Journal of Experimental Medicine recent issues

Cholesterol Promotes Hemifusion and Pore Widening in Membrane Fusion Induced by Influenza Hemagglutinin

Biswas, S., Yin, S.-R., Blank, P. S., Zimmerberg, J. — 2008-05-12

Prion protein attenuates excitotoxicity by inhibiting NMDA receptors

2008-05-12

All quiet on the neuronal front: NMDA receptor inhibition by prion protein

Steele, A. D. — 2008-05-12

You wrote it; you own it!

Hill, E., Rossner, M. — 2008-05-12

Authors of papers published in Rockefeller University Press journals (The Journal of Cell Biology, The Journal of Experimental Medicine, or The Journal of General Physiology) now retain copyright to their published work. This permits authors to reuse their own work in any way, as long as they attribute it to the original publication. Third parties may use our published materials under a Creative Commons license, six months after publication.

New targets for aspirin

Bashyam, H. — 2008-05-12

Spreading instead of growing

Bashyam, H. — 2008-05-12

Weakening HIV

Bashyam, H. — 2008-05-12

A trick presentation

Bashyam, H. — 2008-05-12

Dangers of restocking T cells

Bashyam, H. — 2008-05-12

Susan Allen: Confronting HIV in Africa

Bashyam, H. — 2008-05-12

Crippling HIV one mutation at a time

Allen, T. M., Altfeld, M. — 2008-05-12

Accumulating data suggest that not all human immunodeficiency virus (HIV)-1–specific immune responses are equally effective at controlling HIV-1 replication. A new study now demonstrates that multiple immune-driven sequence polymorphisms in the highly conserved HIV-1 Gag region of transmitted viruses are associated with reduced viral replication in newly infected humans. These data suggest that targeting these and other conserved viral regions may be the key to developing an effective HIV-1 vaccine.

Transmission of HIV-1 Gag immune escape mutations is associated with reduced viral load in linked recipients

2008-05-12

In a study of 114 epidemiologically linked Zambian transmission pairs, we evaluated the impact of human leukocyte antigen class I (HLA-I)–associated amino acid polymorphisms, presumed to reflect cytotoxic T lymphocyte (CTL) escape in Gag and Nef of the virus transmitted from the chronically infected donor, on the plasma viral load (VL) in matched recipients 6 mo after infection. CTL escape mutations in Gag and Nef were seen in the donors, which were subsequently transmitted to recipients, largely unchanged soon after infection. We observed a significant correlation between the number of Gag escape mutations targeted by specific HLA-B allele–restricted CTLs and reduced VLs in the recipients. This negative correlation was most evident in newly infected individuals, whose HLA alleles were unable to effectively target Gag and select for CTL escape mutations in this gene. Nef mutations in the donor had no impact on VL in the recipient. Thus, broad Gag-specific CTL responses capable of driving virus escape in the donor may be of clinical benefit to both the donor and recipient. In addition to their direct implications for HIV-1 vaccine design, these data suggest that CTL-induced viral polymorphisms and their associated in vivo viral fitness costs could have a significant impact on HIV-1 pathogenesis.

IL-6-dependent spontaneous proliferation is required for the induction of colitogenic IL-17-producing CD8+ T cells

2008-05-12

We propose a novel role for interleukin (IL) 6 in inducing rapid spontaneous proliferation (SP) of naive CD8⁺ T cells, which is a crucial step in the differentiation of colitogenic CD8⁺ T cells. Homeostasis of T cells is regulated by two distinct modes of cell proliferation: major histocompatibility complex/antigen–driven rapid SP and IL-7/IL-15–dependent slow homeostatic proliferation. Using our novel model of CD8⁺ T cell–dependent colitis, we found that SP of naive CD8⁺ T cells is essential for inducing pathogenic cytokine-producing effector T cells. The rapid SP was predominantly induced in mesenteric lymph nodes (LNs) but not in peripheral LNs under the influence of intestinal flora and IL-6. Indeed, this SP was markedly inhibited by treatment with anti–IL-6 receptor monoclonal antibody (IL-6R mAb) or antibiotic-induced flora depletion, but not by anti–IL-7R mAb and/or in IL-15–deficient conditions. Concomitantly with the inhibition of SP, anti–IL-6R mAb significantly inhibited the induction of CD8⁺ T cell–dependent autoimmune colitis. Notably, the transfer of naive CD8⁺ T cells derived from IL-17^–/– mice did not induce autoimmune colitis. Thus, we conclude that IL-6 signaling is crucial for SP under lymphopenic conditions, which subsequently caused severe IL-17–producing CD8⁺ T cell–mediated autoimmune colitis. We suggest that anti–IL-6R mAb may become a promising strategy for the therapy of colitis.

During negative selection, Nur77 family proteins translocate to mitochondria where they associate with Bcl-2 and expose its proapoptotic BH3 domain

Thompson, J., Winoto, A. — 2008-05-12

Apoptosis accompanying negative selection is a central but poorly understood event in T cell development. The Nur77 nuclear steroid receptor and Bim, a proapoptotic BH3-only member of the Bcl-2 family, are two molecules implicated in this process. However, how they relate to each other and how Nur77 induces apoptosis remain unclear. In thymocytes, Nur77 has been shown to induce cell death through a transcriptional-dependent pathway, but in cancer cell lines, Nur77 was reported to induce apoptosis through conversion of Bcl-2 into a killer protein at the mitochondria. Whether this Nur77 transcriptional-independent pathway actually occurs in vivo remains controversial. Using an optimized fractionation protocol for thymocytes, here we report that stimulation of CD4⁺CD8⁺ thymocytes results in translocation of Nur77 and its family member Nor-1 to the mitochondria, leading to their association with Bcl-2 and exposure of the Bcl-2 proapoptotic BH3 domain. In two T cell receptor transgenic models of negative selection, F5 and HY, a conformational change of the Bcl-2 molecule in the negatively selected T cell population was similarly observed. Thus, the Nur77 family and Bim pathways converge at mitochondria to mediate negative selection.

Essential role of TNF receptor superfamily 25 (TNFRSF25) in the development of allergic lung inflammation

Fang, L., Adkins, B., Deyev, V., Podack, E. R. — 2008-05-12

We identify the tumor necrosis factor receptor superfamily 25 (TNFRSF25)/TNFSF15 pair as critical trigger for allergic lung inflammation, which is a cardinal feature of asthma. TNFRSF25 (TNFR25) signals are required to exert T helper cell 2 (Th2) effector function in Th2-polarized CD4 cells and co-stimulate interleukin (IL)-13 production by glycosphingolipid-activated NKT cells. In vivo, antibody blockade of TNFSF15 (TL1A), which is the ligand for TNFR25, inhibits lung inflammation and production of Th2 cytokines such as IL-13, even when administered days after airway antigen exposure. Similarly, blockade of TNFR25 by a dominant-negative (DN) transgene, DN TNFR25, confers resistance to lung inflammation in mice. Allergic lung inflammation–resistant, NKT-deficient mice become susceptible upon adoptive transfer of wild-type NKT cells, but not after transfer of DN TNFR25 transgenic NKT cells. The TNFR25/TL1A pair appears to provide an early signal for Th2 cytokine production in the lung, and therefore may be a drug target in attempts to attenuate lung inflammation in asthmatics.

TL1A-DR3 interaction regulates Th17 cell function and Th17-mediated autoimmune disease

2008-05-12

T helper type 17 (Th17) cells play an important pathogenic function in autoimmune diseases; their regulation, however, is not well understood. We show that the expression of a tumor necrosis factor receptor family member, death receptor 3 (DR3; also known as TNFRSF25), is selectively elevated in Th17 cells, and that TL1A, its cognate ligand, can promote the proliferation of effector Th17 cells. To further investigate the role of the TL1A–DR3 pathway in Th17 regulation, we generated a TL1A-deficient mouse and found that TL1A^–/– dendritic cells exhibited a reduced capacity in supporting Th17 differentiation and proliferation. Consistent with these data, TL1A^–/– animals displayed decreased clinical severity in experimental autoimmune encephalomyelitis (EAE). Finally, we demonstrated that during EAE disease progression, TL1A was required for the optimal differentiation as well as effector function of Th17 cells. These observations thus establish an important role of the TL1A–DR3 pathway in promoting Th17 cell function and Th17-mediated autoimmune disease.

Regulation of inflammatory responses by IL-17F

2008-05-12

Although interleukin (IL) 17 has been extensively characterized, the function of IL-17F, which has an expression pattern regulated similarly to IL-17, is poorly understood. We show that like IL-17, IL-17F regulates proinflammatory gene expression in vitro, and this requires IL-17 receptor A, tumor necrosis factor receptor–associated factor 6, and Act1. In vivo, overexpression of IL-17F in lung epithelium led to infiltration of lymphocytes and macrophages and mucus hyperplasia, similar to observations made in IL-17 transgenic mice. To further understand the function of IL-17F, we generated and analyzed mice deficient in IL-17F or IL-17. IL-17, but not IL-17F, was required for the initiation of experimental autoimmune encephalomyelitis. Mice deficient in IL-17F, but not IL-17, had defective airway neutrophilia in response to allergen challenge. Moreover, in an asthma model, although IL-17 deficiency reduced T helper type 2 responses, IL-17F–deficient mice displayed enhanced type 2 cytokine production and eosinophil function. In addition, IL-17F deficiency resulted in reduced colitis caused by dextran sulfate sodium, whereas IL-17 knockout mice developed more severe disease. Our results thus demonstrate that IL-17F is an important regulator of inflammatory responses that seems to function differently than IL-17 in immune responses and diseases.

Native and aspirin-triggered lipoxins control innate immunity by inducing proteasomal degradation of TRAF6

2008-05-12

Innate immune signaling is critical for the development of protective immunity. Such signaling is, perforce, tightly controlled. Lipoxins (LXs) are eicosanoid mediators that play key counterregulatory roles during infection. The molecular mechanisms underlying LX-mediated control of innate immune signaling are of interest. In this study, we show that LX and aspirin (ASA)-triggered LX (ATL) inhibit innate immune signaling by inducing suppressor of cytokine signaling (SOCS) 2–dependent ubiquitinylation and proteasome-mediated degradation of TNF receptor–associated factor (TRAF) 2 and TRAF6, which are adaptor molecules that couple TNF and interleukin-1 receptor/Toll-like receptor family members to intracellular signaling events. LX-mediated degradation of TRAF6 inhibits proinflammatory cytokine production by dendritic cells. This restraint of innate immune signaling can be ablated by inhibition of proteasome function. In vivo, this leads to dysregulated immune responses, accompanied by increased mortality during infection. Proteasomal degradation of TRAF6 is a central mechanism underlying LX-driven immune counterregulation, and a hitherto unappreciated mechanism of action of ASA. These findings suggest a new molecular target for drug development for diseases marked by dysregulated inflammatory responses.

Essential role of Notch signaling in effector memory CD8+ T cell-mediated airway hyperresponsiveness and inflammation

2008-05-12

Adoptive transfer of in vivo–primed CD8⁺ T cells or in vitro–generated effector memory CD8⁺ T (T_EFF) cells restores airway hyperresponsiveness (AHR) and airway inflammation in CD8-deficient (CD8^–/–) mice. Examining transcription levels, there was a strong induction of Notch1 in T_EFF cells compared with central memory CD8⁺ T cells. Treatment of T_EFF cells with a -secretase inhibitor (GSI) strongly inhibited Notch signaling in these cells, and after adoptive transfer, GSI-treated T_EFF cells failed to restore AHR and airway inflammation in sensitized and challenged recipient CD8^–/– mice, or to enhance these responses in recipient wild-type (WT) mice. These effects of GSI were also associated with increased expression of the Notch ligand Delta1 in T_EFF cells. Treatment of sensitized and challenged WT mice with Delta1-Fc resulted in decreased AHR and airway inflammation accompanied by higher levels of interferon in bronchoalveolar lavage fluid. These results demonstrate a role for Notch in skewing the T cell response from a T helper (Th)2 to a Th1 phenotype as a consequence of the inhibition of Notch receptor activation and the up-regulation of the Notch ligand Delta1. These data are the first to show a functional role for Notch in the challenge phase of CD8⁺ T cell–mediated development of AHR and airway inflammation, and identify Delta1 as an important regulator of allergic airway inflammation.

A role for sex chromosome complement in the female bias in autoimmune disease

2008-05-12

Most autoimmune diseases are more common in women than in men. This may be caused by differences in sex hormones, sex chromosomes, or both. In this study, we determined if there was a contribution of sex chromosomes to sex differences in susceptibility to two immunologically distinct disease models, experimental autoimmune encephalomyelitis (EAE) and pristane-induced lupus. Transgenic SJL mice were created to permit a comparison between XX and XY within a common gonadal type. Mice of the XX sex chromosome complement, as compared with XY, demonstrated greater susceptibility to both EAE and lupus. This is the first evidence that the XX sex chromosome complement, as compared with XY, confers greater susceptibility to autoimmune disease.

Bmi1 regulates memory CD4 T cell survival via repression of the Noxa gene

2008-05-12

The maintenance of memory T cells is central to the establishment of immunological memory, although molecular details of the process are poorly understood. In the absence of the polycomb group (PcG) gene Bmi1, the number of memory CD4⁺ T helper (Th)1/Th2 cells was reduced significantly. Enhanced cell death of Bmi1^–/– memory Th2 cells was observed both in vivo and in vitro. Among various proapoptotic genes that are regulated by Bmi1, the expression of proapoptotic BH3-only protein Noxa was increased in Bmi1^–/– effector Th1/Th2 cells. The generation of memory Th2 cells was restored by the deletion of Noxa, but not by Ink4a and Arf. Direct binding of Bmi1 to the Noxa gene locus was accompanied by histone H3-K27 methylation. The recruitment of other PcG gene products and Dnmt1 to the Noxa gene was highly dependent on the expression of Bmi1. In addition, Bmi1 was required for DNA CpG methylation of the Noxa gene. Moreover, memory Th2-dependent airway inflammation was attenuated substantially in the absence of Bmi1. Thus, Bmi1 controls memory CD4⁺ Th1/Th2 cell survival and function through the direct repression of the Noxa gene.

Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression

2008-05-12

Antimicrobial factors are efficient defense components of the innate immunity, playing a crucial role in the intestinal homeostasis and protection against pathogens. In this study, we report that upon infection of polarized human intestinal cells in vitro, virulent Shigella flexneri suppress transcription of several genes encoding antimicrobial cationic peptides, particularly the human β-defensin hBD-3, which we show to be especially active against S. flexneri. This is an example of targeted survival strategy. We also identify the MxiE bacterial regulator, which controls a regulon encompassing a set of virulence plasmid-encoded effectors injected into host cells and regulating innate signaling, as being responsible for this dedicated regulatory process. In vivo, in a model of human intestinal xenotransplant, we confirm at the transcriptional and translational level, the presence of a dedicated MxiE-dependent system allowing S. flexneri to suppress expression of antimicrobial cationic peptides and promoting its deeper progression toward intestinal crypts. We demonstrate that this system is also able to down-regulate additional innate immunity genes, such as the chemokine CCL20 gene, leading to compromised recruitment of dendritic cells to the lamina propria of infected tissues. Thus, S. flexneri has developed a dedicated strategy to weaken the innate immunity to manage its survival and colonization ability in the intestine.

C5 deficiency and C5a or C5aR blockade protects against cerebral malaria

2008-05-12

Experimental infection of mice with Plasmodium berghei ANKA (PbA) provides a powerful model to define genetic determinants that regulate the development of cerebral malaria (CM). Based on the hypothesis that excessive activation of the complement system may confer susceptibility to CM, we investigated the role of C5/C5a in the development of CM. We show a spectrum of susceptibility to PbA in a panel of inbred mice; all CM-susceptible mice examined were found to be C5 sufficient, whereas all C5-deficient strains were resistant to CM. Transfer of the C5-defective allele from an A/J (CM resistant) onto a C57BL/6 (CM-susceptible) genetic background in a congenic strain conferred increased resistance to CM; conversely, transfer of the C5-sufficient allele from the C57BL/6 onto the A/J background recapitulated the CM-susceptible phenotype. The role of C5 was further explored in B10.D2 mice, which are identical for all loci other than C5. C5-deficient B10.D2 mice were protected from CM, whereas C5-sufficient B10.D2 mice were susceptible. Antibody blockade of C5a or C5a receptor (C5aR) rescued susceptible mice from CM. In vitro studies showed that C5a-potentiated cytokine secretion induced by the malaria product P. falciparum glycosylphosphatidylinositol and C5aR blockade abrogated these amplified responses. These data provide evidence implicating C5/C5a in the pathogenesis of CM.

Bone sialoprotein plays a functional role in bone formation and osteoclastogenesis

2008-05-12

Bone sialoprotein (BSP) and osteopontin (OPN) are both highly expressed in bone, but their functional specificities are unknown. OPN knockout (^–/–) mice do not lose bone in a model of hindlimb disuse (tail suspension), showing the importance of OPN in bone remodeling. We report that BSP^–/– mice are viable and breed normally, but their weight and size are lower than wild-type (WT) mice. Bone is undermineralized in fetuses and young adults, but not in older (≥12 mo) BSP^–/– mice. At 4 mo, BSP^–/– mice display thinner cortical bones than WT, but greater trabecular bone volume with very low bone formation rate, which indicates reduced resorption, as confirmed by lower osteoclast surfaces. Although the frequency of total colonies and committed osteoblast colonies is the same, fewer mineralized colonies expressing decreased levels of osteoblast markers form in BSP^–/– versus WT bone marrow stromal cultures. BSP^–/– hematopoietic progenitors form fewer osteoclasts, but their resorptive activity on dentin is normal. Tail-suspended BSP^–/– mice lose bone in hindlimbs, as expected. In conclusion, BSP deficiency impairs bone growth and mineralization, concomitant with dramatically reduced bone formation. It does not, however, prevent the bone loss resulting from loss of mechanical stimulation, a phenotype that is clearly different from OPN^–/– mice.

The tumor suppressor semaphorin 3B triggers a prometastatic program mediated by interleukin 8 and the tumor microenvironment

2008-05-12

Semaphorins are a large family of evolutionarily conserved morphogenetic molecules originally identified for their repelling role in axonal guidance. Intriguingly, semaphorins have recently been implicated in cancer progression (Neufeld, G., T. Lange, A. Varshavsky, and O. Kessler. 2007. Adv. Exp. Med. Biol. 600:118–131). In particular, semaphorin 3B (SEMA3B) is considered a putative tumor suppressor, and yet we found that it is expressed at high levels in many invasive and metastatic human cancers. By investigating experimental tumor models, we confirmed that SEMA3B expression inhibited tumor growth, whereas metastatic dissemination was surprisingly increased. We found that SEMA3B induced the production of interleukin (IL) 8 by tumor cells by activating the p38–mitogen-activated protein kinase pathway in a neuropilin 1–dependent manner. Silencing the expression of endogenous SEMA3B in tumor cells impaired IL-8 transcription. The release of IL-8, in turn, induced the recruitment of tumor-associated macrophages and metastatic dissemination to the lung, which could be rescued by blocking IL-8 with neutralizing antibodies. In conclusion, we report that SEMA3B exerts unexpected functions in cancer progression by fostering a prometastatic environment through elevated IL-8 secretion and recruitment of macrophages coupled to the suppression of tumor growth.

T cell receptor-instructed {alpha}{beta} versus {gamma}{delta} lineage commitment revealed by single-cell analysis

Kreslavsky, T., Garbe, A. I., Krueger, A., von Boehmer, H. — 2008-05-12

β and T cell lineages develop in the thymus from a common precursor. It is unclear at which stage of development commitment to these lineages takes place and in which way T cell receptor signaling contributes to the process. Recently, it was demonstrated that strong TCR signals favor lineage development, whereas weaker TCR signals promote β lineage fate. Two models have been proposed to explain these results. The first model suggests that commitment occurs after TCR expression and TCR signaling directly instructs lymphocytes to adopt one or the other lineage fate. The second model suggests that commitment occurs before TCR expression and that TCR signaling merely confirms the lineage choice. By tracing the fate of single T cell precursors, this study shows that there is no commitment to either the β or lineage before TCR expression and that modulation of TCR signaling in progeny of a single TCR-expressing cell changes lineage commitment.

The stream of precursors that colonizes the thymus proceeds selectively through the early T lineage precursor stage of T cell development

Benz, C., Martins, V. C., Radtke, F., Bleul, C. C. — 2008-05-12

T cell development in the thymus depends on continuous colonization by hematopoietic precursors. Several distinct T cell precursors have been identified, but whether one or several independent precursor cell types maintain thymopoiesis is unclear. We have used thymus transplantation and an inducible lineage-tracing system to identify the intrathymic precursor cells among previously described thymus-homing progenitors that give rise to the T cell lineage in the thymus. Extrathymic precursors were not investigated in these studies. Both approaches show that the stream of T cell lineage precursor cells, when entering the thymus, selectively passes through the early T lineage precursor (ETP) stage. Immigrating precursor cells do not exhibit characteristics of double-negative (DN) 1c, DN1d, or DN1e stages, or of populations containing the common lymphoid precursor 2 (CLP-2) or the thymic equivalent of circulating T cell progenitors (CTPs). It remains possible that an unknown hematopoietic precursor cell or previously described extrathymic precursors with a CLP, CLP-2, or CTP phenotype feed into T cell development by circumventing known intrathymic T cell lineage progenitor cells. However, it is clear that of the known intrathymic precursors, only the ETP population contributes significant numbers of T lineage precursors to T cell development.

MR1 uses an endocytic pathway to activate mucosal-associated invariant T cells

2008-05-12

Like CD1d-restricted iNKT cells, mucosal-associated invariant T cells (MAITs) are "innate" T cells that express a canonical TCR chain, have a memory phenotype, and rapidly secrete cytokines upon TCR ligation. Unlike iNKT cells, MAIT cells require the class Ib molecule MHC-related protein I (MR1), B cells, and gut flora for development and/or expansion, and they preferentially reside in the gut lamina propria. Evidence strongly suggests that MAIT cell activation is ligand-dependent, but the nature of MR1 ligand is unknown. In this study, we define a mechanism of endogenous antigen presentation by MR1 to MAIT cells. MAIT cell activation was dependent neither on a proteasome-processed ligand nor on the chaperoning by the MHC class I peptide loading complex. However, MAIT cell activation was enhanced by overexpression of MHC class II chaperones Ii and DM and was strikingly diminished by silencing endogenous Ii. Furthermore, inhibiting the acidification of the endocytic compartments reduced MR1 surface expression and ablated MAIT cell activation. The importance of the late endosome for MR1 antigen presentation was further corroborated by the localization of MR1 molecules in the multivesicular endosomes. These findings demonstrate that MR1 traffics through endocytic compartments, thereby allowing MAIT cells to sample both endocytosed and endogenous antigens.

IL-15R{alpha} chaperones IL-15 to stable dendritic cell membrane complexes that activate NK cells via trans presentation

Mortier, E., Woo, T., Advincula, R., Gozalo, S., Ma, A. — 2008-05-12

Natural killer (NK) cells are innate immune effectors that mediate rapid responses to viral antigens. Interleukin (IL)-15 and its high affinity IL-15 receptor, IL-15R, support NK cell homeostasis in resting animals via a novel trans presentation mechanism. To better understand how IL-15 and IL-15R support NK cell activation during immune responses, we have used sensitive assays for detecting native IL-15 and IL-15R proteins and developed an assay for detecting complexes of these proteins. We find that IL-15 and IL-15R are preassembled in complexes within the endoplasmic reticulum/Golgi of stimulated dendritic cells (DCs) before being released from cells. IL-15R is required for IL-15 production by DCs, and IL-15 that emerges onto the cell surface of matured DCs does not bind to neighboring cells expressing IL-15R. We also find that soluble IL-15–IL-15R complexes are induced during inflammation, but membrane-bound IL-15–IL-15R complexes, rather than soluble complexes, support NK cell activation in vitro and in vivo. Finally, we provide in vivo evidence that expression of IL-15R specifically on DCs is critical for trans presenting IL-15 and activating NK cells. These studies define an unprecedented cytokine–receptor biosynthetic pathway in which IL-15R serves as a chaperone for IL-15, after which membrane-bound IL-15R–IL-15 complexes activate NK cells via direct cell–cell contact.

ATF4 is an oxidative stress-inducible, prodeath transcription factor in neurons in vitro and in vivo

2008-05-12

Oxidative stress is pathogenic in neurological diseases, including stroke. The identity of oxidative stress–inducible transcription factors and their role in propagating the death cascade are not well known. In an in vitro model of oxidative stress, the expression of the bZip transcription factor activating transcription factor 4 (ATF4) was induced by glutathione depletion and localized to the promoter of a putative death gene in neurons. Germline deletion of ATF4 resulted in a profound reduction in oxidative stress–induced gene expression and resistance to oxidative death. In neurons, ATF4 modulates an early, upstream event in the death pathway, as resistance to oxidative death by ATF4 deletion was associated with decreased consumption of the antioxidant glutathione. Forced expression of ATF4 was sufficient to promote cell death and loss of glutathione. In ATF4^–/– neurons, restoration of ATF4 protein expression reinstated sensitivity to oxidative death. In addition, ATF4^–/– mice experienced significantly smaller infarcts and improved behavioral recovery as compared with wild-type mice subjected to the same reductions in blood flow in a rodent model of ischemic stroke. Collectively, these findings establish ATF4 as a redox-regulated, prodeath transcriptional activator in the nervous system that propagates death responses to oxidative stress in vitro and to stroke in vivo.

Phospholipase C-{gamma}2 and Vav cooperate within signaling microclusters to propagate B cell spreading in response to membrane-bound antigen

2008-05-12

Impaired ubiquitin-proteasome system activity in the synapses of Huntington's disease mice

Wang, J., Wang, C.-E., Orr, A., Tydlacka, S., Li, S.-H., Li, X.-J. — 2008-04-14

Nuclear envelope defects cause stem cell dysfunction in premature-aging mice

2008-04-14

Gone with the Wnt/Notch: stem cells in laminopathies, progeria, and aging

Meshorer, E., Gruenbaum, Y. — 2008-04-14

How alum works

Bashyam, H. — 2008-04-14

OX40: a win-win path to tumor immunity

Sedwick, C. — 2008-04-14

A safer poxvirus vaccine

Bashyam, H. — 2008-04-14

Flushing out neutrophils

Bashyam, H. — 2008-04-14

A matter of (V segment) choice

Sedwick, C. — 2008-04-14

Robert Menard: Tailing malaria parasites to the red blood cell

Bashyam, H. — 2008-04-14

The role of CTCF in regulating nuclear organization

Williams, A., Flavell, R. A. — 2008-04-14

The spatial organization of the genome is thought to play an important part in the coordination of gene regulation. New techniques have been used to identify specific long-range interactions between distal DNA sequences, revealing an ever-increasing complexity to nuclear organization. CCCTC-binding factor (CTCF) is a versatile zinc finger protein with diverse regulatory functions. New data now help define how CTCF mediates both long-range intrachromosomal and interchromosomal interactions, and highlight CTCF as an important factor in determining the three-dimensional structure of the genome.

Somatically acquired JAK1 mutations in adult acute lymphoblastic leukemia

2008-04-14

Aberrant signal transduction contributes substantially to leukemogenesis. The Janus kinase 1 (JAK1) gene encodes a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors and plays a nonredundant role in lymphoid cell precursor proliferation, survival, and differentiation. We report that somatic mutations in JAK1 occur in individuals with acute lymphoblastic leukemia (ALL). JAK1 mutations were more prevalent among adult subjects with the T cell precursor ALL, where they accounted for 18% of cases, and were associated with advanced age at diagnosis, poor response to therapy, and overall prognosis. All mutations were missense, and some were predicted to destabilize interdomain interactions controlling the activity of the kinase. Three mutations that were studied promoted JAK1 gain of function and conferred interleukin (IL)-3–independent growth in Ba/F3 cells and/or IL-9–independent resistance to dexamethasone-induced apoptosis in T cell lymphoma BW5147 cells. Such effects were associated with variably enhanced activation of multiple downstream signaling pathways. Leukemic cells with mutated JAK1 alleles shared a gene expression signature characterized by transcriptional up-regulation of genes positively controlled by JAK signaling. Our findings implicate dysregulated JAK1 function in ALL, particularly of T cell origin, and point to this kinase as a target for the development of novel antileukemic drugs.

12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid is a natural ligand for leukotriene B4 receptor 2

Okuno, T., Iizuka, Y., Okazaki, H., Yokomizo, T., Taguchi, R., Shimizu, T. — 2008-04-14

Activated blood platelets and macrophages metabolize prostaglandin H₂ into thromboxane A₂ and 12(S)-hydroxyheptadeca-5Z, 8E, 10E–trienoic acid (12-HHT) in an equimolar ratio through the action of thromboxane synthase. Although it has been shown that 12-HHT is abundant in tissues and bodily fluids, this compound has long been viewed as a by-product lacking any specific function. We show that 12-HHT is a natural ligand for leukotriene B₄ (LTB₄) receptor-2 (BLT2), a G protein–coupled receptor that was originally identified as a low-affinity receptor for LTB₄. BLT2 agonistic activity in lipid fractions from rat small intestine was identified as 12-HHT using high-performance liquid chromatography and mass spectrometry. Exogenously expressed BLT2 in mammalian cells was activated by synthetic 12-HHT, as assessed by guanosine 5'-O-(3-thio) triphosphate binding, the activation of intracellular signaling pathways, and chemotaxis assay. Displacement analysis using [³H]LTB₄ showed that 12-HHT binds to BLT2 with a higher affinity than LTB₄. Lipid extracts from cyclooxygenase 1–deficient mice failed to activate BLT2. Bone marrow–derived mast cells (BMMCs) isolated from wild-type mice migrated toward a low concentration of 12-HHT, whereas BMMCs from BLT2-deficient mice did not. We conclude that 12-HHT is a natural lipid agonist of BLT2 in vivo and induces chemotaxis of mast cells.

Synthetic chemerin-derived peptides suppress inflammation through ChemR23

2008-04-14

Chemerin is a chemotactic protein that binds to the G protein–coupled receptor, ChemR23. We demonstrate that murine chemerin possesses potent antiinflammatory properties that are absolutely dependent on proteolytic processing. A series of peptides was designed, and only those identical to specific C-terminal chemerin sequences exerted antiinflammatory effects at picomolar concentrations in vitro. One of these, chemerin15 (C15; A¹⁴⁰-A¹⁵⁴), inhibited macrophage (M) activation to a similar extent as proteolyzed chemerin, but exhibited reduced activity as a M chemoattractant. Intraperitoneal administration of C15 (0.32 ng/kg) to mice before zymosan challenge conferred significant protection against zymosan-induced peritonitis, suppressing neutrophil (63%) and monocyte (62%) recruitment with a concomitant reduction in proinflammatory mediator expression. Importantly, C15 was unable to ameliorate zymosan-induced peritonitis in ChemR23^–/– mice, demonstrating that C15's antiinflammatory effects are entirely ChemR23 dependent. In addition, administration of neutralizing anti-chemerin antibody before zymosan challenge resulted in a significant exacerbation of peritoneal inflammation (up to 170%), suggesting an important endogenous antiinflammatory role for chemerin-derived species. Collectively, these results show that chemerin-derived peptides may represent a novel therapeutic strategy for the treatment of inflammatory diseases through ChemR23.

CXCR4 is required for the quiescence of primitive hematopoietic cells

Nie, Y., Han, Y.-C., Zou, Y.-R. — 2008-04-14

The quiescence of hematopoietic stem cells (HSCs) is critical for preserving a lifelong steady pool of HSCs to sustain the highly regenerative hematopoietic system. It is thought that specialized niches in which HSCs reside control the balance between HSC quiescence and self-renewal, yet little is known about the extrinsic signals provided by the niche and how these niche signals regulate such a balance. We report that CXCL12 produced by bone marrow (BM) stromal cells is not only the major chemoattractant for HSCs but also a regulatory factor that controls the quiescence of primitive hematopoietic cells. Addition of CXCL12 into the culture inhibits entry of primitive hematopoietic cells into the cell cycle, and inactivation of its receptor CXCR4 in HSCs causes excessive HSC proliferation. Notably, the hyperproliferative Cxcr4^–/– HSCs are able to maintain a stable stem cell compartment and sustain hematopoiesis. Thus, we propose that CXCR4/CXCL12 signaling is essential to confine HSCs in the proper niche and controls their proliferation.

The insulator factor CTCF controls MHC class II gene expression and is required for the formation of long-distance chromatin interactions

Majumder, P., Gomez, J. A., Chadwick, B. P., Boss, J. M. — 2008-04-14

Knockdown of the insulator factor CCCTC binding factor (CTCF), which binds XL9, an intergenic element located between HLA-DRB1 and HLA-DQA1, was found to diminish expression of these genes. The mechanism involved interactions between CTCF and class II transactivator (CIITA), the master regulator of major histocompatibility complex class II (MHC-II) gene expression, and the formation of long-distance chromatin loops between XL9 and the proximal promoter regions of these MHC-II genes. The interactions were inducible and dependent on the activity of CIITA, regulatory factor X, and CTCF. RNA fluorescence in situ hybridizations show that both genes can be expressed simultaneously from the same chromosome. Collectively, the results suggest a model whereby both HLA-DRB1 and HLA-DQA1 loci can interact simultaneously with XL9, and describe a new regulatory mechanism for these MHC-II genes involving the alteration of the general chromatin conformation of the region and their regulation by CTCF.

Either a Th17 or a Th1 effector response can drive autoimmunity: conditions of disease induction affect dominant effector category

2008-04-14

Experimental autoimmune uveitis (EAU) represents autoimmune uveitis in humans. We examined the role of the interleukin (IL)-23–IL-17 and IL-12–T helper cell (Th)1 pathways in the pathogenesis of EAU. IL–23 but not IL-12 was necessary to elicit disease by immunization with the retinal antigen (Ag) interphotoreceptor retinoid-binding protein (IRBP) in complete Freund's adjuvant. IL-17 played a dominant role in this model; its neutralization prevented or reversed disease, and Th17 effector cells induced EAU in the absence of interferon (IFN)-. In a transfer model, however, a polarized Th1 line could induce severe EAU independently of host IL-17. Furthermore, induction of EAU with IRBP-pulsed mature dendritic cells required generation of an IFN-–producing effector response, and an IL-17 response by itself was insufficient to elicit pathology. Finally, genetic deficiency of IL-17 did not abrogate EAU susceptibility. Thus, autoimmune pathology can develop in the context of either a Th17 or a Th1 effector response depending on the model. The data suggest that the dominant effector phenotype may be determined at least in part by conditions present during initial exposure to Ag, including the quality/quantity of Toll-like receptor stimulation and/or type of Ag-presenting cells. These data also raise the possibility that the nonredundant requirement for IL-23 in EAU may extend beyond its role in promoting the Th17 effector response and help provide a balance in the current Th1 versus Th17 paradigm.

The Th17-ELR+ CXC chemokine pathway is essential for the development of central nervous system autoimmune disease

Carlson, T., Kroenke, M., Rao, P., Lane, T. E., Segal, B. — 2008-04-14

The ELR⁺ CXC chemokines CXCL1 and CXCL2 are up-regulated in the central nervous system (CNS) during multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). However, their functional significance and the pathways regulating their expression are largely unknown. We show that transfer of encephalitogenic CD4⁺ Th17 cells is sufficient to induce CXCL1 and CXCL2 transcription in the spinal cords of naive, syngeneic recipients. Blockade or genetic silencing of CXCR2, a major receptor for these chemokines in mice, abrogates blood–brain barrier (BBB) breakdown, CNS infiltration by leukocytes, and the development of clinical deficits during the presentation as well as relapses of EAE. Depletion of circulating polymorphonuclear leukocytes (PMN) had a similar therapeutic effect. Furthermore, injection of CXCR2⁺ PMN into CXCR2^–/– mice was sufficient to restore susceptibility to EAE. Our findings reveal that a Th17–ELR⁺ CXC chemokine pathway is critical for granulocyte mobilization, BBB compromise, and the clinical manifestation of autoimmune demyelination in myelin peptide–sensitized mice, and suggest new therapeutic targets for diseases such as MS.

OX40 triggering blocks suppression by regulatory T cells and facilitates tumor rejection

Piconese, S., Valzasina, B., Colombo, M. P. — 2008-04-14

Regulatory T (T reg) cells are the major obstacle to cancer immunotherapy, and their depletion promptly induces conversion of peripheral precursors into T reg cells. We show that T reg cells can be functionally inactivated by OX40 triggering. In tumors, the vast majority of CD4⁺ T cells are Foxp3⁺ and OX40^bright. However, intratumor injection of the agonist anti-OX40 monoclonal antibody (mAb) OX86, but not anti-CD25 mAb, induces tumor rejection in 80% of mice, an effect that is abrogated by CD8 depletion. Upon intratumor OX40 triggering, increased numbers of infiltrating dendritic cells (DCs) migrate to draining lymph nodes and generate a new wave of tumor-specific cytotoxic T lymphocytes, as detected by tetramer and CD44 staining of node CD8⁺ T lymphocytes. Tumor-bearing Rag1-knockout (KO) mice reconstituted with OX40-deficient T reg cells and wild-type (WT) effector T cells, or the reciprocal combination, showed that both T reg and effector T cells must be triggered via OX40 for the tumor to be rejected. Accordingly, WT but not OX40-KO mice receiving intratumor coinjection of OX86 and ovalbumin protein were able to revert tumor-induced tolerization of adoptively transferred OX40-competent OTII T lymphocytes. In conclusion, OX40-mediated inactivation of T reg cell function unleashes nearby DCs, allowing them to induce an adaptive immune response. In addition, the known OX40-dependent delivery of fitness signals to activated T cells is boosted by concurrent T reg cell inhibition. OX40 triggering thus has multiple effects that converge to mediate tumor rejection.

Polyomavirus BK with rearranged noncoding control region emerge in vivo in renal transplant patients and increase viral replication and cytopathology

2008-04-14

Immunosuppression is required for BK viremia and polyomavirus BK–associated nephropathy (PVAN) in kidney transplants (KTs), but the role of viral determinants is unclear. We examined BKV noncoding control regions (NCCR), which coordinate viral gene expression and replication. In 286 day–matched plasma and urine samples from 129 KT patients with BKV viremia, including 70 with PVAN, the majority of viruses contained archetypal (ww-) NCCRs. However, rearranged (rr-) NCCRs were more frequent in plasma than in urine samples (22 vs. 4%; P < 0.001), and were associated with 20-fold higher plasma BKV loads (2.0 x 10⁴/ml vs. 4.4 x 10⁵/ml; P < 0.001). Emergence of rr-NCCR in plasma correlated with duration and peak BKV load (R² = 0.64; P < 0.001). This was confirmed in a prospective cohort of 733 plasma samples from 227 patients. For 39 PVAN patients with available biopsies, rr-NCCRs were associated with more extensive viral replication and inflammation. Cloning of 10 rr-NCCRs revealed diverse duplications or deletions in different NCCR subregions, but all were sufficient to increase early gene expression, replication capacity, and cytopathology of recombinant BKV in vitro. Thus, rr-NCCR BKV emergence in plasma is linked to increased replication capacity and disease in KTs.

Phospholipase C-{gamma}2 and Vav cooperate within signaling microclusters to propagate B cell spreading in response to membrane-bound antigen

2008-04-14

B cell receptor (BCR) recognition of membrane-bound antigen initiates a spreading and contraction response, the extent of which is controlled through the formation of signaling-active BCR-antigen microclusters and ultimately affects the outcome of B cell activation. We followed a genetic approach to define the molecular requirements of BCR-induced spreading and microcluster formation. We identify a key role for phospholipase C-2 (PLC2), Vav, B cell linker, and Bruton's tyrosine kinase in the formation of highly coordinated "microsignalosomes," the efficient assembly of which is absolutely dependent on Lyn and Syk. Using total internal reflection fluorescence microscopy, we examine at high resolution the recruitment of PLC2 and Vav to microsignalosomes, establishing a novel synergistic relationship between the two. Thus, we demonstrate the importance of cooperation between components of the microsignalosome in the amplification of signaling and propagation of B cell spreading, which is critical for appropriate B cell activation.

Alum adjuvant boosts adaptive immunity by inducing uric acid and activating inflammatory dendritic cells

2008-04-14

Alum (aluminum hydroxide) is the most widely used adjuvant in human vaccines, but the mechanism of its adjuvanticity remains unknown. In vitro studies showed no stimulatory effects on dendritic cells (DCs). In the absence of adjuvant, Ag was taken up by lymph node (LN)–resident DCs that acquired soluble Ag via afferent lymphatics, whereas after injection of alum, Ag was taken up, processed, and presented by inflammatory monocytes that migrated from the peritoneum, thus becoming inflammatory DCs that induced a persistent Th2 response. The enhancing effects of alum on both cellular and humoral immunity were completely abolished when CD11c⁺ monocytes and DCs were conditionally depleted during immunization. Mechanistically, DC-driven responses were abolished in MyD88-deficient mice and after uricase treatment, implying the induction of uric acid. These findings suggest that alum adjuvant is immunogenic by exploiting "nature's adjuvant," the inflammatory DC through induction of the endogenous danger signal uric acid.

Distinct cell-specific control of autoimmunity and infection by Fc{gamma}RIIb

2008-04-14

FcRIIb is an inhibitory Fc receptor expressed on B cells and myeloid cells. It is important in controlling responses to infection, and reduced expression or function predisposes to autoimmunity. To determine if increased expression of FcRIIb can modulate these processes, we created transgenic mice overexpressing FcRIIb on B cells or macrophages. Overexpression of FcRIIb on B cells reduced the immunoglobulin G component of T-dependent immune responses, led to early resolution of collagen-induced arthritis (CIA), and reduced spontaneous systemic lupus erythematosus (SLE). In contrast, overexpression on macrophages had no effect on immune responses, CIA, or SLE but increased mortality after Streptococcus pneumoniae infection. These results help define the role of FcRIIb in immune responses, demonstrate the contrasting roles played by FcRIIb on B cells and macrophages in the control of infection and autoimmunity, and emphasize the therapeutic potential for modulation of FcRIIb expression on B cells in inflammatory and autoimmune disease.

IL-9- and mast cell-mediated intestinal permeability predisposes to oral antigen hypersensitivity

2008-04-14

Previous mouse and clinical studies demonstrate a link between Th2 intestinal inflammation and induction of the effector phase of food allergy. However, the mechanism by which sensitization and mast cell responses occurs is largely unknown. We demonstrate that interleukin (IL)-9 has an important role in this process. IL-9–deficient mice fail to develop experimental oral antigen–induced intestinal anaphylaxis, and intestinal IL-9 overexpression induces an intestinal anaphylaxis phenotype (intestinal mastocytosis, intestinal permeability, and intravascular leakage). In addition, intestinal IL-9 overexpression predisposes to oral antigen sensitization, which requires mast cells and increased intestinal permeability. These observations demonstrate a central role for IL-9 and mast cells in experimental intestinal permeability in oral antigen sensitization and suggest that IL-9–mediated mast cell responses have an important role in food allergy.

Interaction of CD44 and hyaluronan is the dominant mechanism for neutrophil sequestration in inflamed liver sinusoids

2008-04-14

Adhesion molecules known to be important for neutrophil recruitment in many other organs are not involved in recruitment of neutrophils into the sinusoids of the liver. The prevailing view is that neutrophils become physically trapped in inflamed liver sinusoids. In this study, we used a biopanning approach to identify hyaluronan (HA) as disproportionately expressed in the liver versus other organs under both basal and inflammatory conditions. Spinning disk intravital microscopy revealed that constitutive HA expression was restricted to liver sinusoids. Blocking CD44–HA interactions reduced neutrophil adhesion in the sinusoids of endotoxemic mice, with no effect on rolling or adhesion in postsinusoidal venules. Neutrophil but not endothelial CD44 was required for adhesion in sinusoids, yet neutrophil CD44 avidity for HA did not increase significantly in endotoxemia. Instead, activation of CD44–HA engagement via qualitative modification of HA was demonstrated by a dramatic induction of serum-derived HA-associated protein in sinusoids in response to lipopolysaccharide (LPS). LPS-induced hepatic injury was significantly reduced by blocking CD44–HA interactions. Administration of anti-CD44 antibody 4 hours after LPS rapidly detached adherent neutrophils in sinusoids and improved sinusoidal perfusion in endotoxemic mice, revealing CD44 as a potential therapeutic target in systemic inflammatory responses involving the liver.

Gene placement and competition control T cell receptor {gamma} variable region gene rearrangement

Xiong, N., Zhang, L., Kang, C., Raulet, D. H. — 2008-04-14

The production of distinct sets of T cell receptor (TCR) ⁺ T cells occurs in an ordered fashion in thymic development. The V3 and V4 genes, located downstream in the TCR C1 gene cluster, are expressed by the earliest waves of developing TCR⁺ T cells in the fetal thymus, destined for intraepithelial locations. Upstream V2 and V5 genes are expressed in later waves in the adult and constitute most TCR⁺ T cells in secondary lymphoid tissue. This developmental pattern is caused in part by a preference for rearrangements of the downstream V3 and V4 genes in the early fetal stage, which switches to a preference for rearrangements of the upstream V2 and V5 gene rearrangements in the adult. Our gene targeting studies show that the downstream V genes rearrange preferentially in the early fetal thymus because of their downstream location, independent of promoter or recombination signal sequences and unrelated to the extent of germline transcription. Remarkably, gene deletion studies show that the downstream V genes competitively inhibit upstream V rearrangements at the fetal stage. These data provide a mechanism for specialization of the fetal thymus for the production of T cells expressing specific V genes.

A minimal binding footprint on CD1d-glycolipid is a basis for selection of the unique human NKT TCR

2008-04-14

Although it has been established how CD1 binds a variety of lipid antigens (Ag), data are only now emerging that show how β T cell receptors (TCRs) interact with CD1-Ag. Using the structure of the human semiinvariant NKT TCR–CD1d–-galactosylceramide (-GalCer) complex as a guide, we undertook an alanine scanning mutagenesis approach to define the energetic basis of this interaction between the NKT TCR and CD1d. Moreover, we explored how analogues of -GalCer affected this interaction. The data revealed that an identical energetic footprint underpinned the human and mouse NKT TCR–CD1d–-GalCer cross-reactivity. Some, but not all, of the contact residues within the J18-encoded invariant CDR3 loop and Vβ11-encoded CDR2β loop were critical for recognizing CD1d. The residues within the V24-encoded CDR1 and CDR3 loops that contacted the glycolipid Ag played a smaller energetic role compared with the NKT TCR residues that contacted CD1d. Collectively, our data reveal that the region distant to the protruding Ag and directly above the F' pocket of CD1d was the principal factor in the interaction with the NKT TCR. Accordingly, although the structural footprint at the NKT TCR–CD1d–-GalCer is small, the energetic footprint is smaller still, and reveals the minimal requirements for CD1d restriction.

Leukocyte transmigration requires kinesin-mediated microtubule-dependent membrane trafficking from the lateral border recycling compartment

Mamdouh, Z., Kreitzer, G. E., Muller, W. A. — 2008-04-14

Diapedesis of leukocytes across endothelial cells is a crucial step in both the innate and adaptive immune responses. Surface molecules on leukocytes and endothelial cells critical for diapedesis have been identified, but the mechanisms underlying this process are not understood. Homophilic interaction between platelet/endothelial cell adhesion molecule (PECAM) on leukocytes and PECAM at the endothelial border triggers targeted recycling of membrane from a reticulum localized close to the endothelial cell lateral border. This membrane surrounds the transmigrating leukocyte (Mamdouh, Z., X. Chen, L.M. Pierini, F.R. Maxfield, and W.A. Muller. 2003. Nature. 421:748–753). How this process occurs and whether it is required for diapedesis independent of PECAM are not known. We now report that targeted recycling from this lateral border recycling compartment (LBRC) is required for diapedesis, is mediated by kinesin family molecular motors, and requires normally functioning endothelial microtubules. Selective disruption of microtubules or inhibition of kinesin motor domain blocked targeted recycling and diapedesis of monocytes. Furthermore, targeted recycling of membrane from the LBRC was required for transmigration of lymphocytes, which migrate independently of PECAM. Thus, trafficking of membrane from the LBRC to surround leukocytes may be a general requirement for migration of leukocytes across the endothelial cell border. Furthermore, these data provide the first demonstration of a role for endothelial microtubules and kinesins in promoting diapedesis, and a mechanism to explain targeted recycling.

Arthritis induced by posttranslationally modified (citrullinated) fibrinogen in DR4-IE transgenic mice

2008-04-14

Rheumatoid arthritis (RA) is a common autoimmune disease that afflicts the synovium of diarthrodial joints. The pathogenic mechanisms inciting this disease are not fully characterized, but may involve the loss of tolerance to posttranslationally modified (citrullinated) antigens. We have demonstrated that this modification leads to a selective increase in antigenic peptide affinity for major histocompatibility complex (MHC) class II molecules that carry the RA-associated shared epitope, such as HLA-DRB1*0401 (DR4). We describe the induction of arthritis in DR4-IE transgenic (tg) mice with citrullinated fibrinogen, a protein commonly found in inflamed synovial tissue and a frequent target of autoantibodies in RA patients. The disease induced in these mice was characterized by synovial hyperplasia followed by ankylosis, but lacked a conspicuous polymorphonuclear cell infiltrate. Immunological analysis of these mice through T cell epitope scanning and antibody microarray analysis identified a unique profile of citrulline-specific reactivity that was not found in DR4-IE tg mice immunized with unmodified fibrinogen or in wild-type C57BL/6 mice immunized with citrullinated fibrinogen, two conditions where arthritis was not observed. These observations directly implicate citrullinated fibrinogen as arthritogenic in the context of RA-associated MHC class II molecules.

The orthopoxvirus type I IFN binding protein is essential for virulence and an effective target for vaccination

2008-04-14

Nonliving antiviral vaccines traditionally target proteins expressed at the surface of the virion with the hope of inducing neutralizing antibodies. Orthopoxviruses (OPVs), such as the human smallpox virus and the mouse-equivalent ectromelia virus (ECTV; an agent of mousepox), encode immune response modifiers (IRMs) that can increase virulence by decreasing the host immune response. We show that one of these IRMs, the type I interferon (IFN) binding protein (bp) of ECTV, is essential for ECTV virulence and is a natural target of the antibody response. More strikingly, we demonstrate that immunization with recombinant type I IFN bp protects mice from lethal mousepox. Collectively, our experiments have important implications for our understanding of the role of IRMs in OPV virulence and of type I IFNs in OPV infections. Furthermore, our work provides proof of concept that effective antiviral vaccines can be made to prevent disease by targeting virulence factors as an alternative to the traditional approach that attempts to prevent infection by virus neutralization.

Nonmuscle myosin heavy chain IIA mediates integrin LFA-1 de-adhesion during T lymphocyte migration

2008-04-14

Myoblasts and macrophages share molecular components that contribute to cell-cell fusion

Pajcini, K. V., Pomerantz, J. H., Alkan, O., Doyonnas, R., Blau, H. M. — 2008-03-17

Inhibition of "self" engulfment through deactivation of myosin-II at the phagocytic synapse between human cells

Tsai, R. K., Discher, D. E. — 2008-03-17

Disadvantages of a SPARCling defense

Bashyam, H. — 2008-03-17

Less naive with age

Bashyam, H. — 2008-03-17

Regulatory T cell brakes

Bashyam, H. — 2008-03-17

Clotting linked to a memory maker

Bashyam, H. — 2008-03-17

Granules live and let die

Bashyam, H. — 2008-03-17

Michael T. McManus: Interrupting biology

Bashyam, H. — 2008-03-17

Fixing DNA breaks during class switch recombination

Jolly, C. J., Cook, A. J.L., Manis, J. P. — 2008-03-17

Immunoglobulin (Ig) class switch recombination (CSR) involves the breakage and subsequent repair of two DNA sequences, known as switch (S) regions, which flank IgH constant region exons. The resolution of CSR-associated breaks is thought to require the nonhomologous end-joining (NHEJ) DNA repair pathway, but the role of the NHEJ factor DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in this process has been unclear. A new study, in which broken IgH-containing chromosomes in switching B cells were visualized directly, clearly demonstrated that DNA-PKcs and, unexpectedly, the nuclease Artemis are involved in the resolution of switch breaks.