DC Function Research Articles

Unleashing immune cells in tumors

Tumor Immunology Conventional type 1 dendritic cells (cDC1s) perform specialized roles in antitumor immunity by processing and presenting tumor antigens that prime tumor-specific T cell responses. Using a mouse model of immunogenic tumor growth and single-cell transcriptomics, Ghislat et al. found that cDC1s require nuclear factor κB signaling for their intratumoral maturation into antitumoral cDC1s capable of recruiting and activating tumor-specific T cells. A kinase controlled the expression of a transcription factor that regulates interferon-mediated gene expression, and loss of either factor in cDC1 impaired their maturation and antitumoral immunity. These results highlight key molecular pathways involved in the development of full-fledged cDC1 capable of stimulating antitumoral T cell responses and suggest potential therapeutic targets for improving intratumoral DC function. Sci. Immunol. 6 , eabg3570 (2021).

A Blood Dendritic Cell Vaccine for Acute Myeloid Leukemia Expands Anti-Tumour T Cell Responses at Remission

Many acute myeloid leukemia (AML) patients achieve a complete remission (CR) with chemotherapy, but relapse is common. Removal of residual disease remains the greatest challenge. The potential of the immune system to control chemotherapy resistant malignant cells is evident in the success of allogeneic transplantation (aTx), and early results with T cell checkpoint inhibition. However, these non-specific interventions lead to considerable morbidity.Dendritic cell (DC) vaccination has the potential to generate leukemia-specific autologous immunity with little toxicity. Promising results have been achieved with vaccines developed in vitro from purified monocytes (Mo-DC) delivered to patients with limited residual disease after conventional therapy. To stimulate an effective cytotoxic T cell response to exogenous proteins, DC must be able to cross-present protein antigen. We have demonstrated that pre-formed blood DC (BDC) have superior function to Mo-DC. Both Mo-DC and CD1c+ mDC sustained presentation of surface-loading peptide, FMP58-66, in the context of HLA class I for at least 16 hours. CD1c+ mDC presented the peptide at higher density than Mo-DC (p=0.0004). Most notably, CD1c+ mDC had a strikingly increased capacity to cross-present FMP54-74 long peptide as FMP58-66 bound to HLA-A2 at 16 hours compared with Mo-DC (p=0.0032).To assess the capacity to isolate and target DC in AML patients. We performed a visualised stochastic neighbour embedding (ViSNE) analysis that allowed us to directly compare healthy and patient BDC populations (HD, n=8, Relapsed refractory, n=6; in CR post-chemotherapy, n=18 or >12 months post-ATx, n=7) by visualising high dimensional cytometry data structures in two dimensions. All orthodox BDC subsets were identified in HD and AML CR patients, but were reduced in active AML. Within 12 weeks following chemotherapy, CD1c+ myeloid DC recovered while CD141+ DC and plasmacytoid DC showed partial recovery. We saw no significant difference in BDC subset recovery between different chemotherapy regimens used or in patients undergoing ATx.To determine whether the T cell landscape will permit an active vaccination strategy in AML CR patients, we compared patients receiving non-fludarabine regimens (NFR), fludarabine-containing regimens (FR) with those receiving those post-ATx with age-matched HD. Patients receiving NFR have relatively normal T cell number, phenotype and function at CR, whereas patients who have received FR as salvage therapy have persistent T cell abnormalities including reduced number, altered subset distribution, as well as a failure to expand and increased activation-induced cell death upon ligation of the T cell receptor. A comprehensive analysis of T cell landscape demonstrated increased PD-1 and TIM-3 on CD4+ T cells, particularly within the memory CD28+CD45RO+ population in FR (PD-1 p=0.0005, TIM-3 p=0.001) and ATx (PD-1 p=0.044, TIM-3 p=0.027) patients. In the NFR group there was a trend to increased PD-1 expression by CD4+ T cells (p=0.06, Figure 6A). Peripheral blood CD8+ T cells showed no significant increase in PD-1 or TIM-3 expression.We utilised the window of opportunity following induction of CR in NFR or ATx patients to combine active vaccination with BDC in combination with checkpoint inhibition against PD-1 and TIM-3. BDC priming was able to directly enhance functional T cell responses to viral (CMV, Influenza) and the tumour associated Wilms tumour 1 antigen, generating both CD4 and CD8 responses. Checkpoint blockade using anti-PD-1 and anti-TIM-3 antibodies demonstrated additive effects on the enhancement of antigen specific, cytotoxic, interferon gamma producing CD8+ T cells.The generation of capable functional responses in AML requires intact antigen processing and presentation as well functional effector T cells. In AML we have demonstrated that DC function is intact and there is a window of opportunity for active immune intervention in CR following either chemotherapy or ATx. Chemotherapy regimens have a profound impact on the function of effector T cells, notably fludarabine profoundly inhibits the capacity of T cells to respond to antigen priming and induces susceptibility to activation induced cell death. Clinical targeting with active DC vaccination in conjunction PD-1 and TIM-3 blockade may provide a new avenue for targeting residual disease and relapse in poor prognosis patients with AML. DisclosuresHart:DendroCyte BioTech Pty Ltd: Equity Ownership. Clark:DendroCyte BioTech Pty Ltd: Equity Ownership.

Commitment to dendritic cells and monocytes.

Dendritic cells (DCs) and monocytes are widely conserved immune cells in vertebrates that arise from hematopoietic stem cells via intermediate progenitors. The progenitors that strictly give rise to DCs or monocytes have been recently identified both in humans and in mice, thereby revealing their differentiation pathways. Advances in analysis technologies have further deepened our understanding of the development of DCs and monocytes from progenitor population-based to individual progenitor cell-based commitment. Since DC-committed progenitors, common DC progenitors (CDPs) and precursor conventional DCs (pre-cDCs) do not differentiate into monocytes, DCs are a distinct lineage from monocytes, although monocytes can acquire DC functions upon activation at tissues where they arrive.

Lipopolysaccharide-Activated Bone Marrow-Derived Dendritic Cells Suppress Allergic Airway Inflammation by Ameliorating the Immune Microenvironment.

BackgroundPrevious studies have shown that lipopolysaccharide (LPS)-activated bone marrow-derived dendritic cells (DClps) might induce tolerance in autoimmune and cancer models in vivo, whereas it remains unclear whether DClps could play a role in allergic disease model. Herein, we aimed to elucidate the potential effects of DClps on OVA-sensitized/challenged airway inflammation in a mouse model, which may help facilitate the application of specific tolerogenic dendritic cells (tolDC) in allergic asthma in the future.MethodsThe phenotype and function of immature DC (DCia), DClps or IL-10-activated-DC (DC10) were determined. OVA-sensitized/challenged mice were treated with OVA-pulsed DCia or DClps or DC10. We assessed the changes of histopathology, serum total IgE level, pulmonary signal transducers and activators of transcription (STAT), pulmonary regulatory T cells (Tregs), and airway recall responses to OVA rechallenge, including proliferation and cytokine secretory function of pulmonary memory CD4+ T cells in the treated mice.ResultsDClps exhibited low levels of CD80 and MHCII and increased levels of anti-inflammatory cytokines such as IL-10 and TGF-β. Additionally, DClps treatment dramatically diminished infiltration of inflammatory cells, eosinophilia, serum IgE and STAT6 phosphorylation level, increased the number of pulmonary Tregs. In addition, DClps treatment decreased the proliferation of pulmonary memory CD4+ T cells, which further rendered the downregulation of Th2 cytokines in vitro.ConclusionLPS stimulation may lead to a tolerogenic phenotype on DC, and thereby alleviated the Th2 immune response of asthmatic mice, possibly by secreting anti-inflammatory cytokines, inhibiting pulmonary memory CD4+ T cells, downregulating pulmonary STAT6 phosphorylation level and increasing pulmonary Tregs.

Modulation of lactate-lysosome axis in dendritic cells by clotrimazole potentiates antitumor immunity

BackgroundDendritic cells (DCs) play a critical role in antitumor immunity, but the therapeutic efficacy of DC-mediated cancer vaccine remains low, partly due to unsustainable DC function in tumor antigen presentation....

Androgen-associated increases in Bacteroides abundance correlate with enhanced immunoregulation and suppression of lupus in BWF1 mice.

Abstract Similar to humans, lupus incidence is higher in female than male NZBxNZW1(BWF1) mice, and castration abolishes male protection implicating androgens in disease suppression. Gut microbiota and metabolite compositions differ between female and male BWF1 mice; males have higher abundance of Bacteroides and the metabolites, phytol and phytanic acid (RXR agonists that can increase retinoic acid, RA). Male cecal transfers into females suppress disease which correlates with an increase in Bacteroides in recipients. In addition, female gut CD103+ dendritic cells (CD103+DC) have decreased ability to induce pTreg due to an RA deficiency (decreased RALDH2) that can be restored by male cecal transfer. The goal of this project was to study androgen effects on these processes. We found that male castration altered microbiota and metabolite compositions similarly to those found in female mice, e.g., reduced Bacteroides, and phytol and phytanic acid abundance. Castrated male cecal transfer did not suppress disease or increase Bacteroides abundance in recipients. As in females, castrated male CD103+DC had decreased ability to induce pTreg (decreased RALDH2) but induced high levels of IFNγ. And although androgen receptor mRNA was undetectable in CD103+DC, male mice treated with androgen receptor inhibitor (flutamide) had the same negative effect on CD103+DC function as castration, suggesting androgens affect CD103+DC indirectly. Interestingly, flutamide-treated and castrated male microbiota looked very similar, e.g., reduced Bacteroides. These data suggest that androgens in males increase Bacteroides abundance via receptor signaling in host cells that may in turn play a role in enhancing immunoregulation and suppressing lupus.

Dendritic cells dysfunction in tumor-draining lymph nodes

Abstract An effective anti-tumor response requires activation of both CD4 helper T cells (through MHC-II) and CD8 cytotoxic T cells (through MHC-I). Activation of tumor-specific T cells depends on tumor antigen presentation by DCs. However, it is known that the tumor microenvironment largely suppresses immune responses. The focus of our study is to characterize the functional status of DCs in tumor-draining lymph nodes and to identify the mechanisms that lead to defective presentation of tumor antigens. We transplanted tumors into the flank of mice and analyzed DCs from both tumor-draining lymph node (TDLN) and non-draining lymph nodes (NDLN) as our model system. Cross-presentation of OVA to CD8 T cells was not suppressed in TDLN in comparison to the NDLN either in vivo or ex vivo. However, both in vivo and ex vivo CD4 T cell activation by DCs from TDLNs was defective. Subset analysis revealed that both migratory and resident DCs in TDLN show a less mature phenotype as compared to their counterparts isolated from NDLN. Functional assays revealed defects in antigen uptake and processing in DCs from TDLN. We also identified differences in the proportion of MHC-II molecules containing the Invariant chain CLIP peptide in DCs from TDLN in comparison to NDLN. These features of DC function, supported by RNA-Seq analysis, contribute to defective antigen presentation to CD4 T cells and may explain the dysfunction of DCs in tumor-bearing mice. Further analysis should enable moving towards “correcting” DC defects that would allow CD4 T cell priming to provide help to anti-tumor CD8 T cells.

A Redistributed Bundle Algorithm Based on Local Convexification Models for Nonlinear Nonsmooth DC Programming

Abstract For nonlinear nonsmooth DC programming (difference of convex functions), we introduce a new redistributed proximal bundle method. The subgradient information of both the DC components is gathered from some neighbourhood of the current stability center and it is used to build separately an approximation for each component in the DC representation. Especially we employ the nonlinear redistributed technique to model the second component of DC function by constructing a local convexification cutting plane. The corresponding convexification parameter is adjusted dynamically and is taken sufficiently large to make the ”augmented” linearization errors nonnegative. Based on above techniques we obtain a new convex cutting plane model of the original objective function. Based on this new approximation the redistributed proximal bundle method is designed and the convergence of the proposed algorithm to a Clarke stationary point is proved. A simple numerical experiment is given to show the validity of the presented algorithm.

Fa(c)t checking: How fatty acids shape metabolism and function of macrophages and dendritic cells.

In recent years there have been major advances in our understanding of the role of free fatty acids (FAs) and their metabolism in shaping the functional properties of macrophages and DCs. This review presents the most recent insights into how cell intrinsic FA metabolism controls DC and macrophage function, as well as the current evidence of the importance of various exogenous FAs (such as polyunsaturated FAs and their oxidation products—prostaglandins, leukotrienes, and proresolving lipid mediators) in affecting DC and macrophage biology, by modulating their metabolic properties. Finally, we explore whether targeted modulation of FA metabolism of myeloid cells to steer their function could hold promise in therapeutic settings.

Exosomes Released From Human Bone Marrow-Derived Mesenchymal Stem Cell Attenuate Acute Graft-Versus-Host Disease After Allogeneic Hematopoietic Stem Cell Transplantation in Mice.

ObjectiveMesenchymal stromal cell–derived exosomes have been applied for the treatment of several immune diseases. This study aimed to explore the effect of human bone marrow–derived mesenchymal stem cell (hBMSC)–derived exosomes on acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT).MethodshBMSC were cultured, and the culture supernatants were then collected to prepare exosomes using total exosome isolation reagent from Invitrogen. Mouse aGVHD model was established by allogeneic cell transplantation and injected with hBMSC-derived exosomes (Msc-exo) via tail vein. Exosomes from human fibroblast (Fib-exo) were used as the treatment control. The effects of Msc-exo on dendritic cells, CD4+, and CD8+ T cells in aGVHD mice were analyzed through flow cytometry. The impact on inflammatory cytokines was tested by ELISA. Besides, the body weight, survival rate, and clinical score of treated mice were monitored.ResultsMsc-exo were successfully prepared. aGVHD mice injected with Msc-exo led to 7–8-fold increase of the CD8α+ conventional dendritic cells (cDCs) and CD11b+ cDCs compared with the controls. In addition, Msc-exo altered the T help and Treg subpopulation, and decreased the cytotoxicity and proliferation of cytotoxic T cells to favor inflammatory inhibition in aGVHD mice. Mice that received Msc-exo exhibited decreased weight loss and reduced aGVHD clinical score in a time-dependent manner as well as reduced lethality compared with Fib-exo treated or untreated control. Furthermore, the levels of IL-2, TNF-α, and IFN-γ were decreased, as well as the level of IL-10 was increased after Msc-exo treatment in vivo and in vitro.ConclusionhBMSC-derived exosomes could attenuate aGVHD damage and promote the survival of aGVHD mice by regulating the DC and T-cell subpopulation and function, and lead to inhibited inflammatory response in aGVHD mice.

Fetomaternal immune cross talk modifies T-cell priming through sustained changes to DC function

Prenatal exposure to infections can modify immune development. These environmental disturbances during early life potentially alter the incidence of inflammatory disorders as well as priming of immune responses. Infection with the helminth Schistosoma mansoni is widely studied for its ability to alter immune responsiveness and is associated with variations in coinfection, allergy, and vaccine efficacy in endemic populations. Exposure to maternal schistosomiasis during early life, even without transmission of infection, can result in priming effects on offspring immune responses to bystander antigenic challenges as related to allergic responsiveness and vaccination, with this article seeking to further clarify the effects and underlying immunologic imprinting. Here, we have combined a model of chronic maternal schistosomiasis infection with a thorough analysis of subsequent offspring immune responses to allergy and vaccination models, including viral challenge and steady-state changes to immune cell compartments. We have demonstrated that maternal schistosomiasis alters CD4+ responses during allergic sensitization and challenge in a skewed IL-4/B-cell-dominant response to antigenic challenge associated with limited inflammatory response. Beyond that, we have uncovered previously unidentified alterations to CD8+ T-cell responses during immunization that are dependent on vaccine formulation and have functional impact on the efficacy of vaccination against viral infection in a murine hepatitis B virus model. In addition to steady-state modifications to CD4+ T-cell polarization and B-cell priming, we have traced these modified CD8+ responses to an altered dendritic cell phenotype sustained into adulthood, providing evidence for complex priming effects imparted by infection via fetomaternal cross talk.

Human CD141+ dendritic cells (cDC1) are impaired in patients with advanced melanoma but can be targeted to enhance anti-PD-1 in a humanized mouse model

BackgroundThe conventional type 1 dendritic cell subset (cDC1) is indispensable for tumor immune responses and the efficacy of immune checkpoint inhibitor (ICI) therapies in animal models but little is known...

MicroRNA155 Plays a Critical Role in the Pathogenesis of Cutaneous Leishmania major Infection by Promoting a Th2 Response and Attenuating Dendritic Cell Activity

Interferon (IFN)-γ is indispensable in the resolution of cutaneous leishmaniasis (CL), while the Th2 cytokines IL-4, IL-10, and IL-13 mediate susceptibility. A recent study found that miR155, which promotes CD4+ Th1 response and IFN-γ production, is dispensable in the control of Leishmania donovani infection. Here, the role of miR155 in CL caused by L. major was investigated using miR155-deficient (miR155-/-) mice. Infection was controlled significantly quicker in the miR155-/- mice than in their wild-type (WT) counterparts, indicating that miR155 contributes to the pathogenesis of CL. Faster resolution of infection in miR155-/- mice was associated with increased levels of Th1-associated IL-12 and IFN-γ and reduced production of Th2- associated IL-4, IL-10, and IL-13. Concentrations of IFN-γ+CD8+ T cells and natural killer cells in draining lymph nodes were significantly higher in the L. major-infected miR155-/- mice than in the infected WT mice, as indicated by flow-cytometry. After invitro IFN-γ stimulation, nitric oxide and IL-12 production were increased, IL-10 production was decreased, and parasite clearance was enhanced in L. major-infected miR155-/- DCs compared to those in WT DCs. Furthermore, IFN-γ production from activated miR155-/- T cells was significantly enhanced in L. major-infected miR155-/- DCs. Together, these findings demonstrate that miR155 promotes susceptibility to CL caused by L. major by promoting Th2 response and inhibiting DC function.

Optimality conditions and DC-Dinkelbach-type algorithm for generalized fractional programs with ratios of difference of convex functions

In this paper, we develop optimality conditions and propose an algorithm for generalized fractional programming problems whose objective function is the maximum of finite ratios of difference of convex (dc) functions, with dc constraints, that we will call later, DC-GFP. Such problems are generally nonsmooth and nonconvex. We first give in this work, optimality conditions for such problems, by means of convex analysis tools. For solving DC-GFP, the use of Dinkelbach-type algorithms conducts to nonconvex subproblems, which causes the failure of the latter since it requires finding a global minimum for these subprograms. To overcome this difficulty, we propose a DC-Dinkelbach-type algorithm in which we overestimate the objective function in these subproblems by a convex function, and the constraints set by an inner convex subset of the latter, which leads to convex subproblems. We show that every cluster point of the sequence of optimal solutions of these subproblems satisfies necessary optimality conditions of KKT type. Finally we end with some numerical tests to illustrate the behavior of our algorithm.

The role of \u03b22 integrin in dendritic cell migration during infection

BackgroundDendritic cells (DCs) play a key role in shaping T cell responses. To do this, DCs must be able to migrate to the site of the infection and the lymph nodes to prime T cells and initiate the appropriate immune response. Integrins such as β2 integrin play a key role in leukocyte adhesion, migration, and cell activation. However, the role of β2 integrin in DC migration and function in the context of infection-induced inflammation in the gut is not well understood. This study looked at the role of β2 integrin in DC migration and function during infection with the nematode worm Trichuris muris. Itgb2tm1Bay mice lacking functional β2 integrin and WT littermate controls were infected with T. muris and the response to infection and kinetics of the DC response was assessed.ResultsIn infection, the lack of functional β2 integrin significantly reduced DC migration to the site of infection but not the lymph nodes. The lack of functional β2 integrin did not negatively impact T cell activation in response to T. muris infection.ConclusionsThis data suggests that β2 integrins are important in DC recruitment to the infection site potentially impacting the initiation of innate immunity but is dispensible for DC migration to lymph nodes and T cell priming in the context of T. muris infection.

RIG-I–Like Receptor LGP2 Is Required for Tumor Control by Radiotherapy

Dendritic cells (DC) play an essential role in innate immunity and radiation-elicited immune responses. LGP2 is a RIG-I-like receptor involved in cytoplasmic RNA recognition and antiviral responses. Although LGP2 has also been linked to cell survival of both tumor cells and T cells, the role of LGP2 in mediating DC function and antitumor immunity elicited by radiotherapy remains unclear. Here, we report that tumor DCs are linked to the clinical outcome of patients with breast cancer who received radiotherapy, and the presence of DC correlates with gene expression of LGP2 in the tumor microenvironment. In preclinical models, host LGP2 was essential for optimal antitumor control by ionizing radiation (IR). The absence of LGP2 in DC dampened type I IFN production and the priming capacity of DC. In the absence of LGP2, MDA5-mediated activation of type I IFN signaling was abrogated. The MDA5/LGP2 agonist high molecular weight poly I:C improved the antitumor effect of IR. This study reveals a previously undefined role of LGP2 in host immunity and provides a new strategy to improve the efficacy of radiotherapy. SIGNIFICANCE: These findings reveal an essential role of LGP2 in promoting antitumor immunity after radiotherapy and provide a new strategy to enhance radiotherapy.

Mycophenolic acid, the active form of mycophenolate mofetil, interferes with IRF7 nuclear translocation and type I IFN production by plasmacytoid dendritic cells

BackgroundBoth humoral and cellular immune mechanisms are involved in the onset and progression of autoimmune responses in systemic lupus erythematosus (SLE). Plasmacytoid dendritic cells (pDCs) play a central role in the pathogenesis of SLE via the dysregulation of type I interferon (IFN) production; these cells act together with activated myeloid DCs (mDCs) to amplify the vicious pathogenic spiral of autoimmune disorders. Therefore, control of aberrant DC activation in SLE may provide an alternative treatment strategy against this disease. Mycophenolate mofetil (MMF), which has been used to treat lupus nephritis, specifically blocks the proliferation of B and T lymphocytes via inhibition of inosine-5-monophosphate dehydrogenase. Here, we focus on the effects of MMF in targeting DC functions, especially the IFN response of pDCs.MethodsWe isolated human blood pDCs and mDCs by flow cytometry and examined the effect of mycophenolic acid (MPA), which is a metabolic product of MMF, on the toll-like receptor (TLR) ligand response of DC subsets. Additionally, we cultured pDCs with serum from SLE patients in the presence or absence of MPA and then examined the inhibitory function of MPA on SLE serum-induced IFN-α production.ResultsWe found that treatment with 1−10 μM of MPA (covering the clinical trough plasma concentration range) dose-dependently downregulated the expression of CD80 and CD86 on mDCs (but not pDCs) without inducing apoptosis, in response to R848 or CpG-ODN, respectively. Notably, in pDCs, MPA significantly suppressed IFN-α production with IRF7 nuclear translocation and repressed the AKT activity. In addition, MPA inhibited IL-12 production with STAT4 expression in mDCs. We further identified that MPA had an inhibitory effect on SLE serum-induced IFN-α production by pDCs.ConclusionsOur data suggest that MPA can interrupt the vicious pathogenic spiral of autoimmune disorders by regulating the function of DC subsets. This work unveiled a novel mechanism for the therapeutic ability of MMF against SLE.

The regulatory role of peripheral blood mononuclear cell function by A20

Peripheral blood mononuclear cells (PBMC) consist of lymphocytes (T cells, B cells, natural killer cells), monocytes and dendritic cells and play important roles in initiating and regulating immunity against pathogens or immunotolerance to allergens. Activation of PBMCs is induced upon exposure to multiple stimuli by the binding with toll-like receptors (TLRs), recognition elements of the innate immune system. A20 is a negative regulator of nuclear factor (NF)-κB-dependent immune reaction in response to TLR ligands. A20-deficient mice display severe inflammation, tissue damage in multiple organs, cachexia and premature mortality. Single nucleotide polymorphisms (SNPs) at A20 gene region in humans reduce the binding capacity of A20 to NF‐κB subunits, resulting in reduced expression and function of A20 and leading to the pathogenesis of autoimmune and cancers. Although the inhibitory role of A20 on immune cells including B, T and DC functions has been previously reported, the effect of A20 on PBMC function is not mentioned yet. The present study, therefore, explored whether A20 expression is involved in immunophenotypic changes, the release of cytokine production, cell migration, and apoptosis. To this end, immonophenotypic profile and cell apoptosis were examined by flow cytometry, secretion of inflammatory cytokines by ELISA and cell migration by a transwell migration assay. As a result, percentages of CD3+CD25+, CD19+CD25+, and CD11b+CD40+ expressing cells, the release of TNF-α and IL-1β and cell migration were enhanced in A20-silenced PBMCs. However, cell apoptosis was independent of the presence of A20 in PBMCs. In conclusion, these results attained in this study suggested that A20 expression might modulate the immune response in autoimmune disease and cancers.

The ABC of DC Programming

A function is called DC if it is expressible as the difference of two convex functions. In this work, we present a short tutorial on difference-of-convex optimization surveying and highlighting some important facts about DC functions, optimality conditions, and recent algorithms. The manuscript, accessible to a wide range of readers familiar with the convex analysis machinery, builds upon three pillars from variational analysis: directional derivative, e-subdifferential, and the Legendre-Fenchel transform.

Dendritic cell-derived TGF-β mediates the induction of mucosal regulatory T-cell response to Helicobacter infection essential for maintenance of immune tolerance in mice.

Helicobacter pylori infection leads to regulatory T-cell (Treg) induction in infected mice, which contributes to H. pylori immune escape. However, the mechanisms responsible for H. pylori induction of Treg and immune tolerance remain unclear. We hypothesized DC-produced TGF-β may be responsible for Treg induction and immune tolerance. To test this hypothesis, we generated TGF-β∆DC mice (CD11c+ DC-specific TGF-β deletion) and assessed the impact of DC-specific TGF-β deletion on DC function during Helicobacter infection in vitro and in vivo. To examine the T cell-independent DC function, we crossed TGF-β∆DC mice onto Rag1KO background to generate TGF-β∆DC xRag1KO mice. When stimulated with H. pylori, TGF-β∆DC BMDC/splenocyte cocultures showed increased levels of proinflammatory cytokines and decreased levels of anti-inflammatory cytokines compared to control, indicating a proinflammatory DC phenotype. Following 6months of H. felis infection, TGF-β∆DC mice developed more severe gastritis and a trend toward more metaplasia compared to TGF-βfl/fl with increased levels of inflammatory Th1 cytokine mRNA and lower gastric H. felis colonization compared to infected TGF-βfl/fl mice. In a T cell-deficient background using TGF-β∆DC xRag1KO mice, H. felis colonization was significantly lower when DC-derived TGF-β was absent, revealing a direct, innate function of DC in controlling H. felis infection independent of Treg induction. Our findings indicate that DC-derived TGF-β mediates Helicobacter-induced Treg response and attenuates the inflammatory Th1 response. We also demonstrated a previously unrecognized innate role of DC controlling Helicobacter colonization via a Treg-independent mechanism. DC TGF-β signaling may represent an important target in the management of H. pylori.