bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor Necrosis Factor Receptor–associated Factor 6 (TRAF6) Stimulates Extracellular Signal–regulated Kinase (ERK) Activity in CD40 Signaling Along a Ras-independent Pathway
Authors: Kashiwada Masaki , Shirakata Yumiko , Inoue Jun-Ichiro , Nakano Hiroyasu , Okazaki Kenji , Okumura Ko , Yamamoto Tadashi , Nagaoka Hitoshi , Takemori Toshitada
Published: July 2002

CD40 activates nuclear factor kappa B (NFκB) and the mitogen-activated protein kinase (MAPK) subfamily, including extracellular signal–regulated kinase (ERK). The CD40 cytoplasmic tail interacts with tumor necrosis factor receptor–associated factor (TRAF)2, TRAF3, TRAF5, and TRAF6. These TRAF proteins, with the exception of TRAF3, are required for NFκB activation. Here we report that transient expression of TRAF6 stimulated both ERK and NFκB activity in the 293 cell line. Coexpression of the dominant-negative H-Ras did not affect TRAF6-mediated ERK activity, suggesting that TRAF6 may activate ERK along a Ras-independent pathway. The deletion mutant of TRAF6 lacking the NH2-terminal domain acted as a dominant-negative mutant to suppress ERK activation by full-length CD40 and suppress prominently ERK activation by a deletion mutant of CD40 only containing the binding site for TRAF6 in the cytoplasmic tail (CD40Δ246). Transient expression of the dominant-negative H-Ras significantly suppressed ERK activation by full-length CD40, but marginally suppressed ERK activation by CD40Δ246, compatible with the possibility that TRAF6 is a major transducer of ERK activation by CD40Δ246, whose activity is mediated by a Ras-independent pathway. These results suggest that CD40 activates ERK by both a Ras-dependent pathway and a Ras-independent pathway in which TRAF6 could be involved.
Interleukin 10 Increases CCR5 Expression and HIV Infection in Human Monocytes
Authors: Sozzani Silvano , Ghezzi Silvia , Iannolo Gioacchino , Luini Walter , Borsatti Alessandro , Polentarutti Nadia , Sica Antonio , Locati Massimo , Mackay Charles , Wells Timothy N.C. , Biswas Priscilla , Vicenzi Elisa , Poli Guido , Mantovani Alberto
Published: July 2002

The immunosuppressive and antiinflammatory cytokine interleukin (IL) 10 selectively upregulates the expression of the CC chemokine receptors CCR5, 2, and 1 in human monocytes by prolonging their mRNA half-life. IL-10–stimulated monocytes display an increased number of cell surface receptors for, and better chemotactic responsiveness to, relevant agonists than do control cells. In addition, IL-10–stimulated monocytes are more efficiently infected by HIV BaL. This effect was associated to the enhancement of viral entry through CCR5. These data add support to an emerging paradigm in which pro- and antiinflammatory molecules exert reciprocal and opposing influence on chemokine agonist production and receptor expression.
Efficient Presentation of Phagocytosed Cellular Fragments on the Major Histocompatibility Complex Class II Products of Dendritic Cells
Authors: Inaba Kayo , Turley Shannon , Yamaide Fumiya , Iyoda Tomonori , Mahnke Karsten , Inaba Muneo , Pack Margit , Subklewe Marion , Sauter Birthe , Sheff David , Albert Matthew , Bhardwaj Nina , Mellman Ira , Steinman Ralph M.
Published: July 2002

Cells from the bone marrow can present peptides that are derived from tumors, transplants, and self-tissues. Here we describe how dendritic cells (DCs) process phagocytosed cell fragments onto major histocompatibility complex (MHC) class II products with unusual efficacy. This was monitored with the Y-Ae monoclonal antibody that is specific for complexes of I-Ab MHC class II presenting a peptide derived from I-Eα. When immature DCs from I-Ab mice were cultured for 5–20 h with activated I-E+ B blasts, either necrotic or apoptotic, the DCs produced the epitope recognized by the Y-Ae monoclonal antibody and stimulated T cells reactive with the same MHC–peptide complex. Antigen transfer was also observed with human cells, where human histocompatibility leukocyte antigen (HLA)-DRα includes the same peptide sequence as mouse I-Eα. Antigen transfer was preceded by uptake of B cell fragments into MHC class II–rich compartments. Quantitation of the amount of I-E protein in the B cell fragments revealed that phagocytosed I-E was 1–10 thousand times more efficient in generating MHC–peptide complexes than preprocessed I-E peptide. When we injected different I-E– bearing cells into C57BL/6 mice to look for a similar phenomenon in vivo, we found that short-lived migrating DCs could be processed by most of the recipient DCs in the lymph node. The consequence of antigen transfer from migratory DCs to lymph node DCs is not yet known, but we suggest that in the steady state, i.e., in the absence of stimuli for DC maturation, this transfer leads to peripheral tolerance of the T cell repertoire to self.
Interleukin 6 Dependence of Anti-DNA Antibody Production: Evidence for Two Pathways of Autoantibody Formation in Pristane-induced Lupus
Authors: Richards Hanno B. , Satoh Minoru , Shaw Melody , Libert Claude , Poli Valeria , Reeves Westley H.
Published: July 2002

Pristane induces a lupus-like syndrome in nonautoimmune mice characterized by the development of glomerulonephritis and lupus-associated autoantibodies. This is accompanied by overproduction of interleukin (IL)-6, a cytokine linked with autoimmune phenomena. The goal of this study was to evaluate the role of IL-6 in autoantibody production in pristane-induced lupus. BALB/cAn IL-6–deficient (−/−) and –intact (+/+) mice were treated with pristane or phosphate-buffered saline, and autoantibody production was evaluated. Pristane induced high levels of immunoglobulin (Ig)G anti-single-stranded DNA, –double-stranded (ds)DNA, and -chromatin antibodies in IL-6+/+, but not IL-6−/− mice by enzyme-linked immunosorbent assay. High titer IgG anti-dsDNA antibodies also were detected in sera from +/+, but not −/−, mice by Crithidia luciliae kinetoplast staining. The onset of IgG anti-dsDNA antibody production in +/+ mice occurred >5 mo after pristane treatment, well after the onset of nephritis, suggesting that these antibodies are not directly responsible for inducing renal disease. In contrast to anti-DNA, the frequencies of anti-nRNP/Sm and anti-Su antibodies were similar in pristane-treated IL-6−/− and IL-6+/+ mice. However, levels were higher in the +/+ group. These results suggest that IgG anti-DNA and chromatin antibodies in pristane-treated mice are strictly IL-6 dependent, whereas induction of anti-nRNP/Sm and Su autoantibodies is IL-6 independent. The IL-6 dependence of anti-DNA, but not anti-nRNP/Sm, may have implications for understanding the patterns of autoantibody production in lupus. Anti-DNA antibodies are produced transiently, mainly during periods of disease activity, whereas anti-nRNP/Sm antibody levels are relatively insensitive to disease activity. This may reflect the differential IL-6 dependence of the two responses.
Fas and Fas Ligand Interactions Suppress Melanoma Lung Metastasis
Authors: Owen-Schaub Laurie B. , van Golen Kenneth L. , Hill Laurie L. , Price Janet E.
Published: July 2002

Apoptosis induced by Fas (CD95) ligation is frequently lost during tumor progression; however, there is no direct evidence to support an association of Fas loss-of-function with metastatic tumor behavior. To determine whether Fas loss-of-function is critical for acquisition of the metastatic phenotype, we have compared the ability of Fas-sensitive K1735 murine melanomas to form spontaneous lung metastases in wild-type and Fas ligand–deficient mice. Fas-sensitive melanoma clones are highly tumorigenic but rarely metastatic in wild-type syngeneic mice. However, in Fas ligand–deficient mice, both the incidence and number of metastases are increased. These findings provide the first evidence that Fas–Fas ligand interactions can suppress metastasis and that tumor Fas loss-of-function may be causally linked to metastatic progression.
Distinct Subsets of CD1d-restricted T Cells Recognize Self-antigens Loaded in Different Cellular Compartments
Authors: Chiu Ya-Hui , Jayawardena Jayanthi , Weiss Angela , Lee Daniel , Park Se-Ho , Dautry-Varsat Alice , Bendelac Albert
Published: July 2002

Although recent studies have indicated that the major histocompatibility complex–like, β2-microglobulin–associated CD1 molecules might function to present a novel chemical class of antigens, lipids and glycolipids, to α/β T cells, little is known about the T cell subsets that interact with CD1. A subset of CD1d-autoreactive, natural killer (NK)1.1 receptor–expressing α/β T cells has recently been identified. These cells, which include both CD4−CD8− and CD4+ T cells, preferentially use an invariant Vα14-Jα281 T cell receptor (TCR) α chain paired with a Vβ8 TCR β chain in mice, or the homologous Vα24-JαQ/Vβ11 in humans. This cell subset can explosively release key cytokines such as interleukin (IL)-4 and interferon (IFN)-γ upon TCR engagement and may regulate a variety of infectious and autoimmune conditions. Here, we report the existence of a second subset of CD1d-restricted CD4+ T cells that do not express the NK1.1 receptor or the Vα14 TCR. Like the Vα14+ NK1.1+ T cells, these T cells exhibit a high frequency of autoreactivity to CD1d, use a restricted albeit distinct set of TCR gene families, and contribute to the early burst of IL-4 and IFN-γ induced by intravenous injection of anti-CD3. However, the Vα14+ NK1.1+ and Vα14− NK1.1− T cells differ markedly in their requirements for self-antigen presentation. Antigen presentation to the Vα14+ NK1.1+ cells requires endosomal targeting of CD1d through a tail-encoded tyrosine-based motif, whereas antigen presentation to the Vα14− NK1.1− cells does not. These experiments suggest the existence of two phenotypically different subsets of CD1d-restricted T cells that survey self-antigens loaded in distinct cellular compartments.
Natural Killer Cell–mediated Lysis of Autologous Cells Modified by Gene Therapy
Authors: Liberatore Concetta , Capanni Marusca , Albi Nicola , Volpi Isabella , Urbani Elena , Ruggeri Loredana , Mencarelli Amedea , Grignani Francesco , Velardi Andrea
Published: July 2002

This study investigated the role of natural killer (NK) cells as effectors of an immune response against autologous cells modified by gene therapy. T lymphocytes were transduced with LXSN, a retroviral vector adopted for human gene therapy that carries the selectable marker gene neo, and the autologous NK response was evaluated. We found that (i) infection with LXSN makes cells susceptible to autologous NK cell–mediated lysis; (ii) expression of the neo gene is responsible for conferring susceptibility to lysis; (iii) lysis of neo-expressing cells is clonally distributed and mediated only by NK clones that exhibit human histocompatibility leukocyte antigen (HLA)-Bw4 specificity and bear KIR3DL1, a Bw4-specific NK inhibitory receptor; and (iv) the targets are cells from HLA-Bw4+ individuals. Finally, neo peptides anchoring to the Bw4 allele HLA-B27 interfered with KIR3DL1-mediated recognition of HLA-B27, i.e., they triggered NK lysis. Moreover, neo gene mutations preventing translation of  two of the four potentially nonprotective peptides reduced KIR3DL1+ NK clone–mediated autologous lysis. Thus, individuals expressing Bw4 alleles possess an NK repertoire with the potential to eliminate autologous cells modified by gene therapy. By demonstrating that NK cells can selectively detect the expression of heterologous genes, these observations provide a general model of the NK cell–mediated control of viral infections.
Mice Lacking Expression of Secondary Lymphoid Organ Chemokine Have Defects in Lymphocyte Homing and Dendritic Cell Localization
Authors: Gunn Michael D. , Kyuwa Shigeru , Tam Carmen , Kakiuchi Terutaka , Matsuzawa Akio , Williams Lewis T. , Nakano Hideki
Published: July 2002

Secondary lymphoid organ chemokine (SLC) is expressed in high endothelial venules and in T cell zones of spleen and lymph nodes (LNs) and strongly attracts naive T cells. In mice homozygous for the paucity of lymph node T cell (plt) mutation, naive T cells fail to home to LNs or the lymphoid regions of spleen. Here we demonstrate that expression of SLC is undetectable in plt mice. In addition to the defect in T cell homing, we demonstrate that dendritic cells (DCs) fail to accumulate in spleen and LN T cell zones of plt mice. DC migration to LNs after contact sensitization is also substantially reduced. The physiologic significance of these abnormalities in plt mice is indicated by a markedly increased sensitivity to infection with murine hepatitis virus. The plt mutation maps to the SLC locus; however, the sequence of SLC introns and exons in plt mice is normal. These findings suggest that the abnormalities in plt mice are due to a genetic defect in the expression of SLC and that SLC mediates the entry of naive T cells and antigen-stimulated DCs into the T cell zones of secondary lymphoid organs.
Immune Responses to Ro60 and Its Peptides in Mice. I.  The Nature of the Immunogen and Endogenous Autoantigen Determine the Specificities of the Induced Autoantibodies
Authors: Deshmukh Umesh S. , Lewis Janet E. , Gaskin Felicia , Kannapell Carol C. , Waters Samuel T. , Lou Ya-huan , Tung Kenneth S.K. , Fu Shu Man
Published: July 2002

Anti-Ro60 autoantibodies are found in a variety of autoimmune disorders including systemic lupus erythematosus (SLE), Sjögren's syndrome, primary biliary cirrhosis, and active hepatitis. They are the most prevalent autoantibodies in normal individuals and in asymptomatic mothers of infants afflicted with neonatal lupus. In the present study, immune responses to recombinant human Ro60 (rhRo60) and recombinant mouse Ro60 (rmRo60) and selected Ro60 peptides in non–SLE-prone mice were investigated. Multiple T and B cell epitopes were identified in Ro60. Immunizations with either xenogeneic or autologous Ro60 induced autoantibodies to a diverse group of autoantigens. In addition to La and Ro52, proteins in the small nuclear ribonucleoprotein (snRNP) particles such as SmA, SmB, SmD, and 70-kD U1-RNP were unexpectedly identified as targeted antigens. In the studies involving synthetic Ro60 peptides, both human and mouse Ro60316–335 peptides, which differ in three amino acids, were found to contain dominant cross-reactive T cell determinants. Immunizations with these peptides induced autoantibodies to Ro60, La, SmD, and 70-kD U1-RNP without autoantibodies to Ro52, SmA, or SmB. With human Ro60316–335 as the immunogen, additional autoantibodies reactive with the Golgi complex were found. In contrast to the immunodominance of both human and mouse Ro60316–335 peptides, the T cell determinant in human Ro60441–465 was dominant, whereas that in the mouse peptide was cryptic. Immunization with human Ro60441–465 induced primarily anti-peptide Abs. Mouse Ro60441–465 failed to induce an antibody response. These results show that both the nature of the immunogen and the immunogenicity of the related endogenous antigen are important in determining the specificities of the autoantibodies generated. They have significant implications for proposed mechanisms on the generation of complex patterns of autoantibodies to a diverse group of autoantigens in SLE patients.
Altered Ligands Reveal Limited Plasticity in the T Cell Response to a Pathogenic Epitope
Authors: Pingel Sabine , Launois Pascal , Fowell Deborah J. , Turck Christoph W. , Southwood Scott , Sette Alessandro , Glaichenhaus Nicolas , Louis Jacques A. , Locksley Richard M.
Published: July 2002

Experimental leishmaniasis offers a well characterized model of T helper type 1 cell (Th1)-mediated control of infection by an intracellular organism. Susceptible BALB/c mice aberrantly develop Th2 cells in response to infection and are unable to control parasite dissemination. The early CD4+ T cell response in these mice is oligoclonal and reflects the expansion of Vβ4/ Vα8-bearing T cells in response to a single epitope from the parasite Leishmania homologue of mammalian RACK1 (LACK) antigen. Interleukin 4 (IL-4) generated by these cells is believed to direct the subsequent Th2 response. We used T cells from T cell receptor–transgenic mice expressing such a Vβ4/Vα8 receptor to characterize altered peptide ligands with similar affinity for I-Ad. Such altered ligands failed to activate IL-4 production from transgenic LACK-specific T cells or following injection into BALB/c mice. Pretreatment of susceptible mice with altered peptide ligands substantially altered the course of subsequent infection. The ability to confer a healer phenotype on otherwise susceptible mice using altered peptides that differed by a single amino acid suggests limited diversity in the endogenous T cell repertoire recognizing this antigen.
Dendritic Cells Discriminate between Yeasts and Hyphae of the Fungus Candida albicans
Authors: d'Ostiani Cristiana Fè , Del Sero Giuseppe , Bacci Angela , Montagnoli Claudia , Spreca Antonio , Mencacci Antonella , Ricciardi-Castagnoli Paola , Romani Luigina
Published: July 2002

The fungus Candida albicans behaves as a commensal as well as a true pathogen of areas highly enriched in dendritic cells, such as skin and mucosal surfaces. The ability of the fungus to reversibly switch between unicellular yeast to filamentous forms is thought to be important for virulence. However, whether it is the yeast or the hyphal form that is responsible for pathogenicity is still a matter of debate. Here we show the interaction, and consequences, of different forms of C. albicans with dendritic cells. Immature myeloid dendritic cells rapidly and efficiently phagocytosed both yeasts and hyphae of the fungus. Phagocytosis occurred through different phagocytic morphologies and receptors, resulting in phagosome formation. However, hyphae escaped the phagosome and were found lying free in the cytoplasm of the cells. In vitro, ingestion of yeasts activated dendritic cells for interleukin (IL)-12 production and priming of T helper type 1 (Th1) cells, whereas ingestion of hyphae inhibited IL-12 and Th1 priming, and induced IL-4 production. In vivo, generation of antifungal protective immunity was induced upon injection of dendritic cells ex vivo pulsed with Candida yeasts but not hyphae. The immunization capacity of yeast-pulsed dendritic cells was lost in the absence of IL-12, whereas that of hypha-pulsed dendritic cells was gained in the absence of IL-4. These results indicate that dendritic cells fulfill the requirement of a cell uniquely capable of sensing the two forms of C. albicans in terms of type of immune responses elicited. By the discriminative production of IL-12 and IL-4 in response to the nonvirulent and virulent forms of the fungus, dendritic cells appear to meet the challenge of Th priming and education in C. albicans saprophytism and infections.
Coupling of Peripheral Tolerance to Endogenous Interleukin 10 Promotes Effective Modulation of Myelin-Activated T Cells and Ameliorates Experimental Allergic Encephalomyelitis
Authors: Legge Kevin L. , Min Booki , Bell J. Jeremiah , Caprio Jacque C. , Li Lequn , Gregg Randal K. , Zaghouani Habib
Published: July 2002

Several immune-based approaches are being considered for modulation of inflammatory T cells and amelioration of autoimmune diseases. The most recent strategies include simulation of peripheral self-tolerance by injection of adjuvant free antigen, local delivery of cytokines by genetically altered T cells, and interference with the function of costimulatory molecules. Although promising results have been obtained from these studies that define mechanisms of T cell modulation, efficacy, practicality, and toxicity, concerns remain unsolved, thereby justifying further investigations to define alternatives for effective downregulation of aggressive T cells. In prior studies, we demonstrated that an immunoglobulin (Ig) chimera carrying the encephalitogenic proteolipid protein (PLP)1 peptide corresponding to amino acid sequence 139–151 of PLP, Ig-PLP1, is presented to T cells ∼100-fold better than free PLP1. Here, we demonstrate that aggregation endows Ig-PLP1 with an additional feature, namely, induction of interleukin (IL)-10 production by macrophages and dendritic cells, both of which are antigen-presenting cells (APCs). These functions synergize in vivo and drive effective modulation of autoimmunity. Indeed, it is shown that animals with ongoing active experimental allergic encephalomyelitis dramatically reduce the severity of their paralysis when treated with adjuvant free aggregated Ig-PLP1. Moreover, IL-10 displays bystander antagonism on unrelated autoreactive T cells, allowing for reversal of disease involving multiple epitopes. Therefore, aggregated Ig-PLP1 likely brings together a peripheral T cell tolerance mechanism emanating from peptide presentation by APCs expressing suboptimal costimulatory molecules and IL-10 bystander suppression to drive a dual-modal T cell modulation system effective for reversal of autoimmunity involving several epitopes and diverse T cell specificities.
Initiation of Apoptosis by Granzyme B Requires Direct Cleavage of Bid, but Not Direct Granzyme B–Mediated Caspase Activation
Authors: Sutton Vivien R. , Davis Joanne E. , Cancilla Michael , Johnstone Ricky W. , Ruefli Astrid A. , Sedelies Karin , Browne Kylie A. , Trapani Joseph A.
Published: July 2002

The essential upstream steps in granzyme B–mediated apoptosis remain undefined. Herein, we show that granzyme B triggers the mitochondrial apoptotic pathway through direct cleavage of Bid; however, cleavage of procaspases was stalled when mitochondrial disruption was blocked by Bcl-2. The sensitivity of granzyme B–resistant Bcl-2–overexpressing FDC-P1 cells was restored by coexpression of wild-type Bid, or Bid with a mutation of its caspase-8 cleavage site, and both types of Bid were cleaved. However, Bid with a mutated granzyme B cleavage site remained intact and did not restore apoptosis. Bid with a mutation preventing its interaction with Bcl-2 was cleaved but also failed to restore apoptosis. Rapid Bid cleavage by granzyme B (<2 min) was not delayed by Bcl-2 overexpression. These results clearly placed Bid cleavage upstream of mitochondrial Bcl-2. In granzyme B–treated Jurkat cells, endogenous Bid cleavage and loss of mitochondrial membrane depolarization occurred despite caspase inactivation with z-Val-Ala-Asp-fluoromethylketone or Asp-Glu-Val-Asp-fluoromethylketone. Initial partial processing of procaspase-3 and -8 was observed irrespective of Bcl-2 overexpression; however, later processing was completely abolished by Bcl-2. Overall, our results indicate that mitochondrial perturbation by Bid is necessary to achieve a lethal threshold of caspase activity and cell death due to granzyme B.
Uncoupling the Proinflammatory from the Immunosuppressive Properties of Tumor Necrosis Factor (Tnf) at the P55 TNF Receptor Level
Authors: Kassiotis George , Kollias George
Published: July 2002

Multiple sclerosis (MS) is a disabling inflammatory demyelinating disease of the central nervous system, considered to result from self-reactivity to myelin antigens. Tumor necrosis factor (TNF) and the p55 TNF receptor (TNFR) have been strongly implicated in MS pathogenesis. We reveal in this study a dual role for TNF in experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. In addition to its well-established proinflammatory effects, TNF exhibits potent immunosuppressive properties, providing one possible explanation for the immune and disease activating effect of anti-TNF treatment of MS. We show that in TNF-deficient mice, myelin-specific T cell reactivity fails to regress and expansion of activated/memory T cells is abnormally prolonged, leading to exacerbated EAE. Strikingly, immnosuppression by TNF and protection against EAE does not require the p55 TNFR, whereas the same receptor is necessary for the detrimental effects of TNF during the acute phase of the disease. Thus, blocking the function of the p55 TNFR in autoimmune demyelination may inhibit the noxious proinflammatory activities of TNF without compromising its immunosuppressive properties.
Cytokines Regulate Proteolysis in Major Histocompatibility Complex Class II–Dependent Antigen Presentation by Dendritic Cells
Authors: Fiebiger Edda , Meraner Paul , Weber Ekkehard , Fang I-Fei , Stingl Georg , Ploegh Hidde , Maurer Dieter
Published: July 2002

Endo/lysosomal proteases control two key events in antigen (Ag) presentation: the degradation of protein Ag and the generation of peptide-receptive major histocompatibility complex (MHC) class II molecules. Here we show that the proinflammatory cytokines tumor necrosis factor α and interleukin (IL)-1β rapidly increase the activity of cathepsin (cat) S and catB in human dendritic cells (DCs). As a consequence, a wave of MHC class II sodium dodecyl sulfate stable dimer formation ensues in a catS-dependent fashion. In contrast, the antiinflammatory cytokine IL-10 renders DCs incapable of upregulating catS and catB activity and in fact, attenuates the level of both enzymes. Suppressed catS and catB activity delays MHC class II sodium dodecyl sulfate stable dimer formation and impairs Ag degradation. In DCs exposed to tetanus toxoid, IL-10 accordingly reduces the number of MHC class II–peptide complexes accessible to tetanus toxoid–specific T cell receptors, as analyzed by measuring T cell receptor downregulation in Ag-specific T cell clones. Thus, the control of protease activity by pro- and antiinflammatory cytokines is an essential feature of the Ag presentation properties of DCs.
Splenic T Zone Development Is B Cell Dependent
Authors: Ngo Vu N. , Cornall Richard J. , Cyster Jason G.
Published: July 2002

The factors regulating growth and patterning of the spleen are poorly defined. We demonstrate here that spleens from B cell–deficient mice have 10-fold reduced expression of the T zone chemokine, CCL21, a threefold reduction in T cell and dendritic cell (DC) numbers, and reduced expression of the T zone stromal marker, gp38. Using cell transfer and receptor blocking approaches, we provide evidence that B cells play a critical role in the early postnatal development of the splenic T zone. This process involves B cell expression of lymphotoxin (LT)α1β2, a cytokine that is required for expression of CCL21 and gp38. Introduction of a B cell specific LTα transgene on to the LTα-deficient background restored splenic CCL21 and gp38 expression, DC numbers, and T zone size. This work also demonstrates that the role of B cells in T zone development is distinct from the effect of B cells on splenic T cell numbers, which does not require LTα1β2. Therefore, B cells influence spleen T zone development by providing: (a) signals that promote T cell accumulation, and: (b) signals, including LTα1β2, that promote stromal cell development and DC accumulation. Defects in these parameters may contribute to the immune defects associated with B cell deficiency in mice and humans.
The Biological Activity of Natural and Mutant Ptα Alleles
Authors: Gibbons Deena , Douglas Nataki C. , Barber Domingo F. , Liu Qiang , Sullo Renee , Geng Liping , Fehling Hans-Joerg , von Boehmer Harald , Hayday Adrian C.
Published: July 2002

β selection is a major checkpoint in early thymocyte differentiation, mediated by successful expression of the pre-T cell receptor (TCR) comprising the TCRβ chain, CD3 proteins, and a surrogate TCRα chain, pTα. The mechanism of action of the pre-TCR is unresolved. In humans and mice, the pTα gene encodes two RNAs, pTαa, and a substantially truncated form, pTαb. This study shows that both are biologically active in their capacity to rescue multiple thymocyte defects in pTα−/− mice. Further active alleles of pTα include one that lacks both the major ectodomain and much of the long cytoplasmic tail (which is unique among antigen receptor chains), and another in which the cytoplasmic tail is substituted with the short tail of TCR Cα. Thus, very little of the pTα chain is required for function. These data support a hypothesis that the primary role of pTα is to stabilize the pre-TCR, and that much of the conserved structure of pTα probably plays a critical regulatory role.
Short-lived and Long-lived Bone Marrow Plasma Cells Are Derived from a Novel Precursor Population
Authors: O'Connor Brian P. , Cascalho Marilia , Noelle Randolph J.
Published: July 2002

The contribution that long-lived bone marrow (BM) plasma cells (PCs) provide to enduring humoral immunity has been underscored by a number of recent studies. However, little is known about the immediate precursors that give rise to long-lived PCs in the BM of immune individuals. We have identified subsets of antigen-experienced B cells within the immune BM that are precursors to PCs. These PC precursors arise in the BM 14 days after immunization and persist for greater than 9 months. Phenotypically distinct subsets of PC precursors give rise to short-lived or long-lived PCs. The differentiation of PC precursors to PCs occurs in the absence of antigen and requires cell division. The functional significance of these newly identified PC precursors in the persistence and quality of the humoral immune response is discussed.
Two Subsets of Naive T Helper Cells with Distinct T Cell Receptor Excision Circle Content in Human Adult Peripheral Blood
Authors: Kimmig Sonja , Przybylski Grzegorz K. , Schmidt Christian A. , Laurisch Katja , Möwes Beate , Radbruch Andreas , Thiel Andreas
Published: July 2002

During ageing thymic function declines and is unable to meet the demand for peripheral T helper (Th) cell replenishment. Therefore, population maintenance of naive Th cells must be at least partly peripherally based. Such peripheral postthymic expansion of recent thymic emigrants (RTEs) during ageing consequently should lead to loss or dilution of T cell receptor excision circles (TRECs) from a subset of naive T cells. We have identified two subsets of naive Th cells in human adult peripheral blood characterized by a striking unequal content of TRECs, indicating different peripheral proliferative histories. TRECs are highly enriched in peripheral naive CD45RA+ Th cells coexpressing CD31 compared with peripheral naive CD45RA+ Th cells lacking CD31 expression, in which TRECs can hardly be detected. Furthermore we show that CD31−CD45RA+ Th cells account for increasing percentages of the naive peripheral Th cell pool during ageing but retain phenotypic and functional features of naive Th cells. As CD31 is lost upon T cell receptor (TCR) engagement in vitro, we hypothesize that TCR triggering is a prerequisite for homeostatically driven peripheral postthymic expansion of human naive RTEs. We describe here the identification of peripherally expanded naive Th cells in human adult blood characterized by the loss of CD31 expression and a highly reduced TREC content.
Constitutive Endocytosis and Degradation of the Pre-T Cell Receptor
Authors: Panigada Maddalena , Porcellini Simona , Barbier Eliane , Hoeflinger Sonja , Cazenave Pierre-André , Gu Hua , Band Hamid , von Boehmer Harald , Grassi Fabio
Published: July 2002

The pre-T cell receptor (TCR) signals constitutively in the absence of putative ligands on thymic stroma and signal transduction correlates with translocation of the pre-TCR into glycolipid-enriched microdomains (rafts) in the plasma membrane. Here, we show that the pre-TCR is constitutively routed to lysosomes after reaching the cell surface. The cell-autonomous down-regulation of the pre-TCR requires activation of the src-like kinase p56lck, actin polymerization, and dynamin. Constitutive signaling and degradation represents a feature of the pre-TCR because the γδTCR expressed in the same cell line does not exhibit these features. This is also evident by the observation that the protein adaptor/ubiquitin ligase c-Cbl is phosphorylated and selectively translocated into rafts in pre-TCR– but not γδTCR-expressing cells. A role of c-Cbl–mediated ubiquitination in pre-TCR degradation is supported by the reduction of degradation through pharmacological inhibition of the proteasome and through a dominant-negative c-Cbl ubiquitin ligase as well as by increased pre-TCR surface expression on immature thymocytes in c-Cbl–deficient mice. The pre-TCR internalization contributes significantly to the low surface level of the receptor on developing T cells, and may in fact be a requirement for optimal pre-TCR function.
Agonist-dependent Phosphorylation of the Inositol 1,4,5-Trisphosphate Receptor
Authors: LeBeau Andrew P. , Yule David I. , Groblewski Guy E. , Sneyd James
Published: July 2002

The properties of inositol 1,4,5-trisphosphate (IP3)-dependent intracellular calcium oscillations in pancreatic acinar cells depend crucially on the agonist used to stimulate them. Acetylcholine or carbachol (CCh) cause high-frequency (10–12-s period) calcium oscillations that are superimposed on a raised baseline, while cholecystokinin (CCK) causes long-period (>100-s period) baseline spiking. We show that physiological concentrations of CCK induce rapid phosphorylation of the IP3 receptor, which is not true of physiological concentrations of CCh. Based on this and other experimental data, we construct a mathematical model of agonist-specific intracellular calcium oscillations in pancreatic acinar cells. Model simulations agree with previous experimental work on the rates of activation and inactivation of the IP3 receptor by calcium (DuFour, J.-F., I.M. Arias, and T.J. Turner. 1997. J. Biol. Chem. 272:2675–2681), and reproduce both short-period, raised baseline oscillations, and long-period baseline spiking. The steady state open probability curve of the model IP3 receptor is an increasing function of calcium concentration, as found for type-III IP3 receptors by Hagar et al. (Hagar, R.E., A.D. Burgstahler, M.H. Nathanson, and B.E. Ehrlich. 1998. Nature. 396:81–84). We use the model to predict the effect of the removal of external calcium, and this prediction is confirmed experimentally. We also predict that, for type-III IP3 receptors, the steady state open probability curve will shift to lower calcium concentrations as the background IP3 concentration increases. We conclude that the differences between CCh- and CCK-induced calcium oscillations in pancreatic acinar cells can be explained by two principal mechanisms: (a) CCK causes more phosphorylation of the IP3 receptor than does CCh, and the phosphorylated receptor cannot pass calcium current; and (b) the rate of calcium ATPase pumping and the rate of calcium influx from the outside the cell are greater in the presence of CCh than in the presence of CCK.
Project ACORN: user reactions
Authors: Kingston Paula , Gadd Elizabeth , Poulter Alan
Published: July 2002

This paper outlines the electronic ‘short loan’ collection of high‐demand journal articles developed by Project ACORN (Access to Course Readings via Networks) (1).

It summarises some preliminary findings on the volume and type of use made of the service, and users' reactions to it. Factors affecting non‐use are also presented. Issues and developments for the future are discussed in the light of experiences to date.
Evolving journal costs: implications for publishers, libraries, and readers
Authors: King Donald W. , Tenopir Carol
Published: July 2002

In this article, we summarize the cost implications of print and electronic publishing for scientific scholarly journal publishers, libraries, and scientists. In each case, we developed detailed cost models to demonstrate the importance of factors that affect publishing and decisions made by libraries and scientists to determine whether to subscribe to a journal; if so, in print or electronic medium, and, if not, what alternative information sources to use. In all instances, estimates of unit cost are essential for understanding the dynamics of the economic and systemic interdependencies of publishers, libraries, and readers.
Almost periodic ultradistributions of Beurling and of Roumieu type
Authors: Gómez-Collado M.
Published: July 2002

We characterize the almost periodic ultradistributions of Beurling and of Roumieu type in terms of classical Bohr almost periodicity. Then we study the Fourier series associated with such an ultradistribution.
On the recursive sequence 𝑥_{𝑛+1}=\frac{𝐴}𝑥_{𝑛}+\frac{1}𝑥_{𝑛-2}
Authors: DeVault R. , Ladas G. , Schultz S.
Published: July 2002

We show that every positive solution of the equation
\[

x

n
+
1

=

A

x

n

+

1

x

n
−
2

,

n
=
0
,
1
,
…
,

x_{n+1} = \frac {A}{x_{n}} + \frac {1}{x_{n-2}}, \hspace {.2in} n = 0, 1, \ldots ,

\]
where

A
∈
(
0
,
∞
)

A \in (0, \infty )

, converges to a period two solution.
Invariant foliations near normally hyperbolic invariant manifolds for semiflows
Authors: Bates Peter , Lu Kening , Zeng Chongchun
Published: July 2002

Let

M
M

be a compact

C
1

C^1

manifold which is invariant and normally hyperbolic with respect to a

C
1

C^1

semiflow in a Banach space. Then in an

ϵ
\epsilon

-neighborhood of

M
M

there exist local

C
1

C^1

center-stable and center-unstable manifolds

W

c
s

(
ϵ
)

W^{cs}(\epsilon )

and

W

c
u

(
ϵ
)

W^{cu}(\epsilon )

, respectively. Here we show that

W

c
s

(
ϵ
)

W^{cs}(\epsilon )

and

W

c
u

(
ϵ
)

W^{cu}(\epsilon )

may each be decomposed into the disjoint union of

C
1

C^1

submanifolds (leaves) in such a way that the semiflow takes leaves into leaves of the same collection. Furthermore, each leaf intersects

M
M

in a single point which determines the asymptotic behavior of all points of that leaf in either forward or backward time.
On Bessel distributions for quasi-split groups
Authors: Baruch Ehud
Published: July 2002

We show that the Bessel distribution attached by Gelfand and Kazhdan and by Shalika to a generic representation of a quasi-split reductive group over a local field is given by a function when it is restricted to the open Bruhat cell. As in the case of the character distribution, this function is real analytic for archimedean fields and locally constant for non-archimidean fields.
Defect zero blocks for finite simple groups
Authors: Granville Andrew , Ono Ken
Published: July 2002

We classify those finite simple groups whose Brauer graph (or decomposition matrix) has a

p
p

-block with defect 0, completing an investigation of many authors. The only finite simple groups whose defect zero

p
−

p-

blocks remained unclassified were the alternating groups

A

n

A_{n}

. Here we show that these all have a

p
p

-block with defect 0 for every prime

p
≥
5

p\geq 5

. This follows from proving the same result for every symmetric group

S

n

S_{n}

, which in turn follows as a consequence of the

t
t

-core partition conjecture, that every non-negative integer possesses at least one

t
t

-core partition, for any

t
≥
4

t\geq 4

. For

t
≥
17

t\geq 17

, we reduce this problem to Lagrange’s Theorem that every non-negative integer can be written as the sum of four squares. The only case with

t
>
17

t>17

, that was not covered in previous work, was the case

t
=
13

t=13

. This we prove with a very different argument, by interpreting the generating function for

t
t

-core partitions in terms of modular forms, and then controlling the size of the coefficients using Deligne’s Theorem (née the Weil Conjectures). We also consider congruences for the number of

p
p

-blocks of

S

n

S_{n}

, proving a conjecture of Garvan, that establishes certain multiplicative congruences when

5
≤
p
≤
23

5\leq p \leq 23

. By using a result of Serre concerning the divisibility of coefficients of modular forms, we show that for any given prime

p
p

and positive integer

m
m

, the number of

p
−

p-

blocks with defect 0 in

S
n

S_n

is a multiple of

m
m

for almost all

n
n

. We also establish that any given prime

p
p

divides the number of

p
−

p-

modularly irreducible representations of

S

n

S_{n}

, for almost all

n
n

.
Entire solutions of semilinear elliptic equations in ℝ³ and a conjecture of De Giorgi
Authors: Ambrosio Luigi , Cabré Xavier
Published: July 2002

In 1978 De Giorgi formulated the following conjecture. Let

u
u

be a solution of

Δ
u
=

u

3

−
u

\Delta u=u^{3}-u

in all of

R

n

\mathbb {R}^{n}

such that

|
u
|
≤
1

\vert u\vert \le 1

and

∂

n

u
>
0

\partial _{n} u >0

in

R

n

\mathbb {R}^{n}

. Is it true that all level sets

{
u
=
λ
}

\{ u=\lambda \}

of

u
u

are hyperplanes, at least if

n
≤
8

n\le 8\,

? Equivalently, does

u
u

depend only on one variable? When

n
=
2

n=2

, this conjecture was proved in 1997 by N. Ghoussoub and C. Gui. In the present paper we prove it for

n
=
3

n=3

. The question, however, remains open for

n
≥
4

n\ge 4

. The results for

n
=
2

n=2

and 3 apply also to the equation

Δ
u
=

F
′

(
u
)

\Delta u=F’(u)

for a large class of nonlinearities 

F
F

.
Discrepancy in arithmetic progressions
Authors: Matoušek Jiří , Spencer Joel
Published: July 2002

It is proven that there is a two-coloring of the first

n
n

integers for which all arithmetic progressions have discrepancy less than

c
o
n
s
t

.

n

1

/

4

\mathrm {const}.n^{1/4}

. This shows that a 1964 result of K. F. Roth is, up to constants, best possible.
CSN1 N-Terminal–dependent Activity Is Required for Arabidopsis Development But Not for Rub1/Nedd8 Deconjugation of Cullins: A Structure-Function Study of CSN1 Subunit of COP9 Signalosome
Authors: Wang Xiping , Kang Dingming , Feng Suhua , Serino Giovanna , Schwechheimer Claus , Wei Ning
Published: July 2002

The COP9 signalosome (CSN) is a multifunctional protein complex essential for arabidopsis development. One of its functions is to promote Rub1/Nedd8 deconjugation from the cullin subunit of the Skp1-cullin-F-box ubiquitin ligase. Little is known about the specific role of its eight subunits in deneddylation or any of the physiological functions of CSN. In the absence of CSN1 (thefus6 mutant), arabidopsis CSN complex cannot assemble, which destabilizes multiple CSN subunits and contributes, together with the loss of CSN1, to the phenotype of fus6. To distinguish CSN1-specific functions, we attempted to rescue the complex formation with deletion or point-mutation forms of CSN1 expressed as transgenes in fus6. We show that the central domain of CSN1 is critical for complex assembly, whereas the C-terminal domain has a supporting role. By expressing the C231 fragment, which contains the structural information but lacks the presumed functional domain located at the N terminus, we have rescued the complex formation and restored the Rub1/Nedd8 deconjugation activity on cullins (fus6/C231). Nonetheless, fus6/C231exhibits pleiotropic phenotype, including photomorphogenic defects and growth arrest at seedling stage. We conclude that CSN1 N-terminal domain is not required for the Rub1/Nedd8 deconjugation activity of cullins, but contributes to a significant aspect of CSN functions that are essential for plant development.
Hypoxia-inducible Factor-1α mRNA Contains an Internal Ribosome Entry Site That Allows Efficient Translation during Normoxia and Hypoxia
Authors: Lang Kenneth J. D. , Kappel Andreas , Goodall Gregory J.
Published: July 2002

HIF-1α is the regulated subunit of the HIF-1 transcription factor, which induces transcription of a number of genes involved in the cellular response to hypoxia. The HIF-1α protein is rapidly degraded in cells supplied with adequate oxygen but is stabilized in hypoxic cells. Using polysome profile analysis, we found that translation of HIF-1α mRNA in NIH3T3 cells is spared the general reduction in translation rate that occurs during hypoxia. To assess whether the 5′UTR of the HIF-1α mRNA contains an internal ribosome entry site (IRES), we constructed a dicistronic reporter with the HIF-1α 5′UTR inserted between two reporter coding regions. We found that the HIF-1α 5′UTR promoted translation of the downstream reporter, indicating the presence of an IRES. The IRES had activity comparable to that of the well-characterized c-myc IRES. IRES activity was not affected by hypoxic conditions that caused a reduction in cap-dependent translation, and IRES activity was less affected by serum-starvation than was cap-dependent translation. These data indicate that the presence of an IRES in the HIF-1α 5′UTR allows translation to be maintained under conditions that are inhibitory to cap-dependent translation.
Spectrum: spectral analysis of phylogenetic data.
Authors: Charleston M A
Published: July 2002

MOTIVATION: Spectrum is a new Macintosh and Microsoft Windows program designed to read in phylogenetic four-state or binary data in NEXUS format, and output the corresponding bipartition spectra. It can be used to find the tree whose expected spectrum is closest to the observed spectrum (the closest tree, Hendy, Discr, Math., 96, 51-58,. 1991).
Prediction of MHC class II-binding peptides using an evolutionary algorithm and artificial neural network.
Authors: Brusic V , Rudy G , Honeyman G , Hammer J , Harrison L
Published: July 2002

MOTIVATION: Prediction methods for identifying binding peptides could minimize the number of peptides required to be synthesized and assayed, and thereby facilitate the identification of potential T-cell epitopes. We developed a bioinformatic method for the prediction of peptide binding to MHC class II molecules. RESULTS: Experimental binding data and expert knowledge of anchor positions and binding motifs were combined with an evolutionary algorithm (EA) and an artificial neural network (ANN): binding data extraction --> peptide alignment --> ANN training and classification . This method, termed PERUN, was implemented for the prediction of peptides that bind to HLA-DR4(B1*0401). The respective positive predictive values of PERUN predictions of high-, moderate-, low- and zero-affinity binders were assessed as 0.8, 0.7, 0.5 and 0.8 by cross-validation, and 1.0, 0.8, 0.3 and 0.7 by experimental binding. This illustrates the synergy between experimentation and computer modeling, and its application to the identification of potential immunotherapeutic peptides. AVAILABILITY: Software and data are available from the authors upon request. CONTACT: vladimir@wehi.edu. au
Bioinorganic motifs: towards functional classification of metalloproteins
Authors: Degtyarenko Kirill
Published: July 2002

The habitat of bioinorganic motifs (BIMs) is at the interface of biological inorganic chemistry and bioinformatics. BIM is defined as a common structural feature shared by functionally related, but not necessarily homologous, proteins, and consisting of the metal atom(s) and first coordination shell ligands. BIMs appear to be suitable for classification of metal centres at any level, from groups of unrelated proteins with similar function to different functional states of the same protein, and for description of possible evolutionary relationships of metalloproteins. However, they have not attracted wide attention from the bioinformatics community. Although their presence is appreciated, they are difficult to predict—therefore the current ‘high-throughput’ initiatives are likely to miss or ignore them altogether. The protein sequence databases do not distinguish between proteins containing different prosthetic groups (unless they have different sequences) or between apo- and holoprotein. On the other hand, the protein structure databases include data on ‘hetero compounds’ of various origin but these data are often inconsistent. A number of specialized databases dealing with BIMs and attempts to classify them are reviewed. Supplementary information: The additional bibliography and list of Internet resources on bioinorganic chemistry are available at http://www.ebi.ac.uk/~kirill/biometal/