, laboratory and virological data were analyzed.ResultsDuring defervescence, significantly higher levels of IFN-β, IL-6 and MIP-1β, were detected in severe vs. non-severe dengue patients. Additionally, a significant positive correlation between INF-α and viremia was detected in children with severe dengue. A significant positive correlation was also observed between IFN-β serum levels and hematocrit during the febrile phase, whereas IFN-α levels negatively correlated with white blood cells during defervescence in severe dengue patients. Furthermore, previous serologic status of patients to DENV did not influence type I IFN production.ConclusionsThe distinct type I IFN profile in children with dengue and severe dengue, as well as its association with viral load, cytokine production and laboratory manifestations indicate differences in innate and adaptive immune responses that should be investigated further in order to unveil the association of immunological and physiological pathways that underlie in DENV infection.     

The role of interferon alpha in initiation of type I diabetes in the NOD mouse

Type 1 diabetes (T1D) is an autoimmune disease in both humans and the nonobese diabetic (NOD) mouse, in which the insulin-producing-cells of the pancreatic islets are destroyed by a beta islet cell-specific T cell immune response. We recently reported that interferon (IFN)-α is an early trigger of the T1D process in NOD mice. Here, we show that extensive blockade of IFN-α action by a monoclonal antibody specific to IFN-α receptor 1 results in nearly complete prevention of T1D in NOD mice. Whether professional IFN-α producing cells, plasmacytoid dendritic cells (pDCs), are responsible for the initiation of T1D has been unclear. Here we demonstrate that depletion of pDCs in NOD mice by a specific mAb given at 15-25 days of age significantly delays the onset and decreases the incidence of T1D. These findings indicate that pDC and pDC-derived IFN-α are the prime initiators of the pathogenesis of T1D in NOD mice.     

HIV-infected cells are major inducers of plasmacytoid dendritic cell interferon production, maturation, and migration

Plasmacytoid dendritic cells (PDC), natural type-1 interferon (IFN) producing cells, could play a role in the innate anti-HIV immune response. Previous reports indicated that PDC IFN production is induced by HIV. Our results show a more robust IFN induction when purified PDC (>95%) were exposed to HIV-infected cells. This effect was not observed with non-viable cells, DNA, and RNA extracted from infected cells, and viral proteins. The response was blocked by anti-CD4 and neutralizing anti-gp120 antibodies as well as soluble CD4. IFN induction by HIV-infected cells was also prevented by low-dose chloroquine, which inhibits endosomal acidification. PDC IFN release resulted in reduced HIV production by infected CD4+ cells, supporting an anti-HIV activity of PDC. Stimulated CD4+ cells induced PDC activation and maturation; markers for PDC migration (CCR7) were enhanced by HIV-infected CD4+ cells only. This latter finding could explain the decline in circulating PDC in HIV-infected individuals.     

Natural mannosylation of HIV-1 gp120 imposes no immunoregulatory effects in primary human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) play a vital role in activation of anti-HIV-1 immunity, and suppression of pDCs might mitigate immune responses against HIV-1. HIV-1 gp120 high-mannose has been attributed immunosuppressive roles in human myeloid DCs, but no receptors for high-mannose have so far been reported on human pDCs. Here we show that upon activation with HIV-1 or by a synthetic compound triggering the same receptor in human pDCs as single-stranded RNA, human pDCs upregulate the mannose receptor (MR, CD206). To examine the functional outcome of this upregulation, inactivated intact or viable HIV-1 particles with various degrees of mannosylation were cultured with pDCs. Activation of pDCs was determined by assaying secretion of IFN-alpha, viability, and upregulation of several pDC-activation markers: CD40, CD86, HLA-DR, CCR7, and PD-L1. The level of activation negatively correlated with degree of mannosylation, however, subsequent reduction in the original mannosylation level had no effect on the pDC phenotype. Furthermore, two of the infectious HIV-1 strains induced profound necrosis in pDCs, also in a mannose-independent manner. We therefore conclude that natural mannosylation of HIV-1 is not involved in HIV-1-mediated immune suppression of pDCs.     

造血干细胞移植治疗系统性红斑狼疮的进展

系统性红斑狼疮是一种病因未明的自身免疫性疾病,基本上由自身抗体和免疫复合物介导致病.随着医学在基因水平上不断发展,对于重症SLE不能耐受传统疗法,HSCT目前已是公认的潜在治疗手段之一.从报道HSCT治疗严重AID至今,大约有20个国家的700个患者接受了临床Ⅰ/Ⅱ试验.研究认为,大剂量免疫抑制和移植后免疫重建可能是使SLE缓解的机制.经过10年的临床试验,国内对HSCT治疗手段不断成熟,以北京协和医院为首.虽有明显改善SLE病情,但随诊时期不长,仍存在着许多需要进一步解决的问题,HSCT给予那些难治的其他疗法无效的患者提供了"补救疗法",是否更有效,仍需要进一步进行随机化控制实验.     

Severe herpes virus (HSV-2) infection in two patients with myelodysplasia and undetectable NK cells and plasmacytoid dendritic cells in the blood

BACKGROUND: How the immune system contains herpes simplex virus (HSV) infections is partly understood. T cells from infected persons proliferate in response to HSV antigens in vitro and may control local relapse rather than primary infection. NK cells have been involved in the control of experimental infections. A potentially important, as yet unexplored, population of interest might be the plasmacytoid dendritic cells (PDC), which contrary to monocytes, produce very high amounts of the major antiviral molecules, type-I interferon (IFN) following interaction with HSV. OBJECTIVES: Measure type-I IFN production, PDC, and NK cells in patients with unusually severe HSV infections. STUDY DESIGN: Two female patients of 33- and 50-year-old, respectively were referred because of severe disseminated HSV2 infection and myelodysplastic marrow. One patient had leukaemia and a primary HSV2 infection whereas the other had systemic lupus erythematosus (SLE) and a chronic HSV2 infection. The following studies were performed at various time points over 18 months: analysis of the lymphocytes and PDC subsets phenotype, lymphocyte proliferation assays to recall antigens; generation of NK cells in cultures, and production of type-I IFN in serum and by HSV-infected and by sendai virus (SV)-infected blood cells. RESULTS AND CONCLUSIONS: PDC and NK cells were undetectable in the blood of both patients and NK cells could not be generated in culture at the time of ongoing infection. PBMC failed to produce IFN after infection with HSV contrasting with a normal T cell proliferation to HSV antigens in patient 1. Our observation suggests that innate immunity, through NK cells and PDC may control HSV infections, and together with IFN-producing capacity, should be investigated in patients with unusually severe HSV infections.     

The tyrosine kinase inhibitor dasatinib suppresses cytokine production by plasmacytoid dendritic cells by targeting endosomal transport of CpG DNA

Plasmacytoid dendritic cells (pDCs) produce a vast amount of interferon (IFN)‐α in response to nucleic acids from viruses and damaged self‐cells through Toll‐like receptor (TLR)7 and TLR9. Pharmaceutical agents that suppress IFN‐α production by pDCs are instrumental in elucidating the mechanisms behind IFN‐α production, and in developing novel therapies for inflammatory disorders that involve pDCs. Here, we show that a tyrosine kinase inhibitor for chronic myeloid leukemia with multiple targets, dasatinib, strongly suppresses production of IFN‐α and proinflammatory cytokines by human pDCs stimulated with multimeric CpG oligodeoxynucleotides (CpG‐A) without reducing viability. In contrast, other tyrosine kinase inhibitors, imatinib, and nilotinib, did not suppress the cytokine production at clinically relevant concentrations. Inhibitors of SRC family kinases (SFKs), which are prominent targets of dasatinib, also suppressed the cytokine production. Notably, however, dasatinib, but not SFK inhibitors, abrogated prolonged localization of CpG‐A in early endosomes, which is a critical step for pDCs to produce a large amount of IFN‐α. This study suggests that dasatinib suppresses IFN‐α production by pDCs by inhibiting SFK‐dependent pathways and SFK‐independent endosomal retention of CpG DNA. Kinases controlling the distinctive endosomal trafficking in pDCs may be exploited as targets to develop novel therapies for pDC‐related inflammatory disorders.     

The C protein of measles virus inhibits the type I interferon response

Type I interferons (IFNalpha/beta) are an important part of innate immunity to viral infections because they induce an antiviral response and limit viral replication until the adaptive response clears the infection. Since the nonstructural proteins of several paramyxoviruses inhibit the IFNalpha/beta response, we chose to explore the role of the C protein of measles virus (MV) in such inhibition. Previous studies have suggested that the MV C protein may serve as a virulence factor, but its role in the pathogenesis of MV remains undefined. In the present study, a recombinant MV strain that does not express the C protein (MV C-) and its parental strain (Ed Tag) were used. Growth of MV C- was restricted in human peripheral blood mononuclear cells and HeLa cells, but in the presence of neutralizing antibodies to IFNalpha/beta, MV C- produced titers that were equivalent to those of Ed Tag. In addition, expression of the MV C protein from plasmid DNA inhibited the production of an IFNalpha/beta responsive reporter gene and, to a lesser extent, inhibited an IFNgamma responsive reporter gene. The ability of the MV C protein to suppress the IFNalpha/beta response was confirmed using a biologic assay. After IFNbeta stimulation, HeLa cells infected with Ed Tag produced five-fold less IFNalpha/beta than cells infected with MV C-. While the mechanism of inhibition remains unclear, these data suggest that the MV C protein plays an important role in the pathogenesis of MV by inhibiting IFNalpha/beta signaling.     

The Role of Plasmacytoid and Myeloid Dendritic Cells in Induction of Asthma in a Mouse Model and the Effect of a TLR9 Agonist on Dendritic Cells

Purpose

To determine the role of plasmacytoid dendritic cells (pDC) and myeloid dendritic cells (mDC) in priming effector T cells to induce allergy, and to evaluate the effect of immunostimulatory sequences (ISS, TLR9 agonist) on dendritic cells.

Methods

Cultured mDC and pDC with/without ISS were injected intratracheally into sensitized Balb/C mice. Mice were sacrificed, and then pulmonary function tests, bronchoalveolar lavage (BAL), cell counts, and cytokine levels were evaluated. Migration of dendritic cells was also evaluated after ISS administration.

Results

In mice injected with mDC, airway hyperresponsiveness, eosinophil counts, and Th2 cytokine levels in BAL increased with increasing numbers of mDC injected. However, in mice injected with pDC, none of these changed, suggesting poor priming of T cells by pDC. In addition, mDC pulsed with ISS inhibited asthmatic reactions, and ISS administration inhibited migration of DC to the lung.

Conclusions

We suggest that pDC played a limited role in priming T cells in this asthma model and that mDC played a major role in inducing asthma. In addition, ISS inhibited migration of DC to the lung.     

B cells in glomerulonephritis: focus on lupus nephritis

The production of pathogenic antibody has been traditionally viewed as the principle contribution of B cells to the pathogenesis of immune-mediated glomerulonephritis. However, it is increasingly appreciated that B cells play a much broader role in such diseases, functioning as antigen-presenting cells, regulators of T cells, dendritic cells, and macrophages and orchestrators of local lymphatic expansion. In this review, we provide an overview of basic B cell biology and consider the evidence implicating B cells in one of the archetypal immune-mediated glomerulonephritides, lupus nephritis.