Splenic Counterparts Research Articles

Synthesis and Detection of BODIPY‐, Biotin‐, and 19F‐ Labeled Single‐Entity Dendritic Heparan Sulfate Mimetics

AbstractHeparin and heparan sulfate (HS) are naturally occurring mammalian glycosaminoglycans, and their synthetic and semi‐synthetic mimetics have attracted significant interest as potential therapeutics. However, understanding the mechanism of action by which HS, heparin, and HS mimetics have a biological effect is difficult due to their highly charged nature, broad protein interactomes, and variable structures. To address this, a library of novel single‐entity dendritic mimetics conjugated to BODIPY, Fluorine‐19 (19F), and biotin was synthesized for imaging and localization studies. The novel dendritic scaffold allowed for the conjugation of labeling moieties without reducing the number of sulfated capping groups, thereby better mimicking the multivalent nature of HS‐protein interactions. The 19F labeled mimetics were assessed in phantom studies and were detected at concentrations as low as 5 mM. Flow cytometric studies using a fluorescently labeled mimetic showed that the compound associated with immune cells from tumors more readily than splenic counterparts and was directed to endosomal‐lysosomal compartments within immune cells and cancer cells. Furthermore, the fluorescently labeled mimetic entered the central nervous system and was detectable in brain‐infiltrating immune cells 24 hours after treatment. Here, we report the enabling methodology for rapidly preparing various labeled HS mimetics and molecular probes with diverse potential therapeutic applications.

Synthesis and Detection of BODIPY-, Biotin-, and 19 F- Labeled Single-Entity Dendritic Heparan Sulfate Mimetics.

Heparin and heparan sulfate (HS) are naturally occurring mammalian glycosaminoglycans, and their synthetic and semi-synthetic mimetics have attracted significant interest as potential therapeutics. However, understanding the mechanism of action by which HS, heparin, and HS mimetics have a biological effect is difficult due to their highly charged nature, broad protein interactomes, and variable structures. To address this, a library of novel single-entity dendritic mimetics conjugated to BODIPY, Fluorine-19 (19 F), and biotin was synthesized for imaging and localization studies. The novel dendritic scaffold allowed for the conjugation of labeling moieties without reducing the number of sulfated capping groups, thereby better mimicking the multivalent nature of HS-protein interactions. The 19 F labeled mimetics were assessed in phantom studies and were detected at concentrations as low as 5 mM. Flow cytometric studies using a fluorescently labeled mimetic showed that the compound associated with immune cells from tumors more readily than splenic counterparts and was directed to endosomal-lysosomal compartments within immune cells and cancer cells. Furthermore, the fluorescently labeled mimetic entered the central nervous system and was detectable in brain-infiltrating immune cells 24 hours after treatment. Here, we report the enabling methodology for rapidly preparing various labeled HS mimetics and molecular probes with diverse potential therapeutic applications.

Bone Marrow Harbors a Unique Population of Dendritic Cells with the Potential to Boost Neutrophil Formation upon Exposure to Fungal Antigen.

Apart from controlling hematopoiesis, the bone marrow (BM) also serves as a secondary lymphoid organ, as it can induce naïve T cell priming by resident dendritic cells (DC). When analyzing DCs in murine BM, we uncovered that they are localized around sinusoids, can (cross)-present antigens, become activated upon intravenous LPS-injection, and for the most part belong to the cDC2 subtype which is associated with Th2/Th17 immunity. Gene-expression profiling revealed that BM-resident DCs are enriched for several c-type lectins, including Dectin-1, which can bind beta-glucans expressed on fungi and yeast. Indeed, DCs in BM were much more efficient in phagocytosis of both yeast-derived zymosan-particles and Aspergillus conidiae than their splenic counterparts, which was highly dependent on Dectin-1. DCs in human BM could also phagocytose zymosan, which was dependent on β1-integrins. Moreover, zymosan-stimulated BM-resident DCs enhanced the differentiation of hematopoietic stem and progenitor cells towards neutrophils, while also boosting the maintenance of these progenitors. Our findings signify an important role for BM DCs as translators between infection and hematopoiesis, particularly in anti-fungal immunity. The ability of BM-resident DCs to boost neutrophil formation is relevant from a clinical perspective and contributes to our understanding of the increased susceptibility for fungal infections following BM damage.

The downregulation of IL-18R defines bona fide kidney-resident CD8+ Tcells.

SummaryStepwise induction of CD69 and CD103 marks distinct differentiation stages of mucosal Trms. But the majority of non-mucosal Trm lacks CD103 expression. The expression of CD69 alone cannot faithfully define Trm cells in heavily vascularized non-mucosal tissues, such as the kidney. Here, we found that a subset of kidney Trms downregulated IL-18 receptor during differentiation. Via global transcriptional analysis and parabiosis experiments, we have discovered that the downregulation of interleukin-18 receptor (IL-18R) is associated with the establishment of tissue residency. Together with the expression of CD69, IL-18Rlo exclusively identify tissue-resident cells whereas IL-18Rhi population contains both tissue-resident and migratory ones. Local cytokines including transforming growth factor β (TGF-β) and interferon α (IFN-α)/β as well as TGF-β-dependent suppression of transcription factor Tcf-1 are essential for IL-18R downregulation during kidney Trm differentiation. Together, we identified a convenient surface marker to distinguish bona fide kidney-resident CD8+ T cells as well as underlying molecular mechanisms controlling this differentiation process.

Abstract PR16: RNA aptamers specific for tumor-infiltrating myeloid cells

Abstract Myeloid cells have been extensively studied in the tumor microenvironment for their role in promoting cancer cell survival and metastases. However, their peculiar activated phenotype has not been exploited for the targeted delivery of anticancer agents to the tumor site. Here we report a new therapeutic strategy that allows the delivery of cancer drugs to both tumor and metastases by the preferential targeting of genetically stable tumor-infiltrating myeloid cells (TIMC). We identified 4 monoclonal RNA aptamers that specifically recognize myeloid-derived suppressor cells (MDSC) and macrophages infiltrating the tumor, but not the splenic counterparts. The use of these aptamers conjugated to doxorubicin greatly enhances the accumulation of the chemotherapeutic drug in the primary and metastatic tumor sites in multiple cancer models. Compared to their individual components or current therapeutic approaches, doxorubicin-conjugated TIMC-specific aptamers show enhanced anticancer efficacy and no detectable treatment-related toxicity. This strategy has the intrinsic potential to target multiple tumor types through the same reagents. This abstract is also being presented as Poster A35. Citation Format: Adriana De La Fuente, Jimmy Caroli, Dimitri Van Simaeys, Serena Zilio, Emilia Mazza, Vincenzo Bronte, Silvio Bicciato, Paolo Serafini. RNA aptamers specific for tumor-infiltrating myeloid cells [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr PR16.

ATP-degrading ENPP1 is required for survival (or persistence) of long-lived plasma cells

Survival of antibody-secreting plasma cells (PCs) is vital for sustained antibody production. However, it remains poorly understood how long-lived PCs (LLPCs) are generated and maintained. Here we report that ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) is preferentially upregulated in bone marrow LLPCs compared with their splenic short-lived counterparts (SLPCs). We studied ENPP1-deficient mice (Enpp1−/−) to determine how the enzyme affects PC biology. Although Enpp1−/− mice generated normal levels of germinal center B cells and plasmablasts in periphery, they produced significantly reduced numbers of LLPCs following immunization with T-dependent antigens or infection with plasmodium C. chabaudi. Bone marrow chimeric mice showed B cell intrinsic effect of ENPP1 selectively on generation of bone marrow as well as splenic LLPCs. Moreover, Enpp1−/− PCs took up less glucose and had lower levels of glycolysis than those of wild-type controls. Thus, ENPP1 deficiency confers an energetic disadvantage to PCs for long-term survival and antibody production.

Bone marrow T cells populations are differently affected by sepsis than their splenic counterparts in the murine sepsis cecal ligation and puncture (CLP) model

Abstract Sepsis is known to induce lymphopenia which correlates with secondary infections and mortality. In sepsis survivors the lymphocyte count restores with time, although the T cell responses are impaired. So far, the mechanisms of T cells recovery are not fully understood and the murine studies were focused on the peripheral lymphatic organs in which the spleen was most common. Our study was designed to elucidate the recovery of bone marrow (BM) T cells which contain population of memory cells, after the CLP murine sepsis. In our model, mild CLP produced peripheral lymphopenia which was lowest at 48h after CLP but after 7 days circulating T cells count was rebounding. 7 days after CLP the BM frequencies of naïve and central memory (CD44+CD62L+) CD4 cells were unchanged while they were reduced in the spleen. Percentage of effector memory (CD44+CD62L−) CD4 and CD8 cells increased in the BM and at the same time they dramatically decreased in the spleen. On the contrary, the effector (CD44−CD62L+) CD4 and CD8 cells expanded at that time point in the spleen while they did not change in the BM. At D7 after CLP, the rates of BrdU+ proliferating CD4+ and CD8+ cells were markedly higher in the BM than spleen. Among the BM CD4+ cells most of the proliferating cells were the effector memory cells, while the effector CD4+ had highest proliferation rate in the spleen. Similarly, CD8 effector memory cells in the BM and CD8 effector cells were most extensively proliferating in the BM and the spleen, respectively. Taken together, our data point to the BM as the place of effector memory T cell proliferation during post-sepsis recovery.

Parasite-Specific CD4+ IFN-γ+ IL-10+ T Cells Distribute within Both Lymphoid and Nonlymphoid Compartments and Are Controlled Systemically by Interleukin-27 and ICOS during Blood-Stage Malaria Infection.

Immune-mediated pathology in interleukin-10 (IL-10)-deficient mice during blood-stage malaria infection typically manifests in nonlymphoid organs, such as the liver and lung. Thus, it is critical to define the cellular sources of IL-10 in these sensitive nonlymphoid compartments during infection. Moreover, it is important to determine if IL-10 production is controlled through conserved or disparate molecular programs in distinct anatomical locations during malaria infection, as this may enable spatiotemporal tuning of the regulatory immune response. In this study, using dual gamma interferon (IFN-γ)–yellow fluorescent protein (YFP) and IL-10–green fluorescent protein (GFP) reporter mice, we show that CD4+ YFP+ T cells are the major source of IL-10 in both lymphoid and nonlymphoid compartments throughout the course of blood-stage Plasmodium yoelii infection. Mature splenic CD4+ YFP+ GFP+ T cells, which preferentially expressed high levels of CCR5, were capable of migrating to and seeding the nonlymphoid tissues, indicating that the systemically distributed host-protective cells have a common developmental history. Despite exhibiting comparable phenotypes, CD4+ YFP+ GFP+ T cells from the liver and lung produced significantly larger quantities of IL-10 than their splenic counterparts, showing that the CD4+ YFP+ GFP+ T cells exert graded functions in distinct tissue locations during infection. Unexpectedly, given the unique environmental conditions within discrete nonlymphoid and lymphoid organs, we show that IL-10 production by CD4+ YFP+ T cells is controlled systemically during malaria infection through IL-27 receptor signaling that is supported after CD4+ T cell priming by ICOS signaling. The results in this study substantially improve our understanding of the systemic IL-10 response to malaria infection, particularly within sensitive nonlymphoid organs.

Identification and Analysis of Natural Killer Cells in Murine Nasal Passages.

BackgroundNatural killer (NK) cells in the upper respiratory airways are not well characterized. In the current study, we sought to characterize and functionally assess murine nasal NK cells.MethodsUsing immunohistochemistry and flow cytometry, we compared the nasal NK cells of Ncr1 GFP/+ knock-in mice, whose NK cells produced green fluorescent protein, with their splenic and pulmonary counterparts. In addition, we functionally analyzed the nasal NK cells of these mice in vitro. To assess the in vivo functions of nasal NK cells, C57BL/6 mice depleted of NK cells after treatment with PK136 antibody were nasally infected with influenza virus PR8.ResultsImmunohistochemical analysis confirmed the presence of NK cells in the lamina propria of nasal mucosa, and flow cytometry showed that these cells were of NK cell lineage. The expression patterns of Ly49 receptor, CD11b/CD27, CD62L and CD69 revealed that nasal NK cells had an immature and activated phenotype compared with that of their splenic and pulmonary counterparts. Effector functions including degranulation and IFN(interferon)-γ production after in vitro stimulation with phorbol 12-myristate-13-acetate plus ionomycin or IL(interleukin)-12 plus IL-18 were dampened in nasal NK cells, and the depletion of NK cells led to an increased influenza virus titer in nasal passages.ConclusionsThe NK cells of the murine nasal passage belong to the conventional NK cell linage and characteristically demonstrate an immature and activated phenotype. Despite their hyporesponsiveness in vitro, nasal NK cells play important roles in the host defense against nasal influenza virus infection.

The omentum is a site of protective IgM production during intracellular bacterial infection.

Infection of mice with the bacterium Ehrlichia muris elicits a protective T cell-independent (TI) IgM response mediated primarily by a population of CD11c-expressing plasmablasts in the spleen. Although splenic marginal zone (MZ) B cells are considered to be important for TI responses to blood-borne pathogens, MZ B cells were not responsible for generating plasmablasts in response to Ehrlichia muris. Moreover, antigen-specific serum IgM was decreased only modestly in splenectomized mice and in mice that lacked spleen, lymph nodes, and Peyer's patches (SLP mice). Both splenectomized and SLP mice were protected against lethal ehrlichial challenge infection. Moreover, we found a high frequency of Ehrlichia-specific plasmablasts in the omentum of both conventional and SLP mice. Omental plasmablasts elicited during Ehrlichia infection lacked expression of CD138 but expressed CD11c in a manner similar to that of their splenic counterparts. Selective ablation of CD11c-expressing B cells nearly eliminated the omental Ehrlichia-specific plasmablasts and reduced antigen-specific serum IgM, identifying the omental B cells as a source of IgM production in the SLP mice. Generation of the omental plasmablasts was route dependent, as they were detected following peritoneal infection but not following intravenous infection. Our data identify the omentum as an important auxiliary site of IgM production during intracellular bacterial infection.

Antigen dependently activated cluster of differentiation 8-positive T cells cause perforin-mediated neurotoxicity in experimental stroke.

Neuroinflammation plays a key role in secondary brain damage after stroke. Although deleterious effects of proinflammatory cytokines are well characterized, direct cytotoxic effects of invading immune cells on the ischemic brain and the importance of their antigen-dependent activation are essentially unknown. Here we examined the effects of adaptive and innate immune cells-cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells-that share the direct perforin-mediated cytotoxic pathway on outcome after cerebral ischemia in mice. Although CTLs and NK cells both invaded the ischemic brain, only brain-infiltrating CTLs but not NK cells were more activated than their splenic counterparts. Depletion of CTLs decreased infarct volumes and behavioral deficit in two ischemia models, whereas NK cell depletion had no effect. Correspondingly, adoptive CTL transfer from wild-type into Rag1 knock-out mice increased infarct size. Adoptive CTL transfer from perforin knock-out or interferon-γ knock-out mice into Rag1 knock-out mice revealed that CTL neurotoxicity was mediated by perforin. Accordingly, CTLs isolated from wild-type or interferon-γ knock-out but not from perforin knock-out mice induced neuronal cell death in vitro. CTLs derived from ovalbumin-specific T-cell receptor transgenic mice were not activated and infiltrated less into the ischemic brain compared with wild-type CTLs. Their transfer did not increase the infarct size of Rag1 knock-out mice, indicating antigen-dependent activation as an essential component of CTL neurotoxicity. Our findings underscore the importance of antigen-dependent, direct cytotoxic immune responses in stroke and suggest modulation of CTLs and their effector pathways as a potential new strategy for stroke therapy.

Tissue-resident exhausted effector memory CD8+ T cells accumulate in the retina during chronic experimental autoimmune uveoretinitis.

Experimental autoimmune uveoretinitis is a model for noninfectious posterior segment intraocular inflammation in humans. Although this disease is CD4+ T cell dependent, in the persistent phase of disease CD8+ T cells accumulate. We show that these are effector memory CD8+ T cells that differ from their splenic counterparts with respect to surface expression of CD69, CD103, and Ly6C. These retinal effector memory CD8+ T cells have limited cytotoxic effector function, are impaired in their ability to proliferate in response to Ag-specific stimulation, and upregulate programmed death 1 receptor. Treatment with fingolimod (FTY720) during the late phase of disease revealed that retinal CD8+ T cells were tissue resident. Despite signs of exhaustion, these cells were functional, as their depletion resulted in an expansion of retinal CD4+ T cells and CD11b+ macrophages. These results demonstrate that, during chronic autoimmune inflammation, exhausted CD8+ T cells become established in the local tissue. They are phenotypically distinct from peripheral CD8+ T cells and provide local signals within the tissue by expression of inhibitory receptors such as programmed death 1 that limit persistent inflammation.

Oral infection drives a distinct population of resident memory CD8 T cells with enhanced protective function (LYM4P.751)

Abstract The intestinal mucosa is designed for promoting specialized T cell responses which are distinct from responses generated systemically or even from other mucosal surfaces. Oral infection with Listeria monocytogenes induced a robust CD8 T cell response. Unlike splenic short-lived effector cells (SLEC) early after infection, intestinal SLEC rapidly underwent apoptosis resulting in a predominant memory precursor (MPEC) population between 9 and 12 dpi. Similarly, the resulting IEL population was functionally superior to their splenic counterparts and provided rapid protection upon secondary oral challenge. These early memory cells, but not other effector cell subsets, rapidly upregulated CD103 identifying them as mucosal resident memory precursors. Surprisingly, CD103 expression promoted T cell accumulation in the epithelium but did not regulate long term retention within the epithelial layer or CD8 T cell fate. Indeed, intranasal or intravenous Listeria monocytogenes infection generated memory CD8 T cell populations within the intestinal epithelial compartment which were heterogeneous for CD103 expression and displayed distinct effector cell subsets. Collectively, this data demonstrates the importance of priming location for generating intestinal resident and protective T cell memory and demonstrates that priming location and tissue of residence impacts resident memory T cell formation and maintenance.

CD39 expression by hepatic myeloid dendritic cells attenuates inflammation in liver transplant ischemia-reperfusion injury in mice

Hepatic innate immune cells, in particular, interstitial dendritic cells (DCs), regulate inflammatory responses and may promote inherent liver tolerogenicity. After tissue injury, adenosine triphosphate (ATP) is released and acts as a damage-associated molecular pattern that activates innate immune cells by pattern recognition receptors. CD39 (ectonucleoside triphosphate diphosphohydrolase-1) rapidly hydrolyzes extracellular ATP to maintain physiological levels. We hypothesized that CD39 expression on liver DCs might contribute to regulation of their innate immune functions. Mouse liver conventional myeloid DCs (mDCs) were hyporesponsive to ATP, compared with their splenic counterparts. This disparity was ascribed to more efficient hydrolysis of ATP by higher expression of CD39 on liver mDCs. Human liver mDCs expressed greater levels of CD39 than those from peripheral blood. The comparatively high expression of CD39 on liver mDCs correlated strongly with both ATP hydrolysis and adenosine production. Notably, CD39(-/-) mouse liver mDCs exhibited a more mature phenotype, greater responsiveness to Toll-like receptor 4 ligation, and stronger proinflammatory and immunostimulatory activity than wild-type (WT) liver mDCs. To investigate the role of CD39 on liver mDCs in vivo, we performed orthotopic liver transplantation with extended cold preservation using CD39(-/-) or WT donor mouse livers. Compared to WT liver grafts, CD39(-/-) grafts exhibited enhanced interstitial DC activation, elevated proinflammatory cytokine levels, and more-severe tissue injury. Moreover, portal venous delivery of WT, but not CD39(-/-) liver mDCs, to donor livers immediately post-transplant exerted a protective effect against graft injury in CD39(-/-) to CD39(-/-) liver transplantation. These data reveal that CD39 expression on conventional liver mDCs limits their proinflammatory activity and confers protective properties on these important innate immune cells against liver transplant ischemia/reperfusion injury.

CCL22-Producing CD8α− Myeloid Dendritic Cells Mediate Regulatory T Cell Recruitment in Response to G-CSF Treatment

G-CSF prevents type 1 diabetes in the NOD mouse by promoting the local recruitment of T regulatory cells (Tregs). This is an indirect effect because adoptive transfer of G-CSF-induced tolerogenic dendritic cells (DCs) promotes Treg accumulation. However, the identity of the particular DC subset and the molecule(s) mediating this effect remain unknown. We demonstrate in this study that the adoptive transfer of CD11c(high)CD8α(-) DCs isolated from pegylated G-CSF (pegG-CSF) recipients, but not that of other DC subtypes, enhanced the pancreatic recruitment of CD4(+)CD25(+)Foxp3(+) Tregs, which generated increased amounts of TGF-β. Likewise, only CD11c(high)CD8α(-) DCs from pegG-CSF recipients secreted the chemokine CCL22 at levels that effectively attracted Tregs. PegG-CSF was more efficient at enhancing the synthesis of CCL22 by CD11c(high)CD8α(-) DCs from the pancreatic lymph nodes compared with those from the spleen. Accordingly, CD11c(high)CD8α(-) DCs from the pancreatic lymph nodes of pegG-CSF recipients were more efficient than their splenic counterparts in the recruitment of Tregs upon adoptive transfer. Predictably, CD11c(high)CD8α(-) DCs failed to recruit these Tregs both in vivo and in vitro following intracellular neutralization of CCL22. These data assign a key role to CD8α(-) DCs and CCL22 in Treg recruitment in the protection of NOD mice against type 1 diabetes following the treatment with G-CSF.

Distinct LLO-specific CD4 T cells infiltrate the intestinal mucosa following oral Listeria monocytogenes infection. (P3224)

Abstract Listeria monocytogenes (LM) is an enteroinvasive pathogen and the cause of listeriosis, a highly fatal foodborne infection. Using an oral LM infection model, we show that a subset of blood-borne listeriolysin O (LLO)-specific CD4 T cells transiently expressed the α4β7 integrin early after infection. Antigen-specific CD4 T cells rapidly accumulated in the mucosa and mounted a robust recall response following secondary infection. On day 9 post LM infection, LLO-specific CD4 T cells in the mucosa are almost exclusively Ly6Clow/CD27low and this population persists throughout memory. In contrast, LLO-specific CD4 T cells isolated from the spleen and MLN were heterogenous for CD27 and Ly6C expression. Mucosal LLO-specific CD27lowLy6ClowCD4 T cells produced IFN-γ and IL-2 and a small subset also produced IL-17. Interestingly, IL-17 production increased in mucosal memory CD4 T cells. Furthermore, IL-17 production was increased in mucosal CD4 T cells in CD69-deficient mice. However, mixed bone marrow chimera studies indicated that this phenomenon is independent ofCD69 expression on responding CD4 T cells. Depletion of CD4 T cells during memory led to higher bacterial burden in the gut and spleen. These results indicate that mucosal effector and memory CD4 T cells are phenotypically and functionally distinct from their splenic counterparts. Thus, our findings demonstrate an important role for mucosal memory CD4 T cells in protection against oral infection.

Intrahepatic Infiltrating NK and CD8 T Cells Cause Liver Cell Death in Different Phases of Dengue Virus Infection

Elevated liver enzyme level is an outstanding feature in patients with dengue. However, the pathogenic mechanism of liver injury has not been clearly demonstrated. In this study, employing a mouse model we aimed to investigate the immunopathogenic mechanism of dengue liver injury. Immunocompetent C57BL/6 mice were infected intravenously with dengue virus strain 16681. Infected mice had transient viremia, detectable viral capsid gene and cleaved caspase 3 in the liver. In the mean time, NK cell and T cell infiltrations peaked at days 1 and 5, respectively. Neutralizing CXCL10 or depletion of Asialo GM1+ cells reduced cleaved caspase 3 and TUNEL+ cells in the liver at day 1 after infection. CD8+ T cells infiltrated into the liver at later time point and at which time intrahepatic leukocytes (IHL) exhibited cytotoxicity against DENV-infected targets. Cleaved caspase 3 and TUNEL+ cells were diminished in mice with TCRβ deficiency and in those depleted of CD8+ T cells, respectively, at day 5 after infection. Moreover, intrahepatic CD8+ T cells were like their splenic counterparts recognized DENV NS4B99–107 peptide. Together, these results show that infiltrating NK and CD8+ T cells cause liver cell death. While NK cells were responsible for cell death at early time point of infection, CD8+ T cells were for later. CD8+ T cells that recognize NS4B99–107 constitute at least one of the major intrahepatic cytotoxic CD8+ T cell populations.

Foxp3+Treg cells in the inflamed CNS are insensitive to IL‐6‐driven IL‐17 production

Foxp3(+) T regulatory (Treg) cells can be induced to produce interleukin (IL)-17 by in vitro exposure to proinflammatory cytokines, drawing into question their functional stability at sites of inflammation. Unlike their splenic counterparts, Treg cells from the inflamed central nervous system (CNS-Treg cells) during EAE resisted conversion to IL-17 production when exposed to IL-6. We show that the highly activated phenotype of CNS-Treg cells includes elevated expression of the Th1-associated molecules CXCR3 and T-bet, but reduced expression of the IL-6 receptor α chain (CD126) and the signaling chain gp130. We found a lack of IL-6 receptor on all CNS CD4(+) T cells, which was reflected by an absence of both classical and trans-IL-6 signaling in CNS CD4(+) cells, compared with their splenic counterparts. We propose that extinguished responsiveness to IL-6 (via down-regulation of CD126 and gp130) stabilizes the regulatory phenotype of activated Treg cells at sites of autoimmune inflammation.

Systemic IL-12 Administration Alters Hepatic Dendritic Cell Stimulation Capabilities

The liver is an immunologically unique organ containing tolerogenic dendritic cells (DC) that maintain an immunosuppressive microenvironment. Although systemic IL-12 administration can improve responses to tumors, the effects of IL-12-based treatments on DC, in particular hepatic DC, remain incompletely understood. In this study, we demonstrate systemic IL-12 administration induces a 2–3 fold increase in conventional, but not plasmacytoid, DC subsets in the liver. Following IL-12 administration, hepatic DC became more phenotypically and functionally mature, resembling the function of splenic DC, but differed as compared to their splenic counterparts in the production of IL-12 following co-stimulation with toll-like receptor (TLR) agonists. Hepatic DCs from IL-12 treated mice acquired enhanced T cell proliferative capabilities similar to levels observed using splenic DCs. Furthermore, IL-12 administration preferentially increased hepatic T cell activation and IFNγ expression in the RENCA mouse model of renal cell carcinoma. Collectively, the data shows systemic IL-12 administration enables hepatic DCs to overcome at least some aspects of the inherently suppressive milieu of the hepatic environment that could have important implications for the design of IL-12-based immunotherapeutic strategies targeting hepatic malignancies and infections.

Naïve CD4+ T cells of Peyer's patches produce more IL-6 than those of spleen in response to antigenic stimulation

Peyer's patches (PPs) are potential sites where specific mucosal immune responses and oral tolerance are induced. The unique features of these immune responses are thought to occur in micromilieu and are largely affected by antigen-presenting cells (APCs) such as dendritic cells. In this study, we investigated the cytokine profiles induced by the activation of CD4+ T cells of PPs. PP cells from TCR transgenic mice secreted greater amounts of IL-5 and IL-6 than spleen cells after antigenic stimulation. IL-5 was mainly produced by PP non-T cells, whereas IL-6 was secreted by PP CD4+ cells. PPs contained two major populations including naïve and memory/activated CD4+ cells; both populations secreted IL-6 upon activation. We also found that CD4+/CD62Lhi naïve cells from PPs secreted a greater amount of IL-6 after stimulation than those from the spleen. Furthermore, subtraction and qPCR analyses revealed that PP CD4+/CD62Lhi cells express a greater amount of transcripts of GA-binding protein β subunit 1 than those of the spleen. These results suggest that naïve T cells as well as non-T cells and activated/memory T cells from PPs are distinct from their splenic counterparts and thus cause unique immune responses the in intestine.