Hot off the presses! Jun 19 Immunity

The Jun 19 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:

• cIAP Proteins: Keystones in NOD Receptor Signal Transduction
  - Immunity 30(6):755-756 (2009)
  NOD1 and 2 are intracellular sentinels critical to innate immunity. In this issue of Immunity, Bertrand et al. (2009) fill in a gap in the NOD signaling cascade by demonstrating that cIAP1 and 2 function as E3 ubiquitin ligases for the RIP2 signaling molecule.
• PLZF Outreach: A Finger in Interferon's Pie
  - Immunity 30(6):757-758 (2009)
  In this issue of Immunity, Xu et al. (2009) find that the transcription factor PLZF activates interferon-stimulated genes and facilitates natural killer cell functions. Interferon-induced PLZF phosphorylation and histone deacetylase 1 recruitment probably mediates the repressor-to-activator conversion.
• m(en)TOR(ing) Differentiating T Helper Cells
  - Immunity 30(6):759-761 (2009)
  The decision of naive Th cells to assume the fate of effector or regulator Th cells heavily influences the outcome of adaptive immune responses. In this issue of Immunity, Delgoffe et al. (2009) use genetic approaches and demonstrate that mTOR kinase plays a critical role in this decision-making process.
• Knocking In the NLRP3 Inflammasome
  - Immunity 30(6):761-763 (2009)
  Mutations in the human NLRP3 gene cause interleukin-1β-related autoinflammatory syndromes. In this issue of Immunity, Brydges et al. (2009) and Meng et al. (2009) report the characterization of Nlrp3 gene-targeted mice harboring mutations mimicking those causing disease in humans.
• The Fate of Human Treg Cells
  - Immunity 30(6):763-765 (2009)
  In this issue of Immunity, Miyara et al. (2009) demonstrate that FoxP3+ cells in human peripheral blood are heterogeneous in function, and CD45RA expression defines their different stages of differentiation.
• Approaching the Asymptote: 20 Years Later
  - Immunity 30(6):766-775 (2009)
  The pattern recognition theory proposed by the late Charles Janeway, Jr. 20 years ago provided a conceptual framework for our current understanding of the innate immune recognition and its role in the activation of adaptive immunity. Discovery of several families of pattern recognition receptors and their roles in mammalian immunity provided experimental support for the Janeway's theory. In addition to pattern recognition, there are other forms of innate immune sensing, which presumably work in specific combinations depending on the pathogen class and the type of the immune response they elicit. Here, the development of the Janeway's theory is discussed in the context of the advances made in field of innate immune recognition over the past two decades. "It is amateurs who have one big bright beautiful idea that they can never abandon. Professionals know that they have to produce theory after theory before they are likely to hit the jackpot." Francis Crick, What Mad Pursuit: A Personal View of Scientific Discovery (1988)
• Antigen Ligation Triggers a Conformational Change within the Constant Domain of the αβ T Cell Receptor
  - Immunity 30(6):777-788 (2009)
  Ligation of the αβ T cell receptor (TCR) by a specific peptide-loaded major histocompatibility complex (pMHC) molecule initiates T cell signaling via the CD3 complex. However, the initial events that link antigen recognition to T cell signal transduction remain unclear. Here we show, via fluorescence-based experiments and structural analyses, that MHC-restricted antigen recognition by the αβ TCR results in a specific conformational change confined to the A-B loop within the α chain of the constant domain (Cα). The apparent affinity constant of this A-B loop movement mirrored that of αβ TCR-pMHC ligation and was observed in two αβ TCRs with distinct pMHC specificities. The Ag-induced A-B loop conformational change could be inhibited by fixing the juxtapositioning of the constant domains and was shown to be reversible upon pMHC disassociation. Notably, the loop movement within the Cα domain, although specific for an agonist pMHC ligand, was not observed with a! pMHC antagonist. Moreover, mutagenesis of residues within the A-B loop impaired T cell signaling in an in vitro system of antigen-specific TCR stimulation. Collectively, our findings provide a basis for the earliest molecular events that underlie Ag-induced T cell triggering.
• Cellular Inhibitors of Apoptosis cIAP1 and cIAP2 Are Required for Innate Immunity Signaling by the Pattern Recognition Receptors NOD1 and NOD2
  - Immunity 30(6):789-801 (2009)
  Cellular inhibitor of apoptosis proteins (cIAPs) block apoptosis, but their physiological functions are still under investigation. Here, we report that cIAP1 and cIAP2 are E3 ubiquitin ligases that are required for receptor-interacting protein 2 (RIP2) ubiquitination and for nucleotide-binding and oligomerization (NOD) signaling. Macrophages derived from Birc2−/− or Birc3−/− mice, or colonocytes depleted of cIAP1 or cIAP2 by RNAi, were defective in NOD signaling and displayed sharp attenuation of cytokine and chemokine production. This blunted response was observed in vivo when Birc2−/− and Birc3−/− mice were challenged with NOD agonists. Defects in NOD2 signaling are associated with Crohn's disease, and muramyl dipeptide (MDP) activation of NOD2 signaling protects mice from experimental colitis. Here, we show that administration of MDP protected wild-type but not Ripk2−/− or Birc3−/− mice from colitis, confirming the role of the cIAPs in NOD2 s! ignaling in vivo. This discovery provides therapeutic opportunities in the treatment of NOD-dependent immunologic and inflammatory diseases.
• Promyelocytic Leukemia Zinc Finger Protein Regulates Interferon-Mediated Innate Immunity
  - Immunity 30(6):802-816 (2009)
  Interferons (IFNs) direct innate and acquired immune responses and, accordingly, are used therapeutically to treat a number of diseases, yet the diverse effects they elicit are not fully understood. Here, we identified the promyelocytic leukemia zinc finger (PLZF) protein as a previously unrecognized component of the IFN response. IFN stimulated an association of PLZF with promyelocytic leukemia protein (PML) and histone deacetylase 1 (HDAC1) to induce a decisive subset of IFN-stimulated genes (ISGs). Consequently, PLZF-deficient mice had a specific ISG expression defect and as a result were more susceptible to viral infection. This susceptibility correlated with a marked decrease in the expression of the key antiviral mediators and an impaired IFN-mediated induction of natural killer cell function. These results provide new insights into the regulatory mechanisms of IFN signaling and the induction of innate antiviral immunity.
• A Central Nervous System-Restricted Isoform of the Interleukin-1 Receptor Accessory Protein Modulates Neuronal Responses to Interleukin-1
  - Immunity 30(6):817-831 (2009)
  Interleukin-1 (IL-1) has multiple functions in both the periphery and the central nervous system (CNS) and is regulated at many levels. We identified an isoform of the IL-1 receptor (IL-1R) accessory protein (termed AcPb) that is expressed exclusively in the CNS. AcPb interacted with IL-1 and the IL-1R but was unable to mediate canonical IL-1 responses. AcPb expression, however, modulated neuronal gene expression in response to IL-1 treatment in vitro. Animals lacking AcPb demonstrated an intact peripheral IL-1 response and developed experimental autoimmune encephalomyelitis (EAE) similarly to wild-type mice. AcPb-deficient mice were instead more vulnerable to local inflammatory challenge in the CNS and suffered enhanced neuronal degeneration as compared to AcP-deficient or wild-type mice. These findings implicate AcPb as an additional component of the highly regulated IL-1 system and suggest that it may play a role in modulating CNS responses to IL-1 and the interplay! between inflammation and neuronal survival.
• The mTOR Kinase Differentially Regulates Effector and Regulatory T Cell Lineage Commitment
  - Immunity 30(6):832-844 (2009)
  Effector T cell differentiation requires the simultaneous integration of multiple, and sometimes opposing, cytokine signals. We demonstrated mTOR's role in dictating the outcome of T cell fate. mTOR-deficient T cells displayed normal activation and IL-2 production upon initial stimulation. However, such cells failed to differentiate into T helper 1 (Th1), Th2, or Th17 effector cells. The inability to differentiate was associated with decreased STAT transcription factor activation and failure to upregulate lineage-specific transcription factors. Under normally activating conditions, T cells lacking mTOR differentiated into Foxp3+ regulatory T cells. This was associated with hyperactive Smad3 activation in the absence of exogenous TGF-β. Surprisingly, T cells selectively deficient in TORC1 do not divert to a regulatory T cell pathway, implicating both TORC1 and TORC2 in preventing the generation of regulatory T cells. Overall, our studies suggest that mTOR kinase signal! ing regulates decisions between effector and regulatory T cell lineage commitment.
• Notch and Wingless Signaling Cooperate in Regulation of Dendritic Cell Differentiation
  - Immunity 30(6):845-859 (2009)
  Dendritic cell (DC) differentiation is regulated by stroma via a network of soluble and cell-bound factors. Notch is one of the major elements of this network. Its role in DC differentiation, however, is controversial. Here, we demonstrate that activation of Notch signaling in hematopoietic progenitor cells (HPCs) promoted differentiation of conventional DCs via activation of the canonical Wingless (Wnt) pathway. Inhibition of the Wnt pathway abrogated the effect of Notch on DC differentiation. The fact that activation of the Wnt pathway in Notch-1-deficient embryonic stem cells restored DC differentiation indicates that Wnt signaling is downstream of the Notch pathway in regulating DC differentiation. Notch signaling activated the Wnt pathway in HPCs via expression of multiple members of the Frizzled family of Wnt receptors, which was directly regulated by the CSL (RPB-Jκ) transcription factor. Thus, these data suggest a model of DC differentiation via cooperation be! tween Wnt and Notch pathways.
• A Mutation in the Nlrp3 Gene Causing Inflammasome Hyperactivation Potentiates Th17 Cell-Dominant Immune Responses
  - Immunity 30(6):860-874 (2009)
  Missense mutations of the gene encoding NLRP3 are associated with autoinflammatory disorders characterized with excessive production of interleukin-1β (IL-1β). Here we analyzed the immune responses of gene-targeted mice carrying a mutation in the Nlrp3 gene equivalent to the human mutation associated with Muckle-Wells Syndrome. We found that antigen-presenting cells (APCs) from such mice produced massive amounts of IL-1β upon stimulation with microbial stimuli in the absence of ATP. This was likely due to a diminished inflammasome activation threshold that allowed a response to the small amount of agonist. Moreover, the Nlrp3 gene-targeted mice exhibited skin inflammation characterized by neutrophil infiltration and a Th17 cytokine-dominant response, which originated from hematopoietic cells. The inflammation of Nlrp3 gene-targeted mice resulted from excess IL-1β production from APCs, which augmented Th17 cell differentitation. These results demonstrate that the NL! RP3 mutation leads to inflammasome hyperactivation and consequently Th17 cell-dominant immunopathology in autoinflammation.
• Inflammasome-Mediated Disease Animal Models Reveal Roles for Innate but Not Adaptive Immunity
  - Immunity 30(6):875-887 (2009)
  NLRP3 nucleates the inflammasome, a protein complex responsible for cleavage of prointerleukin-1β (IL-1β) to its active form. Mutations in the NLRP3 gene cause the autoinflammatory disease spectrum cryopyrin-associated periodic syndromes (CAPS). The central role of IL-1β in CAPS is supported by the response to IL-1-targeted therapy. We developed two Nlrp3 mutant knockin mouse strains to model CAPS to examine the role of other inflammatory mediators and adaptive immune responses in an innate immune-driven disease. These mice had systemic inflammation and poor growth, similar to some human CAPS patients, and demonstrated early mortality, primarily mediated by myeloid cells. Mating these mutant mice to various gene mutant backgrounds showed that the mouse disease phenotype required an intact inflammasome, was only partially dependent on IL-1β, and was independent of T cells. These data suggest that CAPS are true inflammasome-mediated diseases and provide insight for m! ore common inflammatory disorders.
• Kinetics and Cellular Site of Glycolipid Loading Control the Outcome of Natural Killer T Cell Activation
  - Immunity 30(6):888-898 (2009)
  CD1d-restricted natural killer T cells (NKT cells) possess a wide range of effector and regulatory activities that are related to their ability to secrete both T helper 1 (Th1) cell- and Th2 cell-type cytokines. We analyzed presentation of NKT cell activating α galactosylceramide (αGalCer) analogs that give predominantly Th2 cell-type cytokine responses to determine how ligand structure controls the outcome of NKT cell activation. Using a monoclonal antibody specific for αGalCer-CD1d complexes to visualize and quantitate glycolipid presentation, we found that Th2 cell-type cytokine-biasing ligands were characterized by rapid and direct loading of cell-surface CD1d proteins. Complexes formed by association of these Th2 cell-type cytokine-biasing αGalCer analogs with CD1d showed a distinctive exclusion from ganglioside-enriched, detergent-resistant plasma membrane microdomains of antigen-presenting cells. These findings help to explain how subtle alterations in glyco! lipid ligand structure can control the balance of proinflammatory and anti-inflammatory activities of NKT cells.
• Functional Delineation and Differentiation Dynamics of Human CD4+ T Cells Expressing the FoxP3 Transcription Factor
  - Immunity 30(6):899-911 (2009)
  FoxP3 is a key transcription factor for the development and function of natural CD4+ regulatory T cells (Treg cells). Here we show that human FoxP3+CD4+ T cells were composed of three phenotypically and functionally distinct subpopulations: CD45RA+FoxP3lo resting Treg cells (rTreg cells) and CD45RA−FoxP3hi activated Treg cells (aTreg cells), both of which were suppressive in vitro, and cytokine-secreting CD45RA−FoxP3lo nonsuppressive T cells. The proportion of the three subpopulations differed between cord blood, aged individuals, and patients with immunological diseases. Terminally differentiated aTreg cells rapidly died whereas rTreg cells proliferated and converted into aTreg cells in vitro and in vivo. This was shown by the transfer of rTreg cells into NOD-scid-common γ-chain-deficient mice and by TCR sequence-based T cell clonotype tracing in peripheral blood in a normal individual. Taken together, the dissection of FoxP3+ cells into subsets enables one to an! alyze Treg cell differentiation dynamics and interactions in normal and disease states, and to control immune responses through manipulating particular FoxP3+ subpopulations.
• Genome-wide Analysis of Histone Methylation Reveals Chromatin State-Based Regulation of Gene Transcription and Function of Memory CD8+ T Cells
  - Immunity 30(6):912-925 (2009)
  Memory lymphocytes are characterized by their ability to exhibit a rapid response to the recall antigen, in which differential transcription is important, yet the underlying mechanism is not understood. We report here a genome-wide analysis of histone methylation on two histone H3 lysine residues (H3K4me3 and H3K27me3) and gene expression profiles in naive and memory CD8+ T cells. We found that specific correlation exists between gene expression and the amounts of H3K4me3 (positive correlation) and H3K27me3 (negative correlation) across the gene body. These correlations displayed four distinct modes (repressive, active, poised, and bivalent), reflecting different functions of these genes in CD8+ T cells. Furthermore, a permissive chromatin state of each gene was established by a combination of different histone modifications. Our findings reveal a complex regulation by histone methylation in differential gene expression and suggest that histone methylation may be respo! nsible for memory CD8+ T cell function.