Project description:Transcriptome analysis of IFNγ-insensitive DCs IFNγ signaling drives dendritic cells (DCs) to promote type I T cell (Th1) immunity. Here, we show that activation of DCs by IFNγ is equally crucial for the differentiation of a population of T-bet+ regulatory T (Treg) cells specialized to inhibit Th1 immune responses. Conditional deletion of IFNγ receptor in DCs but not in Treg cells resulted in a severe defect in this specific Treg cell subset, leading to exacerbated immune pathology during parasitic infections. Mechanistically, IFNγ-unresponsive DCs failed to produce sufficient amount of IL-27, a cytokine required for optimal T-bet induction in Treg cells. Thus, IFNγ signalling endows DCs with the ability to efficiently control a specific type of T cell immunity through promoting a corresponding Treg cell population. We analyzed saliva from 3 WT DC samples and 3 IFNγR2 KO DC samples isolated from unmanipulated mice. In addition, we analyzed saliva from 3 WT DC samples and 3 IFNγR2 KO DC samples isolated from mixed BM chimeras (WT + IFNgR2KO) day 8 T. gondii infected.
Project description:IFN? signaling drives dendritic cells (DCs) to promote type I T cell (Th1) immunity. Here, we show that activation of DCs by IFN? is equally crucial for the differentiation of a population of T-bet+ regulatory T (Treg) cells specialized to inhibit Th1 immune responses. Conditional deletion of IFN? receptor in DCs but not in Treg cells resulted in a severe defect in this specific Treg cell subset, leading to exacerbated immune pathology during parasitic infections. Mechanistically, IFN?-unresponsive DCs failed to produce sufficient amount of IL-27, a cytokine required for optimal T-bet induction in Treg cells. Thus, IFN? signalling endows DCs with the ability to efficiently control a specific type of T cell immunity through promoting a corresponding Treg cell population.
Project description:Introduction: Ovarian cancer is one of the most lethal gynecologic cancers. Relapses after remission are common, hence novel strategies are urgently needed. Our group has previously developed a vaccination approach based on dendritic cells pulsed with HOCl-oxidized tumor lysates. Here we investigate the improvement of this vaccine strategy using squaric acid treatment of cancer cells during tumor lysate preparation and by differentiating dendritic cells in the presence of GM-CSF and IFNα. Methods: Induction of cell death by squaric acid treatment was assessed with propidium iodide (PI) and Annexin V in ID8 tumor cells. High mobility group box 1 (HMGB1) immunogenic status was analyzed using a western blot-based method, as previously described. For immunological tests, ID8 cells expressing ovalbumin (ova-ID8) were treated with squaric acid before cell lysis. DCs prepared with the canonical GM-CSF and IL-4 differentiation cocktail or IFNα and GM-CSF were pulsed with tumor cell lysates and further matured in the presence of IFNγ and LPS (4-DCs and α-DCs respectively). DCs were then used in co-culture assays with ova-specific T cells and IFNγ and IL-4 secretion measured by ELISA. DC phenotypes were characterized by FACS. Finally, DCs were tested in an ovarian cancer mouse model measuring body weight and animal survival. Results: Squaric acid treatment of mouse ovarian cancer cells induced tumor cell death as well as preserve HMGB1, a crucial Damage-associated molecular pattern (DAMP) signal, in its active reduced form. Squaric acid treatment of ID8-ova cells increased IFNγ and decreased IL-4 production from ova-specific T cells in co-culture experiments, promoting a more immunogenic cytokine secretion pattern. DCs differentiated in the presence of IFNα induced a considerable decrease in IL-4 production compared to canonical 4-DCs, without affecting IFNγ release. DC phenotyping demonstrated a more mature and immunogenic phenotype for IFNα-differentiated DCs. Vaccination in tumor-bearing mice showed that IFNα-differentiated DCs pulsed with squaric acid-treated lysates were the most potent at delaying tumor growth, improving animal survival. Conclusion: We identified squaric acid as a novel immunogenic treatment of tumor cells for cancer vaccines particularly efficient in prolonging animal survival when used in combination with IFNα-differentiated DCs. These promising results support future efforts for the clinical translation of this approach.
Project description:We previously described a mouse model of ulcerative colitis linked to T-bet deficiency in the innate immune system. Here, we report that the majority of T-bet(-/-)RAG2(-/-) ulcerative colitis (TRUC) mice spontaneously progress to colonic dysplasia and rectal adenocarcinoma solely as a consequence of MyD88-independent intestinal inflammation. Dendritic cells (DCs) are necessary cellular effectors for a proinflammatory program that is carcinogenic. Whereas these malignancies arise in the setting of a complex inflammatory environment, restoration of T-bet selectively in DCs was sufficient to reduce colonic inflammation and prevent the development of neoplasia. TRUC colitis-associated colorectal cancer resembles the human disease and provides ample opportunity to probe how inflammation drives colorectal cancer development and to test preventative and therapeutic strategies preclinically.
Project description:Statins, best known for their lipid-lowering actions, also possess immunomodulatory properties. Recent studies have shown a Th2-biasing effect of statins, although the underlying mechanism has not been identified. In this study, we investigated whether simvastatin can exercise a Th2-promoting effect through modulation of function of dendritic cells (DCs) without direct interaction with CD4+ T cells. Exposure of DCs to simvastatin induced the differentiation of a distinct subset of DCs characterized by a high expression of B220. These simvastatin-conditioned DCs up-regulated GATA-3 expression and down-regulated T-bet expression in cocultured CD4+ T cells in the absence of additional simvastatin added to the coculture. The Th2-biased transcription factor profile induced by simvastatin-treated DCs also was accompanied by increased Th2 (IL-4, IL-5, and IL-13) and decreased Th1 (IFN-gamma) cytokine secretion from the T cells. The Th2-promoting effect of simvastatin was found to depend on the chitinase family member Ym1, known to be a lectin. Anti-Ym1 antibody abolished the Th2-promoting effect of simvastatin-treated DCs. Also, simvastatin was unable to augment Ym1 expression in DCs developed from STAT6-/- or IL-4R alpha-/- mice. Thus, modulation of Ym1 production by DCs identifies a previously undescribed mechanism of Th2 polarization by statin.
Project description:Parasitic helminths evade, skew and dampen human immune responses through numerous mechanisms. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effects that soluble egg antigen (SEA) from Schistosoma mansoni had on modulating HIV-1 infection and cytokine/chemokine production in vitro. We determined that SEA, specifically through kappa-5, can potently bind to DC-SIGN and thereby blocks DC-SIGN mediated HIV-1 trans-infection (p<0.05) whilst not interfering with cis-infection. DCs exposed to SEA whilst maturing under Th2 promoting conditions, will upon co-culture with naïve T-cells induce a T-cell population that was less susceptible to HIV-1 R5 infection (p<0.05) compared to DCs unexposed to SEA, whereas HIV-1 X4 virus infection was unaffected. This was not observed for DCs exposed to SEA while maturing under Th1 or Th1/Th2 (Tmix) promoting conditions. All T-cell populations induced by SEA exposed DCs demonstrate a reduced capacity to produce IFN-? and MIP-1?. The infection profile of T-cells infected with HIV-1 R5 was not associated with down-modulation of CCR5 cell surface expression. We further show that DCs maturing under Tmix conditions exposed to plant recombinant omega-1 protein (r?-1), which demonstrates similar functions to natural ?-1, induced T-cell populations that were less sensitive for HIV-1 R5 infection (p<0.05), but not for X4 virus infection. This inhibition associated again with a reduction in IFN-? and MIP-1? expression, but additionally correlated with reduced CCR5 expression. We have shown that SEA parasite antigens and more specifically r?-1 can modulate HIV-1 infectivity with the potential to influence disease course in co-infected individuals.
Project description:Dendritic cells (DCs) play an important role in advancing age-associated progressive decline in adaptive immune responses, loss of tolerance, and development of chronic inflammation. In aged humans, DCs secrete increased levels of pro-inflammatory cytokines and decreased levels of anti-inflammatory and immune-regulatory cytokines. This may contribute to both chronic inflammation and loss of tolerance in aging. Aged DCs also display increased immune response against self-antigens contributing further to both inflammation and loss of tolerance. The secretion of innate protective cytokines such as type I and III interferons is decreased, and the function of DCs in airway remodeling and inflammation in aged is also compromised. Furthermore, the capacity of DCs to prime T cell responses also seems to be affected. Collectively, these changes in DC functions contribute to the immune dysfunction and inflammation in the elderly. This review only focuses on age-associated changes in DC function in humans.
Project description:Atopic asthma is an inflammatory pulmonary disease associated with Th2 adaptive immune responses triggered by innocuous antigens. While dendritic cells (DCs) are known to shape the adaptive immune response, the mechanisms by which DCs promote Th2 differentiation remain elusive. Herein we demonstrate that Th2-promoting stimuli induce DC expression of IRF4. Mice with conditional deletion of Irf4 in DCs show a dramatic defect in Th2-type lung inflammation, yet retain the ability to elicit pulmonary Th1 antiviral responses. Using loss- and gain-of-function analysis, we demonstrate that Th2 differentiation is dependent on IRF4 expression in DCs. Finally, IRF4 directly targets and activates the Il-10 and Il-33 genes in DCs. Reconstitution with exogenous IL-10 and IL-33 recovers the ability of Irf4-deficient DCs to promote Th2 differentiation. These findings reveal a regulatory module in DCs by which IRF4 modulates IL-10 and IL-33 cytokine production to specifically promote Th2 differentiation and inflammation.
Project description:Myeloid dendritic cells (mDCs) are the antigen-presenting cells best capable of promoting peripheral induction of regulatory T cells (Tregs), and are among the first targets of HIV. It is thus important to understand whether HIV alters their capacity to promote Treg conversion. Monocyte-derived DCs (moDCs) from uninfected donors induced a Treg phenotype (CD25(+)FOXP3(+)) in autologous conventional T cells. These converted FOXP3(+) cells suppressed the proliferation of responder T cells similarly to circulating Tregs. In contrast, the capacity of moDCs to induce CD25 or FOXP3 was severely impaired by their in vitro infection with CCR5-utilizing virus. MoDC exposure to inactivated HIV was sufficient to impair FOXP3 induction. This DC defect was not dependent on IL-10, TGF-? or other soluble factors, but was due to preferential killing of Tregs by HIV-exposed/infected moDCs, through a caspase-dependent pathway. Importantly, similar results were obtained with circulating primary myeloid DCs. Upon infection in vitro, these mDCs also killed Treg through mechanisms at least partially caspase-dependent, leading to a significantly lower proportion of induced Tregs. Taken together, our data suggest that Treg induction may be defective when DCs are exposed to high levels of virus, such as during the acute phase of infection or in AIDS patients.
Project description:The contribution of natural killer (NK) cells to the treatment efficacy of dendritic cell (DC)-based cancer vaccines is being increasingly recognized. Much current efforts to optimize this form of immunotherapy are therefore geared towards harnessing the NK cell-stimulatory ability of DCs. In this study, we investigated whether generation of human monocyte-derived DCs with interleukin (IL)-15 followed by activation with a Toll-like receptor stimulus endows these DCs, commonly referred to as "IL-15 DCs", with the capacity to stimulate NK cells. In a head-to-head comparison with "IL-4 DCs" used routinely for clinical studies, IL-15 DCs were found to induce a more activated, cytotoxic effector phenotype in NK cells, in particular in the CD56bright NK cell subset. With the exception of GM-CSF, no significant enhancement of cytokine/chemokine secretion was observed following co-culture of NK cells with IL-15 DCs. IL-15 DCs, but not IL-4 DCs, promoted NK cell tumoricidal activity towards both NK-sensitive and NK-resistant targets. This effect was found to require cell-to-cell contact and to be mediated by DC surface-bound IL-15. This study shows that DCs can express a membrane-bound form of IL-15 through which they enhance NK cell cytotoxic function. The observed lack of membrane-bound IL-15 on "gold-standard" IL-4 DCs and their consequent inability to effectively promote NK cell cytotoxicity may have important implications for the future design of DC-based cancer vaccine studies.