Thursday, August 25, 2011

Hot off the presses! Aug 26 Immunity

The Aug 26 issue of the Immunity is now up on Pubget (About Immunity): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

  • Baruj Benacerraf (1921–2011)
    - Immunity 35(2):147-148 (2011)
  • Taking the STING Out of Malaria
    - Immunity 35(2):149-151 (2011)
    The innate immune response to malaria is a major determinant of disease severity and outcome. In this issue of Immunity, Sharma et al. (2011) provide evidence of a unique DNA sensing pathway that may contribute to immunopathology in plasmodial infections.
  • A New Vampire Saga: The Molecular Mechanism of T Cell Trogocytosis
    - Immunity 35(2):151-153 (2011)
    In the current issue of Immunity, Martínez-Martín et al. (2011) describe the central supramolecular activation cluster (cSMAC) as a site of clathrin-independent T cell receptor (TCR) internalization and trogocytosis. Further, they identify small Rho GTPases TC21 and RhoG as key mediators of these processes.
  • Intracellular Pathogens and CD8+ Dendritic Cells: Dangerous Liaisons
    - Immunity 35(2):153-155 (2011)
    CD8+ dendritic cells comprise a distinct cell type whose function is unclear. In this issue of Immunity, Mashayekhi et al. (2011) show these cells are essential for protection against the parasite Toxoplasma, but Edelson et al. (2011) show they are hijacked by Listeria during initial spreading.
  • Value Added: Neural Progenitor Cells Suppress Inflammation and Autoimmunity
    - Immunity 35(2):156-157 (2011)
    Neural progenitor cells (NPCs) can repair damaged myelin in neurodegenerative diseases. In this issue of Immunity, Cao et al. (2011) report that NPCs also produce the cytokine LIF, which suppresses Th17 cell-driven inflammation and autoimmunity by upregulating the protein Socs3.
  • When the Going Gets Tough, Memory T Cells Check Out
    - Immunity 35(2):158-160 (2011)
    Memory CD8+ T cells proliferate faster than naive cells to rapidly control an infectious challenge, but West et al. (2011) in this issue of Immunity report that this superiority is lost in the face of a high dose or chronic viral challenge.
  • CD8+ T Cells: Foot Soldiers of the Immune System
    - Immunity 35(2):161-168 (2011)
    Resting naive CD8+ T cells have an astounding capacity to react to pathogens by massive expansion and differentiation into cytotoxic effector cells that migrate to all corners of the body to clear the infection. The initial interaction with antigen-presenting cells in the central lymphoid organs drives an orchestrated program of differentiation aimed at producing sufficient numbers of effectors to get the job done without resulting in clonal exhaustion. Interactions with antigen-presenting cells and other immune cells continue at the site of infection to regulate further on-site expansion and differentiation, all with the goal of protecting the host with minimal bystander tissue damage. Here we review recent advances in CD8+ T cell recognition of antigen in lymphoid as well as in nonlymphoid tissues in the periphery, and how CD8+ T cell expansion and differentiation are controlled in these contexts.
  • MicroRNA-29 Regulates T-Box Transcription Factors and Interferon-γ Production in Helper T Cells
    - Immunity 35(2):169-181 (2011)
    MicroRNA (miRNA)-deficient helper T cells exhibit abnormal IFN-γ production and decreased proliferation. However, the contributions of individual miRNAs to this phenotype remain poorly understood. We conducted a screen for miRNA function in primary T cells and identified individual miRNAs that rescue the defects associated with miRNA deficiency. Multiple members of the miR-17 and miR-92 families enhanced miRNA-deficient T cell proliferation whereas miR-29 largely corrected their aberrant interferon-γ (IFN-γ) expression. Repression of IFN-γ production by miR-29 involved direct targeting of both T-bet and Eomes, two transcription factors known to induce IFN-γ production. Although not usually expressed at functionally relevant amounts in helper T cells, Eomes was abundant in miRNA-deficient cells and was upregulated after miR-29 inhibition in wild-type cells. These results demonstrate that miR-29 regulates helper T cell differentiation by repressing multiple target g! enes, including at least two that are independently capable of inducing the T helper 1 (Th1) cell gene expression program.
  • Lysosomal Trafficking, Antigen Presentation, and Microbial Killing Are Controlled by the Arf-like GTPase Arl8b
    - Immunity 35(2):182-193 (2011)
    Antigen presentation and microbial killing are critical arms of host defense that depend upon cargo trafficking into lysosomes. Yet, the molecular regulators of traffic into lysosomes are only partly understood. Here, using a lysosome-dependent immunological screen of a trafficking shRNA library, we identified the Arf-like GTPase Arl8b as a critical regulator of cargo delivery to lysosomes. Homotypic fusion and vacuole protein sorting (HOPS) complex members were identified as effectors of Arl8b and were dependent on Arl8b for recruitment to lysosomes, suggesting that Arl8b-HOPS plays a general role in directing traffic to lysosomes. Moreover, the formation of CD1 antigen-presenting complexes in lysosomes, their delivery to the plasma membrane, and phagosome-lysosome fusion were all markedly impaired in Arl8b silenced cells resulting in corresponding defects in T cell activation and microbial killing. Together, these results define Arl8b as a key regulator of lysosomal ! cellular and immunological functions.
  • Innate Immune Recognition of an AT-Rich Stem-Loop DNA Motif in the Plasmodium falciparum Genome
    - Immunity 35(2):194-207 (2011)
    Although Toll-like receptor 9 (TLR9) has been implicated in cytokine and type I interferon (IFN) production during malaria in humans and mice, the high AT content of the Plasmodium falciparum genome prompted us to examine the possibility that malarial DNA triggered TLR9-independent pathways. Over 6000 ATTTTTAC ("AT-rich") motifs are present in the genome of P. falciparum, which we show here potently induce type I IFNs. Parasite DNA, parasitized erythrocytes and oligonucleotides containing the AT-rich motif induce type I IFNs via a pathway that did not involve the previously described sensors TLR9, DAI, RNA polymerase-III or IFI16/p204. Rather, AT-rich DNA sensing involved an unknown receptor that coupled to the STING, TBK1 and IRF3-IRF7 signaling pathway. Mice lacking IRF3, IRF7, the kinase TBK1 or the type I IFN receptor were resistant to otherwise lethal cerebral malaria. Collectively, these observations implicate AT-rich DNA sensing via STING, TBK1 and IRF3-IRF7! in P. falciparum malaria.
  • T Cell Receptor Internalization from the Immunological Synapse Is Mediated by TC21 and RhoG GTPase-Dependent Phagocytosis
    - Immunity 35(2):208-222 (2011)
    The immunological synapse (IS) serves a dual role for sustained T cell receptor (TCR) signaling and for TCR downregulation. TC21 (Rras2) is a RRas subfamily GTPase that constitutively associates with the TCR and is implicated in tonic TCR signaling by activating phosphatidylinositol 3-kinase. In this study, we demonstrate that TC21 both cotranslocates with the TCR to the IS and is necessary for TCR internalization from the IS through a mechanism dependent on RhoG, a small GTPase previously associated with phagocytosis. Indeed, we found that the TCR triggers T cells to phagocytose 1–6 μm beads through a TC21- and RhoG-dependent pathway. We further show that TC21 and RhoG are necessary for the TCR-promoted uptake of major histocompatibility complex (MHC) from antigen-presenting cells. Therefore, TC21 and RhoG dependence underlie the existence of a common phagocytic mechanism that drives TCR internalization from the IS together with its peptide-MHC ligand.
  • Thymic Stromal Lymphopoetin-Induced Expression of the Endogenous Inhibitory Enzyme SLPI Mediates Recovery from Colonic Inflammation
    - Immunity 35(2):223-235 (2011)
    Thymic stromal lymphopoetin (TSLP) influences numerous immune functions, including those in the colonic mucosa. Here we report that TSLP-deficient (Tslp−/−) mice did not exhibit increased inflammation during dextran sodium sulfate (DSS)-induced colitis but failed to recover from disease, resulting in death. Increased localized neutrophil elastase (NE) activity during overt inflammation was observed in Tslp−/− mice and was paralleled by reduced expression of an endogenous inhibitor, secretory leukocyte peptidase inhibitor (SLPI). Pharmacological inhibition of NE or treatment with rSLPI reduced DSS-induced mortality in Tslp−/− mice. Signaling through TSLPR on nonhematopoietic cells was sufficient for recovery from DSS-induced colitis. Expression of the receptor occurred on intestinal epithelial cells (IEC), with stimulation inducing SLPI expression. Therefore, TSLP is critical in mediating mucosal healing after insult and functions in a nonredundant capacity ! that is independent of restraining T helper 1 (Th1) and Th17 cell cytokine production.
  • CD8α+ Dendritic Cells Are an Obligate Cellular Entry Point for Productive Infection by Listeria monocytogenes
    - Immunity 35(2):236-248 (2011)
    CD8α+ dendritic cells (DCs) prime cytotoxic T lymphocytes during viral infections and produce interleukin-12 in response to pathogens. Although the loss of CD8α+ DCs in Batf3−/− mice increases their susceptibility to several pathogens, we observed that Batf3−/− mice exhibited enhanced resistance to the intracellular bacterium Listeria monocytogenes. In wild-type mice, Listeria organisms, initially located in the splenic marginal zone, migrated to the periarteriolar lymphoid sheath (PALS) where they grew exponentially and induced widespread lymphocyte apoptosis. In Batf3−/− mice, however, Listeria organisms remain trapped in the marginal zone, failed to traffic into the PALS, and were rapidly cleared by phagocytes. In addition, Batf3−/− mice, which lacked the normal population of hepatic CD103+ peripheral DCs, also showed protection from liver infection. These results suggest that Batf3-dependent CD8α+ and CD103+ DCs provide initial cellular entry poi! nts within the reticuloendothelial system by which Listeria establishes productive infection.
  • CD8α+ Dendritic Cells Are the Critical Source of Interleukin-12 that Controls Acute Infection by Toxoplasma gondii Tachyzoites
    - Immunity 35(2):249-259 (2011)
    CD8α+ dendritic cells (DCs) are important in vivo for cross-presentation of antigens derived from intracellular pathogens and tumors. Additionally, secretion of interleukin-12 (IL-12) by CD8α+ DCs suggests a role for these cells in response to Toxoplasma gondii antigens, although it remains unclear whether these cells are required for protection against T. gondii infection. Toward this goal, we examined T. gondii infection of Batf3−/− mice, which selectively lack only lymphoid-resident CD8α+ DCs and related peripheral CD103+ DCs. Batf3−/− mice were extremely susceptible to T. gondii infection, with decreased production of IL-12 and interferon-γ. IL-12 administration restored resistance in Batf3−/− mice, and mice in which IL-12 production was ablated only from CD8α+ DCs failed to control infection. These results reveal that the function of CD8α+ DCs extends beyond a role in cross-presentation and includes a critical role for activation of innate immuni! ty through IL-12 production during T. gondii infection.
  • Skin-Resident Murine Dendritic Cell Subsets Promote Distinct and Opposing Antigen-Specific T Helper Cell Responses
    - Immunity 35(2):260-272 (2011)
    Skin-resident dendritic cells (DCs) are well positioned to encounter cutaneous pathogens and are required for the initiation of adaptive immune responses. There are at least three subsets of skin DC— Langerhans cells (LC), Langerin+ dermal DCs (dDCs), and classic dDCs. Whether these subsets have distinct or redundant function in vivo is poorly understood. Using a Candida albicans skin infection model, we have shown that direct presentation of antigen by LC is necessary and sufficient for the generation of antigen-specific T helper-17 (Th17) cells but not for the generation of cytotoxic lymphocytes (CTLs). In contrast, Langerin+ dDCs are required for the generation of antigen specific CTL and Th1 cells. Langerin+ dDCs also inhibited the ability of LCs and classic DCs to promote Th17 cell responses. This work demonstrates that skin-resident DC subsets promote distinct and opposing antigen-specific responses.
  • Leukemia Inhibitory Factor Inhibits T Helper 17 Cell Differentiation and Confers Treatment Effects of Neural Progenitor Cell Therapy in Autoimmune Disease
    - Immunity 35(2):273-284 (2011)
    Neural progenitor cell (NPC) therapy is considered a promising treatment modality for multiple sclerosis (MS), potentially acting through neural repair. Here, we showed that intravenous administration of NPCs ameliorated experimental autoimmune encephalomyelitis (EAE) by selectively inhibiting pathogenic T helper 17 (Th17) cell differentiation. Leukemia inhibitory factor (LIF) produced by NPCs was responsible for the observed EAE suppression. Through the inducible LIF receptor expression, LIF inhibited the differentiation of Th17 cells in EAE mice and that from MS subjects. At the molecular level, LIF exerted an opposing effect on interleukin 6 (IL-6)-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation required for Th17 cell differentiation by triggering a signaling cascade that activated extracellular signal-regulated MAP kinase (ERK) and upregulated suppressor of cytokine signaling 3 (SOCS3) expression. This study reveals a critical rol! e for LIF in regulating Th17 cell differentiation and provides insights into the mechanisms of action of NPC therapy in MS.
  • Tight Regulation of Memory CD8+ T Cells Limits Their Effectiveness during Sustained High Viral Load
    - Immunity 35(2):285-298 (2011)
    To design successful vaccines for chronic diseases, an understanding of memory CD8+ T cell responses to persistent antigen restimulation is critical. However, most studies comparing memory and naive cell responses have been performed only in rapidly cleared acute infections. Herein, by comparing the responses of memory and naive CD8+ T cells to acute and chronic lymphocytic choriomeningitis virus infection, we show that memory cells dominated over naive cells and were protective when present in sufficient numbers to quickly reduce infection. In contrast, when infection was not rapidly reduced, because of high antigen load or persistence, memory cells were quickly lost, unlike naive cells. This loss of memory cells was due to a block in sustaining cell proliferation, selective regulation by the inhibitory receptor 2B4, and increased reliance on CD4+ T cell help. Thus, emphasizing the importance of designing vaccines that elicit effective CD4+ T cell help and rapidly con! trol infection.
  • Genome-wide Analyses of Transcription Factor GATA3-Mediated Gene Regulation in Distinct T Cell Types
    - Immunity 35(2):299-311 (2011)
    The transcription factor GATA3 plays an essential role during T cell development and T helper 2 (Th2) cell differentiation. To understand GATA3-mediated gene regulation, we identified genome-wide GATA3 binding sites in ten well-defined developmental and effector T lymphocyte lineages. In the thymus, GATA3 directly regulated many critical factors, including Th-POK, Notch1, and T cell receptor subunits. In the periphery, GATA3 induced a large number of Th2 cell-specific as well as Th2 cell-nonspecific genes, including several transcription factors. Our data also indicate that GATA3 regulates both active and repressive histone modifications of many target genes at their regulatory elements near GATA3 binding sites. Overall, although GATA3 binding exhibited both shared and cell-specific patterns among various T cell lineages, many genes were either positively or negatively regulated by GATA3 in a cell type-specific manner, suggesting that GATA3-mediated gene regulation dep! ends strongly on cofactors existing in different T cells.

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