Dendritic cells control CD4+CD25+ Treg cell suppressor function in vitro through juxtacrine delivery of IL-2

CD83 orchestrates immunity toward self and non-self in dendritic cells

Dendritic cells (DCs) are crucial to balance protective immunity and autoimmune inflammatory processes. Expression of CD83 is a well-established marker for mature DCs, although its physiological role is still not completely understood. Using a DC-specific CD83-conditional KO (CD83ΔDC) mouse, we provide new insights into the function of CD83 within this cell type. Interestingly, CD83-deficient DCs produced drastically increased IL-2 levels and displayed higher expression of the costimulatory molecules CD25 and OX40L, which causes superior induction of antigen-specific T cell responses and compromises Treg suppressive functions. This also directly translates into accelerated immune responses in vivo. Upon Salmonella typhimurium and Listeria monocytogenes infection, CD83ΔDC mice cleared both pathogens more efficiently, and CD83-deficient DCs expressed increased IL-12 levels after bacterial encounter. Using the experimental autoimmune encephalomyelitis model, autoimmune inflammation was dramatically aggravated in CD83ΔDC mice while resolution of inflammation was strongly reduced. This phenotype was associated with increased cell influx into the CNS accompanied by elevated Th17 cell numbers. Concomitantly, CD83ΔDC mice had reduced Treg numbers in peripheral lymphoid organs. In summary, we show that CD83 ablation on DCs results in enhanced immune responses by dysregulating tolerance mechanisms and thereby impairing resolution of inflammation, which also demonstrates high clinical relevance.

Modulation of innate immunity by cyclosporine A

Cyclosporine A has long been known to suppress T cell responses by inhibiting the production of IL-2, which drives T cell proliferation, enabling its use as a therapeutic for transplantation or autoimmunity. However, cyclosporine A also impacts on innate immune cells including dendritic cells, macrophages and neutrophils. In dendritic cells, which are essential for T cell priming, cyclosporine A can modulate both expression of surface molecules that engage with T cells and cytokine secretion, leading to altered induction of T cell responses. In macrophages and neutrophils, which play key antimicrobial roles, cyclosporine A reduces the production of cytokines that can play protective roles against pathogens. Some of these molecules, if produced in the context of chronic disease, can also contribute to pathology. There have been a number of elegant recent studies addressing the mechanisms by which cyclosporine A can modulate innate immunity. In particular, cyclosporine A inhibits the release of mitochondrial factors that stimulate the production of type 1 interferons by innate immune cells. This review addresses the emerging literature on modulation of innate immune responses by cyclosporine A, its resultant impact on adaptive immune responses and how this offers potential for new therapeutic applications.

Immunomodulatory Effect of Nigella sativa Oil on T Lymphocytes in Patients with Rheumatoid Arthritis

BACKGROUND AND OBJECTIVES

Abundant evidence indicates the involvement of CD4(+), CD8(+), and CD4(+)CD25(+) T lymphocytes in the induction and/or protection of rheumatoid arthritis (RA). We aimed to investigate the modulatory effect of Nigella sativa (NS) oil on the selected T cell subset percentage in females with RA.

METHODS

A randomized, double-blinded placebo-controlled, 2 months, parallel-group clinical trial was conducted. Forty-three female patients (20-50 years) with mild to moderate RA were recruited and assigned into NS (n = 23) and placebo (n = 20) groups to receive one gram of NS oil, or starch, capsule in two divided doses, respectively. The disease activity scores of 28 joints (DAS28) were calculated and percentages of CD4(+), CD8(+), and CD4(+)CD25(+) T cells were examined using flow cytometry.

RESULTS

Treatment with NS led to significant reduction of the serum high-sensitivity C-reactive protein (hs-CRP) level and DAS-28 score and an improved number of swollen joints compared with baseline and placebo groups. A relatively comparable CD4(+) T cell percentage was observed in the NS and placebo groups either in baseline or the end of study. The treatment also resulted in reduced CD8(+), and increased CD4(+)CD25(+) T cell percentage and the CD4(+)/CD8(+) ratio as compared to placebo and baseline. A negative significant correlation between changes in CD8(+) and changes in CD4(+)CD25(+) T cells and a positive significant correlation between changes in CD4(+)CD25(+) T cells and changes in the CD4(+)/CD8(+) ratio was observed in the NS group.

CONCLUSION

This study gives strength to the potential relevance of NS in clinical management of RA through modulation of T lymphocytes.

Beyond regulatory T cells: the potential role for IL-2 to deplete T-follicular helper cells and treat autoimmune diseases

Low-dose IL-2 administration suppresses unwanted immune responses in mice and humans, thus evidencing the potential of IL-2 to treat autoimmune disorders. Increased Tregs activity is one of the potential mechanisms by which low-dose IL-2 immunotherapy induces immunosuppression. In addition, recent data indicate that IL-2 may contribute to prevent unwanted self-reactive responses by preventing the developing of T-follicular helper cells, a CD4(+) T-cell subset that expands in autoimmune disease patients and promotes long-term effector B-cell responses. Here we discuss the mechanisms underlying the clinical benefits of low-dose IL-2 administration, focusing on the role of this cytokine in promoting Treg-mediated suppression and preventing self-reactive T-follicular helper cell responses.

Oxidized high-density lipoprotein accelerates atherosclerosis progression by inducing the imbalance between treg and teff in LDLR knockout mice

High density lipoprotein (HDL) dysfunction has been widely reported in clinic, and oxidation of HDL (ox-HDL) was shown to be one of the most common modifications in vivo and participate in the progression of atherosclerosis. But the behind mechanisms are still elusive. In this study, we firstly analyzed and found strong relationship between serum ox-HDL levels and risk factors of coronary artery diseases in clinic, then the effects of ox-HDL in initiation and progression of atherosclerosis in LDLR knockout mice were investigated by infusion of ox-HDL dissolved in chitosan hydrogel before the formation of lesions in vivo. Several new evidence were shown: (i) the serum levels of ox-HDL peaked early before the formation of lesions in LDLR mice fed with high fat diet similar to oxidative low density lipoprotein, (ii) the formation of atherosclerotic lesions could be accelerated by infusion of ox-HDL, (iii) the pro-atherosclerotic effects of ox-HDL were accompanied by imbalanced levels of effector and regulatory T cells and relative gene expressions, which implied that imbalance of teff and treg might contribute to the pro-atherosclerosis effects of ox-HDL.

Thymic regulatory T cell niche size is dictated by limiting IL-2 from antigen-bearing dendritic cells and feedback competition

The thymic production of regulatory T cells (Treg cells) requires interleukin 2 (IL-2) and agonist T cell antigen receptor (TCR) ligands and is controlled by competition for a limited developmental niche, but the thymic sources of IL-2 and the factors that limit access to the niche are poorly understood. Here we found that IL-2 produced by antigen-bearing dendritic cells (DCs) had a key role in Treg cell development and that existing Treg cells limited new development of Treg cells by competing for IL-2. Our data suggest that antigen-presenting cells (APCs) that can provide both IL-2 and a TCR ligand constitute the thymic niche and that competition by existing Treg cells for a limited supply of IL-2 provides negative feedback for new production of Treg cells.

Activation of the arylhydrocarbon receptor causes immunosuppression primarily by modulating dendritic cells

UVR suppresses the immune system in an antigen-specific manner via induction of regulatory T cells (Tregs). The specific immunosuppression by UVR harbors therapeutic potential but is associated with UVR-induced DNA damage, requiring the identification of other triggers inducing the same immunosuppressive effects without DNA damage. The aryl hydrocarbon receptor (AhR) was identified as a molecular target for UVR and its activation to be involved in UVR-induced immunosuppression. Accordingly, the AhR agonist 4-n-nonylphenol (NP) suppressed sensitization and induced Treg similar to UVR. Here we show that antigen-presenting cells are critically involved in AhR-induced immunosuppression. Injection of hapten-coupled dendritic cells (DCs) treated with NP into mice did not result in sensitization but induced Treg. NP induced the release of IL-2 by DC that subsequently triggered the release of IL-10. NP upregulated the negative regulatory molecule B7-H4 via the release of IL-2 that was functionally relevant as inhibition of B7-H4 prevented the induction of Treg. Together, this indicates that activation of the AhR switches antigen-presenting cells from a stimulatory into a regulatory phenotype, ultimately inducing Treg. Thus, AhR agonists may represent an alternative to suppress the immune system like UVR but without causing the adverse effects of UVR including DNA damage.

IL-33 is an unconventional Alarmin that stimulates IL-2 secretion by dendritic cells to selectively expand IL-33R/ST2+ regulatory T cells

IL-33 is a recently characterized IL-1 family member that is proposed to function as an alarmin, or endogenous signal of cellular damage, as well as act as a pleiotropic cytokine. The ability of IL-33 to potentiate both Th1 and Th2 immunity supports its role in pathogen clearance and disease immunopathology. Yet, IL-33 restrains experimental colitis and transplant rejection by expanding regulatory T cells (Treg) via an undefined mechanism. We sought to determine the influence of IL-33 on hematopoietic cells that drives Treg expansion and underlies the therapeutic benefit of IL-33 administration. In this study, we identify a feedback loop in which conventional mouse CD11c(+) dendritic cells (DC) stimulated by IL-33 secrete IL-2 to selectively expand IL-33R(ST2(+))- suppressive CD4(+)Foxp3(+) Treg. Interestingly, this occurs in the absence of classical DC maturation, and DC-derived (innate) IL-2 increases ST2 expression on both DC and interacting Treg. ST2(+) Treg represent an activated subset of Foxp3(+) cells, demonstrated to be ICOS(high)CD44(high) compared with their ST2(-) counterparts. Furthermore, although studies have shown that IL-33-exposed DC promote Th2 responses, we reveal that ST2(+) DC are required for IL-33-mediated in vitro and in vivo Treg expansion. Thus, we have uncovered a relationship between IL-33 and innate IL-2 that promotes the selective expansion of ST2(+) Treg over non-Treg. These findings identify a novel regulatory pathway driven by IL-33 in immune cells that may be harnessed for therapeutic benefit or for robust expansion of Treg in vitro and in vivo.

Phenotype and polarization of autologous T cells by biomaterial-treated dendritic cells

Given the central role of dendritic cells (DCs) in directing T-cell phenotypes, the ability of biomaterial-treated DCs to dictate autologous T-cell phenotype was investigated. In this study, we demonstrate that differentially biomaterial-treated DCs differentially directed autologous T-cell phenotype and polarization, depending on the biomaterial used to pretreat the DCs. Immature DCs (iDCs) were derived from human peripheral blood monocytes and treated with biomaterial films of alginate, agarose, chitosan, hyaluronic acid, or 75:25 poly(lactic-co-glycolic acid) (PLGA), followed by co-culture of these biomaterial-treated DCs and autologous T cells. When autologous T cells were co-cultured with DCs treated with biomaterial film/antigen (ovalbumin, OVA) combinations, different biomaterial films induced differential levels of T-cell marker (CD4, CD8, CD25, CD69) expression, as well as differential cytokine profiles [interferon (IFN)-γ, interleukin (IL)-12p70, IL-10, IL-4] in the polarization of T helper (Th) types. Dendritic cells treated with agarose films/OVA induced CD4+CD25+FoxP3+ (T regulatory cells) expression, comparable to untreated iDCs, on autologous T cells in the DC-T co-culture system. Furthermore, in this co-culture, agarose treatment induced release of IL-12p70 and IL-10 at higher levels as compared with DC treatment with other biomaterial films/OVA, suggesting Th1 and Th2 polarization, respectively. Dendritic cells treated with PLGA film/OVA treatment induced release of IFN-γ at higher levels compared with that observed for co-cultures with iDCs or DCs treated with all other biomaterial films. These results indicate that DC treatment with different biomaterial films has potential as a tool for immunomodulation by directing autologous T-cell responses.

Self-antigen presentation by dendritic cells in autoimmunity

The operation of both central and peripheral tolerance ensures the prevention of autoimmune diseases. The maintenance of peripheral tolerance requires self-antigen presentation by professional antigen presenting cells (APCs). Dendritic cells (DCs) are considered as major APCs involved in this process. The current review discusses the role of DCs in autoimmune diseases, the various factors involved in the induction and maintenance of tolerogenic DC phenotype, and pinpoints their therapeutic capacity as well as potential novel targets for future clinical studies.

Cytokine correlation between sinus tissue and nasal secretions among chronic rhinosinusitis and controls

OBJECTIVES/HYPOTHESIS

Compare cytokine levels in sinus tissue to sinus secretions from controls and chronic rhinosinusitis patients.

STUDY DESIGN

In vitro.

METHODS

Polyurethane foam sponges were placed into middle meati of patients with chronic rhinosinusitis without nasal polyps (CRSsNP), with polyps (CRSwNP), and controls. Sinus biopsies were then taken from the same location. Protein levels of tumor necrosis factor-alpha (TNF-α), interferon-γ (IFN-γ), and interleukins (IL) 2, 4, 6, 8, 10, and 17A were measured via cytometric bead assay for each sample. Protein values from sinus tissue and secretions were compared with Pearson's correlation between samples as well as one-way ANOVA with posthoc t test between groups.

RESULTS

Samples from 43 patients in total were examined. Mucus was measured from 10 controls, 11 CRSsNP and 10 CRSwNP, and sinus tissue was measured from 10 controls, 15 CRSsNP and 10 CRSwNP. IL-8 and IFN-γ levels were outside of the detectable range of the assay. Levels of secreted IL-2, 4, 6, 10, and 17A correlated with tissue levels (P < 0.05 for all, r > 0.49) while TNF-α did not (P = 0.71). CRSsNP had elevated mucus levels of IL-2, 4, 6, 10, and 17A compared to controls. CRSwNP had elevated mucus levels of IL-4, 6, 10, 17A, and TNF-α compared to controls.

CONCLUSIONS

Cytokine levels in sinus secretions correlate with levels in sinus tissue and are elevated in CRS versus control based on Th1/Th2 skewing.

The immune network in pancreatic cancer development and progression

The presence of stromal desmoplasia is a hallmark of spontaneous pancreatic ductal adenocarcinoma, forming a unique microenvironment that comprises many cell types. Only recently, the immune system has entered the pathophysiology of pancreatic ductal adenocarcinoma development. Tumor cells in the pancreas seem to dysbalance the immune system, thus facilitating spontaneous cancer development. This review will try to assemble all relevant data to demonstrate the implications of the immune network on spontaneous cancer development.

STAT6 controls the number of regulatory T cells in vivo, thereby regulating allergic lung inflammation

STAT6 plays a central role in IL-4-mediated allergic responses. Several studies indicate that regulatory T cells (Tregs) can be modulated by IL-4 in vitro. We previously showed that STAT6(-/-) mice are highly resistant to allergic lung inflammation even when wild-type Th2 effectors were provided and that they have increased numbers of Tregs. However, the role of STAT6 in modulating Tregs in vivo during allergic lung inflammation has not been thoroughly investigated. To examine Treg and STAT6 interaction during allergic inflammation, STAT6(-/-), STAT6xRAG2(-/-), and RAG2(-/-) mice were subjected to OVA sensitization and challenge following adoptive transfer of OVA-specific, wild-type Th2 effectors with or without prior Treg depletion/inactivation, using anti-CD25 (PC61). As expected, STAT6(-/-) mice were highly resistant to airway inflammation and remodeling. In contrast, allergic lung inflammation was partially restored in STAT6(-/-) mice treated with PC61 to levels observed in STAT6xRAG2(-/-) mice. In some cases, STAT6xRAG2(-/-) mice were also given natural Tregs along with Th2 effectors. Adoptive transfer of natural Tregs caused a substantial reduction in bronchoalveolar lavage eosinophil composition and suppressed airway remodeling and T cell migration into the lung in STAT6xRAG2(-/-) mice to levels comparable to those in STAT6(-/-) mice. These results demonstrate the STAT6-dependent suppression of Tregs in vivo to promote allergic airway inflammation.

Dendritic cell expression of the signaling molecule TRAF6 is critical for gut microbiota-dependent immune tolerance

The intracellular signaling molecule TRAF6 is critical for Toll-like receptor (TLR)-mediated activation of dendritic cells (DCs). We now report that DC-specific deletion of TRAF6 (TRAF6ΔDC) resulted, unexpectedly, in loss of mucosal tolerance, characterized by spontaneous development of T helper 2 (Th2) cells in the lamina propria and eosinophilic enteritis and fibrosis in the small intestine. Loss of tolerance required the presence of gut commensal microbiota but was independent of DC-expressed MyD88. Further, TRAF6ΔDC mice exhibited decreased regulatory T (Treg) cell numbers in the small intestine and diminished induction of iTreg cells in response to model antigen. Evidence suggested that this defect was associated with diminished DC expression of interleukin-2 (IL-2). Finally, we demonstrate that aberrant Th2 cell-associated responses in TRAF6ΔDC mice could be mitigated via restoration of Treg cell activity. Collectively, our findings reveal a role for TRAF6 in directing DC maintenance of intestinal immune tolerance through balanced induction of Treg versus Th2 cell immunity.