Distinct DC Subsets Research Articles

Profound deficiencies in mature blood and bone marrow progenitor dendritic cells in Chronic Lymphocyticcytic Leukemia patients.

Chronic lymphocytic leukemia (CLL) patients are immunocompromised and highly vulnerable to serious recurrent infections. Conventional dendritic cells (cDCs) and plasmacytoid DCs (pDCs) are principal sensors of infection and are essential in orchestrating innate and adaptive immune responses to resolve infection. This study identified significant deficiencies in six functionally distinct DC subsets in blood of untreated CLL (UT-CLL) patients and selective normalization of pDCs in response to acalabrutinib (a Bruton tyrosine kinase inhibitor) therapy. DCs are continuously replenished from hematopoiesis in bone marrow (BM). Four BM developmental intermediates that give rise to cDCs and pDCs were examined and significant reductions of these were identified in UT-CLL patients supporting a precursor/progeny relationship. The deficiencies in blood DCs and BM DC progenitors were significantly associated with alterations in the Flt3/FL signaling pathway critical to DC development and function. Regarding clinical parameter, cDC subset deficiencies are associated with adverse prognostic indicators of disease progression, including IGHV mutation, CD49d, CD38, and ZAP-70 status. Importantly, UT-CLL patients with shared DC subset deficiencies had shorter time-to-first treatment (TTFT), uncovering a profound alteration in innate immunity with the potential to instruct therapeutic decision-making.

Expression of leukotriene B4 receptor 1 defines functionally distinct DCs that control allergic skin inflammation

Leukotriene B4 (LTB4) receptor 1 (BLT1) is a chemotactic G protein-coupled receptor expressed by leukocytes, such as granulocytes, macrophages, and activated T cells. Although there is growing evidence that BLT1 plays crucial roles in immune responses, its role in dendritic cells remains largely unknown. Here, we identified novel DC subsets defined by the expression of BLT1, namely, BLT1hi and BLT1lo DCs. We also found that BLT1hi and BLT1lo DCs differentially migrated toward LTB4 and CCL21, a lymph node-homing chemoattractant, respectively. By generating LTB4-producing enzyme LTA4H knockout mice and CD11c promoter-driven Cre recombinase-expressing BLT1 conditional knockout (BLT1 cKO) mice, we showed that the migration of BLT1hi DCs exacerbated allergic contact dermatitis. Comprehensive transcriptome analysis revealed that BLT1hi DCs preferentially induced Th1 differentiation by upregulating IL-12p35 expression, whereas BLT1lo DCs accelerated T cell proliferation by producing IL-2. Collectively, the data reveal an unexpected role for BLT1 as a novel DC subset marker and provide novel insights into the role of the LTB4-BLT1 axis in the spatiotemporal regulation of distinct DC subsets.

P234 Characterisation of human synovial tissue dendritic cells in rheumatoid arthritis patients

Abstract Background Dendritic cells (DCs) direct immune responses against pathogens while maintaining tolerance to self-antigens. However, their aberrant activation can lead to autoimmunity and inflammation. DCs consist of two subtypes: plasmacytoid and myeloid DCs. Recently, single-cell sequencing has revealed complex heterogeneity within myeloid DCs. These cells can be divided into CD141pos (DC1), DC2 defined as CD1highCD163neg and DC3 defined as CD1clowCD163high. In addition, a population of CD1cnegCD141negCD16pos (DC4), which share some gene expression with CD16pos monocytes, has been identified. To date, most studies of RA investigated DC precursors in circulation or synovial fluid (SF). However, DCs perform their functions within lymphoid or peripheral tissue. Therefore, in this study, we sought to characterise myeloid DC subsets in synovial tissue (ST) with the prospect of better understanding their role in driving autoimmunity in RA. Methods We developed a flow sorting strategy to characterise the phenotype of distinct myeloid DC subsets in multiple biological compartments (PB, SF, and ST). Ultrasound-guided ST biopsies (RA n = 9; Psoriatic arthritis n = 3 with active disease) were digested with liberase prior to analysis. PB DCs (RA n = 19, Psoriatic arthritis n = 16, healthy donors n = 12), and SF DC (n = 3) were used as comparators. ST, SF and PB DCs were sorted then microRNA, pro-inflammatory and regulatory cytokine expression analysed by amplified qPCR. To evaluate the role of miR-155 in RA CD1cpos DC activation, CD1cpos cells were computationally sub-setted from a scRNAseq synovial dataset comparing synovial tissues of healthy individuals (n = 4) with patients with active RA (n = 7) and those in sustained clinical and ultrasound remission (n = 7). To elucidate the role of miR-155, CD1cpos DC from RA patients (n = 10) were sorted then transfected with miR-155 mimic or control mimic and the cytokines expression and produced were evaluated using quantitative RT-PCR and Luminex, respectively. Results Our data revealed that whilst all myeloid DCs subsets can be present in inflamed RA synovium they occur with variable frequencies. CD1cpos (DC2/3) being the most abundant, followed by CD16pos DCs (DC4), whilst CD141pos DCs (DC1) occur in low numbers or are absent. CD1cpos DC sorted from RA ST express high levels of epigenetic regulators of inflammatory response miR-155, IL-6, TNF-a and IL-23 as compared to circulating cells.Unsupervised clustering of synovial CD1c cells identified 4 separate clusters including a distinctive miR155 positive CD1c cluster in RA patients. These cells showed significantly higher expression of pro-inflammatory cytokines and co-stimulatory molecules compared to other synovial CD1c clusters. Overexpression of miR-155 in CD1cpos leads to increased production of TNF-a and IL-23. Conclusion Our data show that miR-155 is strongly implicated as an epigenetic regulator of the pro-inflammatory synovial CD1cpos DCs sub-cluster and contributes to exacerbating RA. Disclosures A. Elmesmari None. L. MacDonald None. D. Vaughan None. B. Tolusso None. L. Bui None. M. Gigante None. F. Federico None. G. Ferraccioli None. E. Gremese None. I. B McInnes None. S. Alivernini None. M. Kurowska-Stolarska None.

Human Dendritic Cell Subsets Undergo Distinct Metabolic Reprogramming for Immune Response.

Toll-like receptor (TLR) agonists induce metabolic reprogramming, which is required for immune activation. We have investigated mechanisms that regulate metabolic adaptation upon TLR-stimulation in human blood DC subsets, CD1c+ myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). We show that TLR-stimulation changes expression of genes regulating oxidative phosphorylation (OXPHOS) and glutamine metabolism in pDC. TLR-stimulation increases mitochondrial content and intracellular glutamine in an autophagy-dependent manner in pDC. TLR-induced glutaminolysis fuels OXPHOS in pDCs. Notably, inhibition of glutaminolysis and OXPHOS prevents pDC activation. Conversely, TLR-stimulation reduces mitochondrial content, OXPHOS activity and induces glycolysis in CD1c+ mDC. Inhibition of mitochondrial fragmentation or promotion of mitochondrial fusion impairs TLR-stimulation induced glycolysis and activation of CD1c+ mDCs. TLR-stimulation triggers BNIP3-dependent mitophagy, which regulates transcriptional activity of AMPKα1. BNIP3-dependent mitophagy is required for induction of glycolysis and activation of CD1c+ mDCs. Our findings reveal that TLR stimulation differentially regulates mitochondrial dynamics in distinct human DC subsets, which contributes to their activation.

Distinct DC subsets regulate adaptive Th1 and 2 responses during Trichuris muris infection.

Low- and high-dose infections with the murine large intestinal nematode Trichuris muris are associated with induction of adaptive Th1 and Th2 responses, respectively, in mesenteric lymph nodes (MLN). Classical dendritic cells (cDC) accumulate in the large intestinal mucosa and MLN upon T. muris infection, yet their role in driving adaptive responses to infection remains largely unknown. We performed low- and high-dose T. muris infections of mice deficient in defined cDC subsets to investigate their role in induction of adaptive immune responses. Mice lacking IRF4-dependent cDC failed to clear a high-dose infection and displayed impaired Th2 responses. Conversely, mice lacking IRF8-dependent cDC cleared a low-dose infection and displayed an impaired Th1 response while increased production of Th2 cytokines. Finally, mice lacking both IRF4- and IRF8-dependent cDC were able to generate a Th2 response and clear a low-dose infection. Collectively, these results suggest that IRF4- and IRF8-dependent cDC act antagonistically during T. muris infection, and demonstrate that intestinal Th2 responses can be generated towards T. muris in the absence of IRF4-dependent cDC.

Krüppel-ling of IRF4-Dependent DCs into Two Functionally Distinct DC Subsets

IRF4-dependent DCs have been associated with induction of both Th1 and Th17 cells. In this issue of Immunity, Tussiwand et al. (2015) demonstrate that a dependence on KLF4 identifies a subset of IRF4-dependent DC that preferentially promotes Th2 cell differentiation.

134: TLR2 and TLR4 differentially regulate DC to stimulate T cell cytokines in response to mycoplasma superantigen

Mycoplasma arthritidis induces arthritis, toxic shock and skin necrosis in mice. M. arthritidis mitogen (MAM), a potent superantigen (SAg) secreted by M. arthritidis , contributes to some of these symptoms in certain mouse strains. We previously demonstrated that C3H mouse strains differing in expression of TLR4, differ in immune reactivity to MAM due to differential engagement of TLR2 and TLR4. Herein, we demonstrated that in TLR4-defect C3H/HeJ (TLR2+/4−) mice, following injection of MAM SAg, the splenic DCs were activated to express significantly higher B7-1 + CD8a + surface markers than expressed in wild-type mice, and produced remarkably elevated IL-1b, IL-12p40, IFNg, and TNFa. In contrast, in wild-type C3H/HeSnJ (TLR2+/4+) mice, the interaction of MAM with both TLR4 and TLR2 led to reduction of the B7-1 + CD8a + DC subset that led to the down-regulated TNFa and IFNg, but up-regulated IL-6, IL-10 and IL-17. Interestingly, in mice injected with live M. arthritidis , injections of anti-B7-1 antibody to C3H/HeSnJ but not C3H/HeJ greatly enhanced arthritis severity that is now found to be associated to the elevation of IL-6, TGFb, IL-17 and IL-23 in sera or in the culture supernatants of splenic T cells. Thus the results suggest that TLR2 and/or TLR4 differentially control distinct DC subsets to influence Th17 differentiation in response to MAM superantigen. DC function that is regulated as the consequence of the cross-talk of discrete TLRs, B7-1 and CD8a molecules in response to MAM SAg might largely influence the outcome of subsequent adaptive immune responses in murine inflammatory diseases caused by M. arthritidis .

Transcriptional and functional conservation between human Langerhans cells and mouse thymic DCs (P5067)

Abstract The characterization of human DC subsets is essential for the design of new vaccines and for better translation of mouse immunological data to the clinic. Previously, we showed that human epidermal Langerhans cells (LCs) were highly efficient at priming effector CD8+ T cell responses. However, the ability of mouse LCs to cross-present antigens and drive potent CTL responses is controversial. We used expression profiling to find the human LC equivalent in the mouse. Our studies suggest that the mouse equivalent to the human LC are the two mouse thymic DC subsets. Our studies also reveal a distinct genetic signature of over 25 genes, that could identify and predict which DC subsets can cross-present. The cross-presentation signature was present in the human blood CD141+ DCs and correctly identified the ability of other distinct human and mouse DC subsets to cross present. We confirmed these predictions with the functional ability of DCs to efficiently induce antigen-specific effector CD8+ T cells. Our studies may help bridge differences between mouse and human DCs and facilitate the application of these data to the clinic.

E‐cadherin interactions are required for Langerhans cell differentiation

Human skin contains the following two distinct DC subsets: (i) Langerhans cells (LCs), expressing Langerin but not DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), are predominantly localized in the epidermis; and (ii) dermal DCs, expressing DC-SIGN but not Langerin, are observed mainly in the dermis. It is not known whether localization in the epidermis provides cues for LC differentiation. Here, we show that E-cadherin expressed by epidermal keratinocytes (KCs) is crucial for differentiation of LCs. Monocytes differentiated into LC-like cells in presence of IL-4, GM-CSF, and TGF-β1. However, these LC-like cells expressed not only Langerin but also DC-SIGN. Notably, co-culturing of these LC-like cells with KCs expressing E-cadherin or recombinant E-cadherin strongly decreased expression of DC-SIGN and further induced a phenotype similar to purified epidermal LCs. Moreover, pretreatment of LC-like cells with anti-E-cadherin-specific antibody completely abolished their Langerin expression, indicating the requirement of E-cadherin–E-cadherin interactions for the differentiation into Langerin+ cells. These findings suggest that E-cadherin expressed by KCs provide environmental cues that induce differentiation of LCs in the epidermis.

Differential expression of co-signal molecules and migratory properties in four distinct subsets of migratory dendritic cells from the oral mucosa

Variations in co-signal ligand expression and cytokine production greatly influence the antigen-presenting properties of migrating DCs in regional lymph nodes (RLNs). Here we investigated DCs migrating from the oral mucosa using CD326 and CD103 antigens for discriminate CD207 + Langerhans cells (LCs) from CD207 + submucosal DCs (SMDCs). Similar to DCs migrating from the skin, we identified four distinct oral mucosal DC (OMDC) subsets, CD11c hiCD207 −CD103 −CD326 intCD11b hi (F1; resident CD11b hi SMDCs), CD11c int/loCD207 -CD103 -CD326 loCD11b int/hi (F2; newly recruited blood-derived SMDCs), CD11c int/loCD207 +CD103 +CD326 int/hiCD11b lo (CD103 + F3; resident CD207 + SMDCs), and CD11c int/loCD207 +CD103 -CD326 int/hiCD11b lo (CD103 - F3; resident LCs). F1 DCs migrated rapidly after fluorescein isothiocyanate (FITC) painting and expressed notably high levels of CD86, CD273, and CD274 at an earlier time point. In contrast, CD103 − LCs expressing the highest levels of the epithelial cell adhesion molecule CD326 accounted for a minor subset at the earlier time point, but increased slowly with CD103 +CD207 + SMDCs. However, their expression of CD86, CD273, and CD274 was very limited. The delayed migration and limited induction of co-signal ligands suggest that roles of OMLCs are distinct from those of the other three DC subsets. The identification of distinct subsets of OMDCs in RLNs may benefit efforts to determine the functional specialization of each subset in T cell responses against orally administrated antigens.

Phenotypic localization of distinct DC subsets in mouse Peyer Patch

Peyer's patch have been extensively studied as a major inductive site for mucosal immunity within the small intestine. The intestinal mucosa contains numerous dendritic cells, which induce either protective immunity to infectious agents or tolerance to innocuous antigens, including food and commensal bacteria. Although during the past few years, several subsets of human mucosal dendritic cells have been described, a precise characterization of the different mouse mucosal dendritic cells subpopulations remains to be achieved with regard to their phenotype and localization in Peyer's patch. In this report, we have investigated by immunofluorescence on cryosection and by flow cytometry, the phenotype and the localization of dendritic cells into Peyer's patch of C57Bl/6 mouse intestine using dendritic cells markers. Positive and double staining for CD11c and BDCA-2, pDC/IPC, DC-LAMP, DC-SIGN, TLR8 and Langerin have been observed revealing new mouse intestinal DC subsets. This study provides new insight in the understanding of mucosal immune responses induced by natural processes as infections but also new perspectives for the evaluation of oral vaccines.

CD207+ CD103+ dermal dendritic cells cross-present keratinocyte-derived antigens irrespective of the presence of Langerhans cells

Recent studies have challenged the view that Langerhans cells (LCs) constitute the exclusive antigen-presenting cells of the skin and suggest that the dermal dendritic cell (DDC) network is exceedingly complex. Using knockin mice to track and ablate DCs expressing langerin (CD207), we discovered that the dermis contains five distinct DC subsets and identified their migratory counterparts in draining lymph nodes. Based on this refined classification, we demonstrated that the quantitatively minor CD207+ CD103+ DDC subset is endowed with the unique capability of cross-presenting antigens expressed by keratinocytes irrespective of the presence of LCs. We further showed that Y-Ae, an antibody that is widely used to monitor the formation of complexes involving I-Ab molecules and a peptide derived from the I-E α chain, recognizes mature skin DCs that express I-Ab molecules in the absence of I-E α. Knowledge of this extra reactivity is important because it could be, and already has been, mistakenly interpreted to support the view that antigen transfer can occur between LCs and DDCs. Collectively, these data revisit the transfer of antigen that occurs between keratinocytes and the five distinguishable skin DC subsets and stress the high degree of functional specialization that exists among them.

Cutting Edge: Limited Specialization of Dendritic Cell Subsets for MHC Class II-Associated Presentation of Viral Particles

Dendritic cells (DCs) are the most important APC. It was recently reported that there is a dichotomy for Ag presentation by DC subsets; exogenous Ags reach the MHC class I pathway, but not the MHC class II pathway, in CD8(+) DCs, whereas CD8(-) DCs only process Ags for the MHC class II pathway. In this study, we used virus-like particles (VLPs) to show that CD8(+) and CD8(-) DCs efficiently capture and process VLPs for presentation in association with MHC class II in vivo. In contrast, CD8(+) DCs, but not CD8(-) DCs, cross presented VLP-derived peptides. This pattern was changed in an FcgammaR-dependent fashion in the presence of VLP-specific Abs, because under those conditions both DC subsets failed to efficiently cross present. Thus, the presentation of viral particles to CD4(+) T cells is not restricted to distinct DC subsets, whereas the presentation of viral particles to CD8(+) T cells is limited to CD8(+) DCs.

Kidney dendritic cell activation is required for progression of renal disease in a mouse model of glomerular injury

The progression of kidney disease to renal failure correlates with infiltration of mononuclear immune cells into the tubulointerstitium. These infiltrates contain macrophages, DCs, and T cells, but the role of each cell type in disease progression is unclear. To investigate the underlying immune mechanisms, we generated transgenic mice that selectively expressed the model antigens ovalbumin and hen egg lysozyme in glomerular podocytes (NOH mice). Coinjection of ovalbumin-specific transgenic CD8+ CTLs and CD4+ Th cells into NOH mice resulted in periglomerular mononuclear infiltrates and inflammation of parietal epithelial cells, similar to lesions frequently observed in human chronic glomerulonephritis. Repetitive T cell injections aggravated infiltration and caused progression to structural and functional kidney damage after 4 weeks. Mechanistic analysis revealed that DCs in renal lymph nodes constitutively cross-presented ovalbumin and activated CTLs. These CTLs released further ovalbumin for CTL activation in the lymph nodes and for simultaneous presentation to Th cells by distinct DC subsets residing in the kidney tubulointerstitium. Crosstalk between tubulointerstitial DCs and Th cells resulted in intrarenal cytokine and chemokine production and in recruitment of more CTLs, monocyte-derived DCs, and macrophages. The importance of DCs was established by the fact that DC depletion rapidly resolved established kidney immunopathology. These findings demonstrate that glomerular antigen-specific CTLs and Th cells can jointly induce renal immunopathology and identify kidney DCs as a mechanistic link between glomerular injury and the progression of kidney disease.

Murine epidermal Langerhans cells and langerin-expressing dermal dendritic cells are unrelated and exhibit distinct functions

A new langerin(+) DC subset has recently been identified in murine dermis (langerin(+) dDC), but the lineage and functional relationships between these cells and langerin(+) epidermal Langerhans cells (LC) are incompletely characterized. Selective expression of the cell adhesion molecule EpCAM by LC allowed viable LC to be easily distinguished from langerin(+) dDC in skin and lymphoid tissue and ex vivo as well. Differential expression of EpCAM and langerin revealed the presence of at least 3 distinct skin DC subsets. We determined that LC and langerin(+) dDC exhibit different migratory capabilities in vitro and repopulate distinct anatomic compartments in skin at different rates after conditional depletion in vivo. Langerin(+) dDC, in contrast to LC, did not require TGFbeta1 for development. Carefully timed gene gun immunization studies designed to take advantage of the distinct repopulation kinetics of langerin(+) dDC and LC revealed that langerin(+) dDC were required for optimal production of beta-galactosidase-specific IgG2a/c and IgG2b in the acute phase. In contrast, immunization via LC-deficient skin resulted in persistent and strikingly reduced IgG1 and enhanced IgG2a Ab production. Our data support the concepts that LC and langerin(+) dDC represent distinct DC subsets that have specialized functions and that LC are important immunoregulatory cells. The presence of at least 3 functionally distinct skin DC subsets may have particular relevance for vaccines that are administered epicutaneously.

Provision of antifungal immunity and concomitant alloantigen tolerization by conditioned dendritic cells in experimental hematopoietic transplantation

FoxP3 + regulatory T (Treg) cells are important mediators of peripheral tolerance, and deficiency of this population is associated with autoimmune inflammation and onset of acute lethal graft-vs.-host disease in transplantation. Type I IFN-producing plasmacytoid dendritic cells (pDC) are implicated in the induction and maintenance of tolerance and contribute to engraftment facilitation and prevention of graft-vs.-host disease after allogeneic hematopoietic stem cells transplantation (HSCT). Because host DC function is impaired during the immediate period post-transplant, the administration of donor DC may be useful for the educational program of recovering T cells. Distinct DC subsets could be derived from bone marrow (murine) or peripheral CD14 + cell (human) cultures in the presence of either GM-CSF/IL-4 (myeloid DC) or FLT3-ligand (mainly pDC). The ability of either DC subset to induce Th1/Treg cell priming against Aspergillus fumigatus as well as the relative contribution of murine DC subsets to antifungal priming upon adoptive transfer in hematopoietic transplanted mice with aspergillosis is not known. We found specialization and complementarity in priming and tolerization by the different DC subsets, with FL-DC fulfilling the requirement for (i) Th1/Treg antifungal priming; ii) tolerization toward alloantigens and (iii) diversion from alloantigen-specific to antigen-specific T cell responses in the presence of donor T lymphocytes. Interestingly, thymosin α1 (Tα1), known to modulate human pDC functions trough TLR9, affects mobilization and tolerization of pDC by activating the indoleamine 2,3-dioxygenase-dependent pathway, and this resulted in Treg development and tolerization. Thus, transplantation tolerance and concomitant pathogen clearance could be achieved through the therapeutic induction of antigen-specific Treg cells via instructive immunotherapy with pathogen- or TLR-conditioned donor DC.

Vaccination with plasmacytoid dendritic cells induces protection against infection with Leishmania major in mice

DC-based vaccination against Leishmania major induces a parasite-specific Th1 response and long-lasting protective immunity in susceptible mice. Since distinct DC subsets have been proposed to direct the predominant development of either Th1 or Th2 cells, we analyzed the capability of plasmacytoid DC (pDC) to induce protection and elicit a Th1 response against L. major. Pulsing with L. major lysate induced the activation and maturation of semi-mature murine pDC that had been isolated from the spleen, as indicated by up-regulation of the co-stimulatory molecules CD86 and CD80, but did not enhance the level of IFN-alpha secretion by pDC. Vaccination of susceptible mice with L. major lysate-pulsed pDC induced highly effective T cell-mediated immunity against subsequent infection with L. major parasites. Surprisingly, the protection was not accompanied by a polarized Th1 cytokine profile. Co-activation of pDC with CpG-containing oligodeoxynucleotides, which has been shown to be critical for activating the protective potential of myeloid DC, was not required for the protective effect of L. major antigen-pulsed pDC. These findings demonstrate that antigen-loaded pDC are able to induce T cell-mediated protection against a parasite disease and that experimental leishmaniasis is a suitable model to elucidate the mechanisms underlying DC-based vaccination against infections.

Immunomodulatory Dendritic Cells Inhibit Th1 Responses and Arthritis via Different Mechanisms

Dendritic cells (DCs) are professional APCs which have the unique ability to present both foreign and self-Ags to T cells and steer the outcome of immune responses. Because of these characteristics, DCs are attractive vehicles for the delivery of therapeutic vaccines. Fully matured DCs are relatively well-defined and even used in clinical trials in cancer. DCs also have the potential to influence the outcome of autoimmunity by modulating the underlying autoimmune response. To gain a better appreciation of the abilities and mechanisms by which immunomodulatory DCs influence the outcome of T cell responses, we studied several immunomodulatory DCs (TNF-, IL-10-, or dexamethasone-stimulated bone marrow-derived DCs) side by side for their ability to modulate T cell responses and autoimmune diseases. Our data show that these differentially modulated DCs display a different composition of molecules involved in T cell activation. Although, all DC subsets analyzed were able to inhibit the induction of collagen-induced arthritis, the modulation of the underlying immune response was different. Vaccination with TNF- or IL-10-modulated DCs altered the Th1/Th2 balance as evidenced by the induction of IL-5- and IL-10-secreting T cells and the concomitant reduction of the IgG2a-IgG1 ratio against the immunizing Ag. In contrast, DCs modulated with dexamethasone did not affect the ratio of IL-5-producing vs IFN-gamma-producing T cells and tended to affect the Ab response in a nonspecific manner. These data indicate that distinct mechanisms can be used by distinct DC subsets to change the outcome of autoimmunity.

Distinct subsets of dendritic cells drive tolerance in two models of CD4 T cell mediated autoimmunity (129.14)

Abstract Dendritic cells (DCs) are professional antigen presenting cells that are capable of presenting both self and foreign antigens to T cells thereby inducing either tolerance or immunity respectively. What is still not clear is whether T cell tolerance requires a specific subset or any population of DCs can drive tolerance. To address this question different subsets of DCs were tested for suppression of autoimmunity in two major animal models- type I diabetes (T1D) and experimental allergic encephalomyelitis (EAE). There are 3 major subsets of DCs in spleen- CD8α+, CD8α−CD4+ and CD8α−CD4−. In this study we investigated the ability of these subsets to induce tolerance in TID and EAE. Indeed the CD8α−CD4− DC subset mediated protection against diabetes in non-obese diabetic (NOD) mice. In fact, mice had reduced destructive infiltration within the islets and the antigen-specific lymphocytes showed reduced proliferation and an increase in IFNγ and IL-10 response. Surprisingly, in EAE it is the CD8α−CD4+ DC subset that supported protection against the disease. The lymphocytes from treated mice displayed more of a Th1 biased response. Both the protective subsets were mature and expressed significant levels of class II MHC and costimulatory molecules. However, the subsets trafficked differently to spleen and draining lymph nodes. Thus, distinct DC subsets drive tolerance in the two models of autoimmunity despite the fact that both diseases are mediated by CD4+ T cells. Research supported by grants DK65748 and NS37406 from NIH.

Artificially generated dendritic cells misdirect antiviral immune responses

Dendritic cells (DCs) are critical to the outcome of many viral infections. Questions still remain as to the relevance of artificially generated DCs in models of in vivo immune responses. We compared different DC generation pathways, in terms of phenotypic expression, cytokine production, apoptosis, and T cell proliferation, following viral infection. Direct viral infection of monocytes or monocytes cultured with supernatants from virally infected lung epithelial cells (A549 DCs) induce distinct DC subsets compared with viral infection of artificially generated IL-4 DCs and IFN-DCs. These virally infected DC subsets stimulated different cytokine secretion profiles and displayed contrasting sensitivities to viral-induced apoptosis. It is most interesting that we observed marked differences in the proliferation of purified CD3+ T cells from the virally infected DC subsets. In conclusion, artificially generated DCs skew immune responses to viral infections, and direct viral infection of monocytes and DCs, generated from monocytes cultured with supernatants from infected epithelial cells, appears to be a more relevant pathway of producing DCs, which mimic those generated in vivo.