Treg-specific IL-27Rα deletion uncovers a key role for IL-27 in Treg function to control autoimmunity.

Dysregulated Foxp3+ Treg functions result in uncontrolled immune activation and autoimmunity. Therefore, identifying cellular factors modulating Treg functions is an area of great importance. Here, using Treg-specific Il27ra-/- mice, we report that IL-27 signaling in Foxp3+ Tregs is essential for Tregs to control autoimmune inflammation in the central nervous system (CNS). Following experimental autoimmune encephalomyelitis (EAE) induction, Treg-specific Il27ra-/- mice develop more severe EAE. Consistent with the severe disease, the numbers of IFNγ- and IL-17-producing CD4 T cells infiltrating the CNS tissues are greater in these mice. Treg accumulation in the inflamed CNS tissues is not affected by the lack of IL-27 signaling in Tregs, suggesting a functional defect of Il27ra-/- Tregs. IL-10 production by conventional CD4 T cells and their CNS accumulation are rather elevated in Treg-specific Il27ra-/- mice. Analysis with Treg fate-mapping reporter mice further demonstrates that IL-27 signaling in Tregs may control stability of Foxp3 expression. Finally, systemic administration of recombinant IL-27 in Treg-specific Il27ra-/- mice fails to ameliorate the disease even in the presence of IL-27-responsive conventional CD4 T cells. These findings uncover a previously unknown role of IL-27 in regulating Treg function to control autoimmune inflammation.

Blockade of sustained tumor necrosis factor in a transgenic model of progressive autoimmune encephalomyelitis limits oligodendrocyte apoptosis and promotes oligodendrocyte maturation.

BACKGROUND: Tumor necrosis factor (TNF) is associated with several neurodegenerative disorders including multiple sclerosis (MS). Although TNF-targeted therapies have been largely unsuccessful in MS, recent preclinical data suggests selective soluble TNF inhibition can promote remyelination. This has renewed interest in regulation of TNF signaling in demyelinating disease, especially given the limited treatment options for progressive MS. Using a mouse model of progressive MS, this study evaluates the effects of sustained TNF on oligodendrocyte (OLG) apoptosis and OLG precursor cell (OPC) differentiation. METHODS: Induction of experimental autoimmune encephalomyelitis (EAE) in transgenic mice expressing a dominant-negative interferon-γ receptor under the human glial fibrillary acidic protein promoter (GFAPγR1Δ) causes severe non-remitting disease associated with sustained TNF. Therapeutic effects in GFAPγR1Δ mice treated with anti-TNF compared to control antibody during acute EAE were evaluated by assessing demyelinating lesion size, remyelination, OLG apoptosis, and OPC differentiation. RESULTS: More severe and enlarged demyelinating lesions in GFAPγR1Δ compared to wild-type (WT) mice were associated with increased OLG apoptosis and reduced differentiated CC1+Olig2+ OLG within lesions, as well as impaired upregulation of TNF receptor-2, suggesting impaired OPC differentiation. TNF blockade during acute EAE in GFAPγR1Δ both limited OLG apoptosis and enhanced OPC differentiation consistent with reduced lesion size and clinical recovery. TNF neutralization further limited increasing endothelin-1 (ET-1) expression in astrocytes and myeloid cells noted in lesions during disease progression in GFAPγR1Δ mice, supporting inhibitory effects of ET-1 on OPC maturation. CONCLUSION: Our data implicate that IFNγ signaling to astrocytes is essential to limit a detrimental positive feedback loop of TNF and ET-1 production, which increases OLG apoptosis and impairs OPC differentiation. Interference of this cycle by TNF blockade promotes repair independent of TNFR2 and supports selective TNF targeting to mitigate progressive forms of MS.

Sustained TNF production by central nervous system infiltrating macrophages promotes progressive autoimmune encephalomyelitis.

BACKGROUND: Tumor necrosis factor (TNF) has pleiotropic functions during both the demyelinating autoimmune disease multiple sclerosis (MS) and its murine model experimental autoimmune encephalomyelitis (EAE). How TNF regulates disability during progressive disease remains unresolved. Using a progressive EAE model characterized by sustained TNF and increasing morbidity, this study evaluates the role of unregulated TNF in exacerbating central nervous system (CNS) pathology and inflammation. METHODS: Progressive MS was mimicked by myelin oligodendrocyte glycoprotein (MOG) peptide immunization of mice expressing a dominant negative IFN-γ receptor alpha chain under the human glial fibrillary acidic protein promoter (GFAPγR1∆). Diseased GFAPγR1∆ mice were treated with anti-TNF or control monoclonal antibody during acute disease to monitor therapeutic effects on sustained disability, demyelination, CNS inflammation, and blood brain barrier (BBB) permeability. RESULTS: TNF was specifically sustained in infiltrating macrophages. Anti-TNF treatment decreased established clinical disability and mortality rate within 7 days. Control of disease progression was associated with a decline in myelin loss and leukocyte infiltration, as well as macrophage activation. In addition to mitigating CNS inflammation, TNF neutralization restored BBB integrity and enhanced CNS anti-inflammatory responses. CONCLUSIONS: Sustained TNF production by infiltrating macrophages associated with progressive EAE exacerbates disease severity by promoting inflammation and disruption of BBB integrity, thereby counteracting establishment of an anti-inflammatory environment required for disease remission.

Astrocyte response to IFN-γ limits IL-6-mediated microglia activation and progressive autoimmune encephalomyelitis.

BACKGROUND: Therapeutic modalities effective in patients with progressive forms of multiple sclerosis (MS) are limited. In a murine model of progressive MS, the sustained disability during the chronic phase of experimental autoimmune encephalomyelitis (EAE) correlated with elevated expression of interleukin (IL)-6, a cytokine with pleiotropic functions and therapeutic target for non-central nervous system (CNS) autoimmune disease. Sustained IL-6 expression in astrocytes restricted to areas of demyelination suggested that IL-6 plays a major role in disease progression during chronic EAE. METHODS: A progressive form of EAE was induced using transgenic mice expressing a dominant negative interferon-γ (IFN-γ) receptor alpha chain under control of human glial fibrillary acidic protein (GFAP) promoter (GFAPγR1Δ mice). The role of IL-6 in regulating progressive CNS autoimmunity was assessed by treating GFAPγR1Δ mice with anti-IL-6 neutralizing antibody during chronic EAE. RESULTS: IL-6 neutralization restricted disease progression and decreased disability, myelin loss, and axonal damage without affecting astrogliosis. IL-6 blockade reduced CNS inflammation by limiting inflammatory cell proliferation; however, the relative frequencies of CNS leukocyte infiltrates, including the Th1, Th17, and Treg CD4 T cell subsets, were not altered. IL-6 blockade rather limited the activation and proliferation of microglia, which correlated with higher expression of Galectin-1, a regulator of microglia activation expressed by astrocytes. CONCLUSIONS: These data demonstrate that astrocyte-derived IL-6 is a key mediator of progressive disease and support IL-6 blockade as a viable intervention strategy to combat progressive MS.

Magnesium decreases inflammatory cytokine production: a novel innate immunomodulatory mechanism.

MgSO(4) exposure before preterm birth is neuroprotective, reducing the risk of cerebral palsy and major motor dysfunction. Neonatal inflammatory cytokine levels correlate with neurologic outcome, leading us to assess the effect of MgSO(4) on cytokine production in humans. We found reduced maternal TNF-α and IL-6 production following in vivo MgSO(4) treatment. Short-term exposure to a clinically effective MgSO(4) concentration in vitro substantially reduced the frequency of neonatal monocytes producing TNF-α and IL-6 under constitutive and TLR-stimulated conditions, decreasing cytokine gene and protein expression, without influencing cell viability or phagocytic function. In summary, MgSO(4) reduced cytokine production in intrapartum women, term and preterm neonates, demonstrating effectiveness in those at risk for inflammation-associated adverse perinatal outcomes. By probing the mechanism of decreased cytokine production, we found that the immunomodulatory effect was mediated by magnesium and not the sulfate moiety, and it was reversible. Cellular magnesium content increased rapidly upon MgSO(4) exposure, and reduced cytokine production occurred following stimulation with different TLR ligands as well as when magnesium was added after TLR stimulation, strongly suggesting that magnesium acts intracellularly. Magnesium increased basal IĸBα levels, and upon TLR stimulation was associated with reduced NF-κB activation and nuclear localization. These findings establish a new paradigm for innate immunoregulation, whereby magnesium plays a critical regulatory role in NF-κB activation, cytokine production, and disease pathogenesis.

Multipotent adult progenitor cells induce regulatory T cells and promote their suppressive phenotype via TGFß and monocyte-dependent mechanisms.

Dysregulation of the immune system can initiate chronic inflammatory responses that exacerbate disease pathology. Multipotent adult progenitor cells (MAPC cells), an adult adherent bone-marrow derived stromal cell, have been observed to promote the resolution of uncontrolled inflammatory responses in a variety of clinical conditions including acute ischemic stroke, acute myocardial infarction (AMI), graft vs host disease (GvHD), and acute respiratory distress syndrome (ARDS). One of the proposed mechanisms by which MAPC cells modulate immune responses is via the induction of regulatory T cells (Tregs), however, the mechanism(s) involved remains to be fully elucidated. Herein, we demonstrate that, in an in vitro setting, MAPC cells increase Treg frequencies by promoting Treg proliferation and CD4+ T cell differentiation into Tregs. Moreover, MAPC cell-induced Tregs (miTregs) have a more suppressive phenotype characterized by increased expression of CTLA-4, HLA-DR, and PD-L1 and T cell suppression capacity. MAPC cells also promoted Treg activation by inducing CD45RA+ CD45RO+ transitional Tregs. Additionally, we identify transforming growth factor beta (TGFß) as an essential factor for Treg induction secreted by MAPC cells. Furthermore, inhibition of indoleamine 2, 3-dioxygenase (IDO) resulted in decreased Treg induction by MAPC cells demonstrating IDO involvement. Our studies also show that CD14+ monocytes play a critical role in Treg induction by MAPC cells. Our study describes MAPC cell dependent Treg phenotypic changes and provides evidence of potential mechanisms by which MAPC cells promote Treg differentiation.

Augmented Expansion of Treg Cells From Healthy and Autoimmune Subjects via Adult Progenitor Cell Co-Culture.

Recent clinical experience has demonstrated that adoptive regulatory T (Treg) cell therapy is a safe and feasible strategy to suppress immunopathology via induction of host tolerance to allo- and autoantigens. However, clinical trials continue to be compromised due to an inability to manufacture a sufficient Treg cell dose. Multipotent adult progenitor cells (MAPCⓇ) promote Treg cell differentiation in vitro, suggesting they may be repurposed to enhance ex vivo expansion of Tregs for adoptive cellular therapy. Here, we use a Good Manufacturing Practice (GMP) compatible Treg expansion platform to demonstrate that MAPC cell-co-cultured Tregs (MulTreg) exhibit a log-fold increase in yield across two independent cohorts, reducing time to target dose by an average of 30%. Enhanced expansion is coupled to a distinct Treg cell-intrinsic transcriptional program characterized by elevated expression of replication-related genes (CDK1, PLK1, CDC20), downregulation of progenitor and lymph node-homing molecules (LEF1 CCR7, SELL) and induction of intestinal and inflammatory tissue migratory markers (ITGA4, CXCR1) consistent with expression of a gut homing (CCR7lo ß7hi) phenotype. Importantly, we find that MulTreg are more readily expanded from patients with autoimmune disease compared to matched Treg lines, suggesting clinical utility in gut and/or T helper type1 (Th1)-driven pathology associated with autoimmunity or transplantation. Relative to expanded Tregs, MulTreg retain equivalent and robust purity, FoxP3 Treg-Specific Demethylated Region (TSDR) demethylation, nominal effector cytokine production and potent suppression of Th1-driven antigen specific and polyclonal responses in vitro and xeno Graft vs Host Disease (xGvHD) in vivo. These data support the use of MAPC cell co-culture in adoptive Treg therapy platforms as a means to rescue expansion failure and reduce the time required to manufacture a stable, potently suppressive product.

Bidirectional NK/DC interactions promote CD4 expression on NK cells, DC maturation, and HIV infection.

Interactions between natural killer (NK) and dendritic cells (DCs) are integral to immune response development, potentially leading to bidirectional NK/DC activation. We demonstrate that autologous NK/DC interactions induce CD4 expression on NK cells, influencing degranulation. Cell contact is required, with high NK:DC ratios and mature DCs most effectively inducing CD4 expression. CD4(+) NK cells, in turn, mediate DC maturation via contact-dependent and independent pathways, more effectively maturing DCs than CD4(-) NK cells. Bidirectional NK/DC interactions also impact HIV infection, as NK-matured DCs effectively deliver infectious HIV to T cells, via trans-infection. DC-induced CD4 expression also renders NK cells susceptible to HIV infection. Focusing on NK/DC interactions, DCs can transfer infectious virus and enhance HIV infection of CD4(+) NK cells, strongly suggesting that these interactions influence HIV pathogenesis. Findings provide new insight regarding NK/DC interactions, defining a mechanism by which cellular interactions in the absence of pathogens promote DC-mediated amplification of HIV infection.

Impaired induction of CD27 and CD28 predicts naive CD4 T cell proliferation defects in HIV disease.

Many immunological defects have been described in HIV disease, including a diminished capacity of naive CD4+ T cells to expand after TCR stimulation. The mechanisms underlying impaired naive CD4+ T cell expansion in HIV disease are not well described. Using a rigorous phenotypic definition of naive T cells, we found that cell cycle entry after TCR engagement was restricted to cells that increased surface expression of costimulatory molecules CD27 and CD28. Induction of these receptors, however, was not sufficient to result in cell cycle entry among the CD4+CD31- naive T cell subset. Analyses of cells from HIV-infected persons indicated that naive CD4+CD31+ T cells from these subjects were impaired in their ability to enter the cell cycle after stimulation and this impairment was predicted by the relatively poor induction of costimulatory molecules on these cells. Thus, failure to increase surface expression of costimulatory molecules may contribute to the naive T cell expansion failure that characterizes HIV infection.