|
| ||
|
|
||
Cell Development (cell + development)
Kinds of Cell Development Selected AbstractsZebrafish mutants with disrupted early T-cell and thymus development identified in early pressure screenDEVELOPMENTAL DYNAMICS, Issue 9 2008Nikolaus S. Trede Abstract Generation of mature T lymphocytes requires an intact hematopoietic stem cell compartment and functional thymic epithelium. We used the zebrafish (Danio rerio) to isolate mutations that affect the earliest steps in T lymphopoiesis and thymic organogenesis. Here we describe the results of a genetic screen in which gynogenetic diploid offspring from heterozygous females were analyzed by whole-mount in situ hybridization for the expression of rag-1. To assess immediately if a global defect in hematopoiesis resulted in the mutant phenotype, ,-embryonic globin expression was simultaneously assayed for multilineage defects. In this report, we present the results obtained with this strategy and show representative mutant phenotypes affecting early steps in T-cell development and/or thymic epithelial cell development. We discuss the advantage of this strategy and the general usefulness of the zebrafish as a model system for vertebrate lymphopoiesis and thymic organogenesis. Developmental Dynamics 237:2575,2584, 2008. © 2008 Wiley-Liss, Inc. [source] Genes involved in the RNA interference pathway are differentially expressed during sea urchin developmentDEVELOPMENTAL DYNAMICS, Issue 11 2007Jia L. Song Abstract RNA-mediated interference (RNAi) is a conserved gene silencing mechanism that involves double-stranded RNA as a signal to trigger the sequence-specific degradation of target mRNA, resulting in posttranscriptional silencing and/or translational repression. Bioinformatic searches in the sea urchin genome database identified homologs of Drosha, DGCR5, Dicer, TRBP, Exportin-5, and Argonautes. Quantitative, real-time polymerase chain reaction indicated that all mRNA accumulate in eggs and in variable levels throughout early development. Whole-mount in situ RNA hybridization showed that all of the important players of the RNAi silencing pathway have abundant mRNA accumulation in oocytes and eggs, but have distinct spatial and temporal expression patterns throughout development. Sequence analysis revealed that each of the four Argonautes examined contain conserved residues important for RNAseH activity within the Piwi domain. This study elucidated that genes involved in the RNAi silencing pathway have dynamic expression and, thus, may have regulatory roles during germ cell development and embryogenesis. Developmental Dynamics 236:3180,3190, 2007. © 2007 Wiley-Liss, Inc. [source] GATA-4 is required for sex steroidogenic cell development in the fetal mouseDEVELOPMENTAL DYNAMICS, Issue 1 2007Malgorzata Bielinska Abstract The transcription factor GATA-4 is expressed in Sertoli cells, steroidogenic Leydig cells, and other testicular somatic cells. Previous studies have established that interaction between GATA-4 and its cofactor FOG-2 is necessary for proper Sry expression and all subsequent steps in testicular organogenesis, including testis cord formation and differentiation of both Sertoli and fetal Leydig cells. Since fetal Leydig cell differentiation depends on Sertoli cell,derived factors, it has remained unclear whether GATA-4 has a cell autonomous role in Leydig cell development. We used two experimental systems to explore the role of GATA-4 in the ontogeny of testicular steroidogenic cells. First, chimeric mice were generated by injection of Gata4,/, ES cells into Rosa26 blastocysts. Analysis of the resultant chimeras showed that in developing testis Gata4,/, cells can contribute to fetal germ cells and interstitial fibroblasts but not fetal Leydig cells. Second, wild-type or Gata4,/, ES cells were injected into the flanks of intact or gonadectomized nude mice and the resultant teratomas examined for expression of steroidogenic markers. Wild-type but not Gata4,/, ES cells were capable of differentiating into gonadal-type steroidogenic lineages in teratomas grown in gonadectomized mice. In chimeric teratomas derived from mixtures of GFP-tagged Gata4+/+ ES cells and unlabeled Gata4,/, ES cells, sex steroidogenic cell differentiation was restricted to GFP-expressing cells. Collectively these data suggest that GATA-4 plays an integral role in the development of testicular steroidogenic cells. Developmental Dynamics 236:203,213, 2007. © 2006 Wiley-Liss, Inc. [source] The zebrafish bHLH PAS transcriptional regulator, single-minded 1 (sim1), is required for isotocin cell developmentDEVELOPMENTAL DYNAMICS, Issue 8 2006Jennifer L. Eaton Abstract A wide range of physiological and behavioral processes, such as social, sexual, and maternal behaviors, learning and memory, and osmotic homeostasis are influenced by the neurohypophysial peptides oxytocin and vasopressin. Disruptions of these hormone systems have been linked to several neurobehavioral disorders, including autism, Prader-Willi syndrome, affective disorders, and obsessive-compulsive disorder. Studies in zebrafish promise to reveal the complex network of regulatory genes and signaling pathways that direct the development of oxytocin- and vasopressin-like neurons, and provide insight into factors involved in brain disorders associated with disruption of these systems. Isotocin, which is homologous to oxytocin, is expressed early, in a simple pattern in the developing zebrafish brain. Single-minded 1 (sim1), a member of the bHLH-PAS family of transcriptional regulatory genes, is required for terminal differentiation of mammalian oxytocin cells and is a master regulator of neurogenesis in Drosophila. Here we show that sim1 is expressed in the zebrafish forebrain and is required for isotocin cell development. The expression pattern of sim1 mRNA in the embryonic forebrain is dynamic and complex, and overlaps with isotocin expression in the preoptic area. We provide evidence that the role of sim1 in zebrafish neuroendocrine cell development is evolutionarily conserved with that of mammals. Developmental Dynamics 235:2071,2082, 2006. © 2006 Wiley-Liss, Inc. [source] Neurotrophin-3 signaling in mammalian Merkel cell developmentDEVELOPMENTAL DYNAMICS, Issue 4 2003Viktor Szeder Abstract Merkel cells are sensory cells of neural crest origin. Because little is known about the mechanisms that direct their differentiation, we have investigated the potential role of a candidate regulatory factor, neurotrophin-3 (NT-3). At embryonic day 16.5 (E 16.5), neither NT-3 nor its primary receptors, TrkC and p75NTR are expressed by Merkel cells in the murine whisker. At the time of birth, however, Merkel cells are immunoreactive for NT-3, TrkC and p75NTR. In TrkC null and NT-3 null mice, Merkel cells differentiate initially, but undergo apoptosis perinatally. These results show that NT-3 signaling is not required for the differentiation of Merkel cells, but that it is essential for their postnatal survival. Developmental Dynamics 228:623,629, 2003. © 2003 Wiley-Liss, Inc. [source] Age-dependent differential expression of genes involved in steroid signalling pathway in the brain of protandrous black porgy, Acanthopagrus schlegeliDEVELOPMENTAL NEUROBIOLOGY, Issue 5 2009Sherly Tomy Abstract The mechanisms underlying brain sex differentiation in animals are poorly understood. In the present study, using black porgy, Acanthopagrus schlegeli, as primary experimental model, we investigated the temporal expression patterns of receptors for androgen (ar) and estrogen (esr1 and esr2a) in the brain during posthatching ages and analyzed them against the timing of gonadal germ cell development. We hypothesized that endogenous estrogens naturally masculinize the brain of black porgy. The expression of sex steroid receptors was studied in relation to a wider suite of other related genes (nr5a2, nr0b1, star, and cyp19a1b) to provide some insight into the monomale sex differentiation pattern observed in this species. Our results revealed a highly significant increase in esr1 together with the increase in esr2a at 120 dph (days posthatching), suggesting a significant role for esr in sex differentiation in this species. Temporal expression patterns of nr5a2, nr0b1, star, sex steroid receptors, and cyp19a1b in the brain provided evidence for their physiological roles in the monomale sex differentiation in this species. The expression of nr5a2, star, ar, esr1, esr2a, and cyp19a1b increased at 120 dph, a period when brain sex differentiation probably occurs in this species. The study also suggests that neurosteroidogenesis in black porgy may be regulated by both nr5a2 -dependent and nr5a2 -independent mechanisms. The results demonstrated striking differences in the abundance of the gene transcripts in discrete brain region throughout ontogeny. In addition, the sex steroid hormone levels and aromatase activity in brain at different developmental states and the changes in the gene expression patterns in response to aromatase inhibitor treatment are also discussed. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] ,-cell development: the role of intercellular signalsDIABETES OBESITY & METABOLISM, Issue 2008R. Scharfmann Understanding in detail how pancreatic endocrine cells develop is important for many reasons. From a scientific point of view, elucidation of such a complex process is a major challenge. From a more applied point of view, this may help us to better understand and treat specific forms of diabetes. Although a variety of therapeutic approaches are well validated, no cure for diabetes is available. Many arguments indicate that the development of new strategies to cure diabetic patients will require precise understanding of the way ,-cells form during development. This is obvious for a future cell therapy using ,-cells produced from embryonic stem cells. This also holds true for therapeutic approaches based on regenerative medicine. In this review, we summarize our current knowledge concerning pancreatic development and focus on the role of extracellular signals implicated in ,-cell development from pancreatic progenitors. [source] The role of pdx1 and HNF6 in proliferation and differentiation of endocrine precursorsDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 2 2004Laura Wilding Abstract Ex vivo expansion of embryonic stem cells (ES cells) or pancreatic stem cells for insulin delivery to diabetic patients provides potential for the restoration of islet function in these individuals. Understanding the spatial and temporal requirements of crucial factors for endocrine progenitor specification, proliferation, and terminal differentiation remains a major challenge in the field of pancreas development. Here, we provide speculation as to the role of pdx1 and HNF6 in these different stages of pancreatic endocrine cell development. At the time when islets begin to form within the pancreas, the expression patterns of pdx1 and HNF6 diverge, suggesting distinct functions for each of the genes over the course of endocrine cell development. The current body of evidence provides support for a role of both factors in early endocrine specification as well as a requirement for pdx1 in the generation of mature pancreatic endocrine cells. The precise temporal requirement of HNF6 in the production of terminally differentiated endocrine cells remains unclear. Future studies in this area will rely on conditionally manipulatable systems in combination with lineage-tracing studies for a more accurate assessment of pdx1 and HNF6 function at different stages along the pathway of endocrine cell development. Copyright © 2004 John Wiley & Sons, Ltd. [source] Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revisionACTA ZOOLOGICA, Issue 4 2010Arkadiy A. Reunov Abstract Reunov, A.A., Yurchenko, O.V., Alexandrova, Y.N. and Radashevsky, V.I. 2009. Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revision. ,Acta Zoologica (Stockholm) 91: 477,456. To characterize novel features that will be useful in the discussion and validation of the spionid polychaete Boccardiella hamata from the Sea of Japan, the successive stages of spermatogenesis were described and illustrated. Spermatogonia, spermatocytes and early spermatids are aflagellar cells that develop synchronously in clusters united by a cytophore. At the middle spermatid stage, the clusters undergo disintegration and spermatids produce flagella and float separately in coelomic fluid as they transform into sperm. Spermatozoa are filiform. The ring-shaped storage platelets are located along the anterior nuclear area. The nucleus is cupped by a conical acrosome. A nuclear plate is present between the acrosome and nucleus. The nucleus is a cylinder with the implantation fossa throughout its length and with the anterior part of the flagellum inside the fossa. There is only one centriole, serving as a basal body of the flagellum, situated in close vicinity of the acrosomal area. A collar of four mitochondria is located under the nuclear base. The ultrastructure of B. hamata spermatozoa from the Sea of Japan appears to be close to that of B. hamata from Florida described by Rice (Microscopic Anatomy of Invertebrates, Wiley-Liss, Inc., New York, 1992), suggesting species identity of the samples from the two regions. However, more detailed study of Florida's B. hamata sperm is required for a reliable conclusion concerning the similarity of these two polychaetes. In addition to sperm structure, features such as the cytophore-assigned pattern of spermatogenic cell development, the synchronous pattern of cell divisions, the non-flagellate early spermatogenic stages, and the vesicle amalgamation that drives meiotic cell cytokinesis and spermatid diorthosis will likely be useful in future testing of the validity of B. hamata and sibling species throughout the world. [source] Development and maturation of invariant NKT cells in the presence of lysosomal engulfmentEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2009Tiziana Plati Abstract A defect in invariant NKT (iNKT) cell selection was hypothesized in lysosomal storage disorders (LSD). Accumulation of glycosphingolipids (GSL) in LSD could influence lipid loading and/or presentation causing entrapment of endogenous ligand(s) within storage bodies or competition of the selecting ligand(s) by stored lipids for CD1d binding. However, when we analyzed the iNKT cell compartment in newly tested LSD animal models that accumulate GSL, glycoaminoglycans or both, we observed a defective iNKT cell selection only in animals affected by multiple sulfatase deficiency, in which a generalized aberrant T-cell development, rather than a pure iNKT defect, was present. Mice with single lysosomal enzyme deficiencies had normal iNKT cell development. Thus, GSL/glycoaminoglycans storage and lysosomal engulfment are not sufficient for affecting iNKT cell development. Rather, lipid ligand(s) or storage compounds, which are affected in those LSD lacking mature iNKT cells, might indeed be relevant for iNKT cell selection. [source] Redundant role for Zap70 in B cell development and activationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2008Farnaz Fallah-Arani Dr. Abstract Expression of the Syk family tyrosine kinase Zap70 is strongly correlated with poor clinical outcome in chronic lymphocytic leukemia, the most common human leukemia characterized by B cell accumulation. The expression of Zap70 may reflect the specific cell of origin of the tumor or may contribute to pathology. Thus, the normal role of Zap70 in B cell physiology is of great interest. While initial studies reported that Zap70 expression in the mouse was limited to T and NK cells, more recent work has shown expression in early B cell progenitors and in splenic B cells, suggesting that the kinase may play a role in the development or activation of B cells. In this study, we show that Zap70 is expressed in all developing subsets of B cells as well as in recirculating B cells, marginal zone B cells and peritoneal B1 cells. Analysis of Zap70-deficient mice shows no unique role for Zap70 in either the development of B cells or in their in vitro and in vivo activation. However, we show that Zap70 can rescue the defective positive selection of immature B cells into the recirculating pool in Syk-deficient mice, demonstrating functional redundancy between these two kinases. [source] Recombinase-deficient T cell development by selective accumulation of CD3 into lipid raftsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2008Denise Ferrera Abstract The pre-T cell receptor (pre-TCR) promotes the development of thymocytes with productive rearrangement at the TCR ,,chain locus by signaling in a ligand-independent fashion. The TCR ,,chain associates with the invariant pre-T, (pT,) chain, which bears specific charged residues in the extracellular portion mediating pre-TCR self-oligomerization. In recombinase-deficient thymocytes, calnexin (CNX) associated with CD3 chains is inefficiently retained in the endoplasmic reticulum (ER) and weakly expressed in the plasma membrane. Deliberate cross-linking of CNX/CD3 complexes mimics pre-TCR signaling. Here, we show that, analogously to the pT, chain, surface CNX is palmitoylated and that CD3 prominently accumulated in lipid rafts upon cross-linking. Mutant CNX isoforms devoid of ER retention determined pre-TCR-like signaling and simulated ,,selection only when stably translocating CD3 to lipid rafts. Inclusion of the palmitoylated cytoplasmic tail from the pT, chain in recombinant CNX strikingly improved the pre-TCR-like signaling efficiency of CNX/CD3 in rafts. This study indicates that lipid rafts in the plasma membrane represent proficient microdomains for the initiation of pre-TCR signaling, and supports the view that ,,selection by oligomerized pre-TCR is implemented by the pT, cytoplasmic tail. [source] From gene amplification to V(D)J recombination and back: A personal account of my early years in B cell biologyEUROPEAN JOURNAL OF IMMUNOLOGY, Issue S1 2007Frederick Abstract I have been invited to write a short historical feature in the context of being a co-recipient with Klaus Rajewsky and Fritz Melchers of the 2007,Novartis Prize in Basic Immunology that was given in the general area of the molecular biology of B cells. In this feature, I cover the main points of the short talk that I presented at the Award Ceremony at the International Immunology Congress in Rio de Janeiro, Brazil. This talk focused primarily on the work and people involved early on in generating the models and ideas that have formed the basis for my ongoing efforts in the areas of V(D)J recombination and B cell development. [source] IL-35 is a novel cytokine with therapeutic effects against collagen-induced arthritis through the expansion of regulatory T cells and suppression of Th17 cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2007Wanda Niedbala Abstract Epstein-Barr virus-induced gene,3 (EBI3) and the p35 subunit of IL-12 have been reported to form a heterodimeric hematopoietin in human and mouse. We have constructed a heterodimeric protein covalently linking EBI3 and p35, to form a novel cytokine which we now call IL-35. The Fc fusion protein of IL-35 induced proliferation of murine CD4+CD25+ and CD4+CD25, T cells when stimulated with immobilized anti-CD3 and anti-CD28 antibodies in vitro. The IL-35-expanded CD4+CD25+ T cell population expressed Foxp3 and produced elevated levels of IL-10, whereas the IL-35-induced CD4+CD25, T cells produced IFN-, but not IL-4. The in vitro expanded CD4+CD25+ T cells retained their suppressive functions against CD4+CD25, effector cells. Furthermore, when cultured with soluble anti-CD3 antibody and antigen-presenting cells, IL-35 suppressed the proliferation of CD4+CD25, effector cells. Moreover, IL-35 inhibited the differentiation of Th17 cells in vitro. In vivo, IL-35 effectively attenuated established collagen-induced arthritis in mice, with concomitant suppression of IL-17 production but enhanced IFN-, synthesis. Thus, IL-35 is a novel anti-inflammatory cytokine suppressing the immune response through the expansion of regulatory T cells and suppression of Th17 cell development. [source] Deletion of the LIME adaptor protein minimally affects T and B cell development and functionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2007Claude Grégoire Abstract LIME (Lck-interacting membrane protein) is a transmembrane adaptor that associates with the Lck and Fyn protein tyrosine kinases and with the C-terminal Src kinase (Csk). To delineate the role of LIME in vivo, LIME-deficient mice were generated. Although Lime transcripts were expressed in immature and mature B and T cells, the absence of LIME impeded neither the development nor the function of B and T cells. TCR transgenic mice deprived of LIME showed, however, a 1.8-fold enhancement in positive selection. Since B cells and activated T cells express LIME and the related adaptor NTAL, mice lacking both adaptors were generated. Double-deficient mice showed no defect in the development and function of B and T cells, and the lack of LIME had no effect on the autoimmune syndrome that develops in aged NTAL-deficient mice. In contrast to a previous report, we further showed that this autoimmune syndrome develops in the absence of T cells. Therefore, our in vivo results refute all the previous roles postulated for LIME on the basis of studies of transformed B and T cells and demonstrate that LIME has no seminal role in the signaling cassette operated by antigen receptors and coreceptors. [source] In vivo disruption of T cell development by expression of a dominant-negative polypeptide designed to abolish the SLP-76/Gads interactionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2007Martha Abstract Multi-molecular complexes nucleated by adaptor proteins play a central role in signal transduction. In T cells, one central axis consists of the assembly of several signaling proteins linked together by the adaptors linker of activated T cells (LAT), Src homology,2 domain-containing leukocyte-specific phosphoprotein of 76,kDa (SLP-76), and Grb2-related adaptor downstream of Shc (Gads). Each of these adaptors has been shown to be important for normal T cell development, and their proper sub-cellular localization is critical for optimal function in cell lines. We previously demonstrated in Jurkat T cells and a rat basophilic leukemic cell line that expression of a 50-amino acid polypeptide identical to the site on SLP-76 that binds to Gads blocks proper localization of SLP-76 and SLP-76-dependent signaling events. Here we extend these studies to investigate the ability of this polypeptide to inhibit TCR-induced integrin activity in Jurkat cells and to inhibit in vivo thymocyte development and primary T cell function. These data provide evidence for the in vivo function of a dominant-negative peptide based upon the biology of SLP-76 action and suggest the possibility of therapeutic potential of targeting the SLP-76/Gads interaction. [source] Redefining epithelial progenitor potential in the developing thymusEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2007Simona Abstract Cortical and medullary epithelium represent specialised cell types that play key roles in thymocyte development, including positive and negative selection of the T cell repertoire. While recent evidence shows that these epithelial lineages share a common embryonic origin, the phenotype and possible persistence of such progenitor cells in the thymus at later stages of development remain controversial. Through use of a panel of reagents including the putative progenitor marker Mts24, we set out to redefine the stages in the development of thymic epithelium. In the early embryonic day (E)12 thymus anlagen we find that almost all epithelial cells are uniformly positive for Mts24 expression. In addition, while the thymus at later stages of development was found to contain distinct Mts24+ and Mts24, epithelial subsets, thymus grafting experiments show that both Mts24+ and Mts24, epithelial subsets share the ability to form organised cortical and medullary thymic microenvironments that support T cell development, a function shown previously to be lost in the Mts24, cells by E15 when lower cell doses were used. Our data help to clarify stages in thymic epithelial development and provide important information in relation to currently used markers of epithelial progenitors. See accompanying commentary: http://dx.doi.org/10.1002/eji.200737709 [source] Germ-line and rearranged Tcrd transcription distinguish bona fide NK cells and NK-like ,,,T cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2007Charles Abstract NK cells and ,,,T cells are distinct subsets of lymphocytes that contextually share multiple phenotypic and functional characteristics. However, the acquisition and the extent of these similarities remain poorly understood. Here, using T cell receptor ,,locus-histone,2B-enhanced GFP (Tcrd-H2BEGFP) reporter mice, we show that germ-line transcription of Tcrd occurs in all maturing NK cells. We also describe a population of mouse NK-like cells that are indistinguishable from "bona fide" NK cells using standard protocols. Requirements for V(D)J recombination and a functional thymus, along with very low-level expression of surface TCR,, but high intracellular CD3, define these cells as ,,,T cells. "NK-like ,,,T cells" are CD127+, have a memory-activated phenotype, express multiple NK cell receptors and readily produce interferon-, in response to IL-12/IL-18 stimulation. The close phenotypic resemblance between NK cells and NK-like ,,,T cells is a source of experimental ambiguity in studies bridging NK and T cell biology, such as those on thymic NK cell development. Instead, it ascribes chronic TCR,, engagement as a means of acquiring NK-like function. See accompanying commentary: at http://dx.doi.org/10.1002/eji.200737418 [source] Expression of a non-DNA-binding Ikaros isoform exclusively in B cells leads to autoimmunity but not leukemogenesisEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2007Heather Wojcik Abstract Ikaros is a transcriptional regulator whose function is essential for B cell development. It is expressed in the hematopoietic stem cell (HSC) through the mature B cell stage. Using genetically engineered mice in which the endogenous Ikaros gene is disrupted, it has been shown that a lack of Ikaros leads to a block in B cell development and that its severe diminution results in a hyperresponsive B cell compartment. Ikaros expression within the HSC has led to speculation as to whether the role of Ikaros in B cell biology is largely accomplished prior to B cell specification. In addition, widespread expression of Ikaros in hematopoietic cells leads to the possibility that some or all of the observed defects are not B cell autonomous. In this report, we demonstrate that over-expression of a dominant interfering Ikaros isoform exclusively in B cells has profound effects on mature B cell function. We provide evidence that continued high-level expression of Ikaros is essential for homeostasis of peripheral lymphocytes and maintenance of B cell tolerance. We also show that deregulation of Ikaros activity does not rapidly result in B cell leukemogenesis as it does with 100% penetrance within the T cell lineage. [source] Btk and phospholipase,C,2 can function independently during B cell developmentEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2007Kristina Abstract The pre-BCR and the BCR regulate B cell development via a signalosome nucleated by the adaptor protein B cell linker protein (BLNK). Formation of this complex facilitates activation of phospholipase,C (PLC),,2 by Bruton's tyrosine kinase (Btk). To determine whether Btk and PLC,2 also have separate functions, we generated Btk,/,PLC,2,/, mice. They demonstrated a block in development at the pre-B,stage and increased pre-BCR surface expression. This phenotype was more severe than that of Btk,/, or PLC,2,/, mice. Although both Btk and PLC,2 were required for proliferation of splenic B cells in response to BCR cross-linking, they contributed differently to anti-IgM-induced phosphorylation of ERK. Btk,/, and PLC,2,/, mice each had a reduced frequency of Ig,-expressing B cells and impaired migration of pre-B cells towards stromal cell-derived factor,1. However, the increase in pre-B cell malignancy that occurs in BLNK,/, mice in the absence of Btk was not observed in the absence of PLC,2. Thus, Btk and PLC,2 act both in concert and independently throughout B cell development. [source] To switch or not to switch , the opposing roles of TACI in terminal B cell differentiationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2007Ulrich Salzer MD Abstract The TNF superfamily ligands BAFF and APRIL and their three receptors BAFFR, BCMA, and TACI comprise a network that is critically involved in the development and function of humoral immunity. Failure of this complex system is associated with autoimmune disease, B lymphocyte tumours, and antibody deficiency. While BAFF:BAFFR interactions control peripheral B cell survival and homeostasis, BCMA function seems limited to the survival of long-lived bone marrow plasma cells. The functional activity of the third receptor TACI is, however, ambiguous: while TACI,/, mice predominantly develop autoimmunity and lymphoproliferation, TACI deficiency in humans primarily manifests itself as an antibody deficiency syndrome. An article in this issue of the European Journal of Immunology demonstrates a negative regulation via TACI in human B cells by using TACI specific antibodies. B cell proliferation, class switch recombination, and Ig production induced by various stimuli were inhibited via TACI. Within the BAFF/APRIL network, the expression of the receptors and ligands is spatially, as well as temporally, highly regulated at various stages of B cell development and function. Defining the exact contribution of TACI stimulation by specific triggers in vitro enables us to better understand the complex, context-dependent responses initiated by TACI in vivo. See accompanying article http://dx.doi.org/10.1002/eji.200636623 [source] The key regulators of adult T helper cell responses, STAT6 and T-bet, are established in early life in miceEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2006Shawn Rose Abstract Murine neonatal immunity is typically Th2 biased. This is characterized by high-level IL-4 production at all phases of the immune response and poor IFN-, memory responses. The differential expression of Th1/Th2 cytokines by neonates and adults could arise if the critical regulators of Th differentiation and function, STAT6 and T-bet, operate differently during the neonatal period. To test this idea, the Th cell responses of wild-type, T-bet-deficient, or STAT6-deficient mice were compared in vitro and in vivo. The absence of these factors had similar qualitative effects on the development of effector function in neonates and adults, i.e., if a Th lineage was inhibited or enhanced in adult animals, a similar phenomenon was observed in neonates. However, there was a striking difference observed in the in vivo Th1 memory responses of STAT6-deficient mice initially immunized as neonates. Antigen-specific IFN-, production was increased 50,100-fold in STAT6-deficient neonates, achieving levels similar to those of STAT6-deficient adults. These findings demonstrate that STAT6 and T-bet signals are central in shaping Th responses in wild-type neonates, as in adult mice, and that the master regulators of Th cell development and function are already firmly established in early life. [source] Complex regulation of CCR9 at multiple discrete stages of T,cell developmentEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2006Marc-André Wurbel Dr. Abstract We have conducted a comprehensive assessment of CCR9 expression and function at the important milestone stages of murine thymocyte development. We reveal an unusually complex regulatory pattern, in which CCR9 influences T,cell development at several widely dispersed stages. We find that CCR9 is not expressed within the thymus until the double-negative (DN)3 stage, although it appears to contribute to T,cell precursor development prior to residence in the thymus. CCR9 expression is influenced by pre-T,cell receptor signals, and is dramatically up-regulated in a population that appears to be transitional between the DN4 and double-positive stages. In the periphery, functional CCR9 is expressed by all naive CD8 T,cells, but not by naive CD4 T,cells. To our knowledge, this latter finding is the first difference observed in homing receptor expression between naive lymphocyte populations. This suggests that naive CD8 T,cells might have access to lymphoid microenvironments from which naive CD4 T,cells are excluded. [source] Glucocorticoid-induced TNFR family-related protein (GITR) activation exacerbates murine asthma and collagen-induced arthritisEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2005Manish Patel Abstract Glucocorticoid-induced TNFR family-related protein (GITR) is expressed at low levels on resting T cells, B cells and macrophages but at high levels on regulatory T cells (Treg). Although GITR expression is up-regulated on CD4+ effector cells upon activation, the role of GITR in Th1 and Th2 cell development is unclear. We report here that activation of GITR signalling by anti-GITR antibody markedly enhanced the induction of both Th1 and Th2 cytokine production by naive CD4+CD25, T cells. Consistent with this observation, anti-GITR antibody significantly enhanced the expression of the key Th1 (T-bet) and Th2 (GATA3) transcription factors in vitro. Administration of anti-GITR mAb in a murine model of arthritis significantly exacerbated the severity and onset of joint inflammation with elevated production of TNF-,, IFN-,, IL-5, and collagen-specific IgG1. Administration of anti-GITR mAb also significantly exacerbated murine allergic airways inflammation with elevated production of OVA-specific IFN-,, IL-2, IL-4, IL-5, and IgE. Finally, we demonstrated that adoptive transfer of CD4+GITR+ T cells effectively abolished airway inflammation induced in SCID mice reconstituted with CD4+GITR, T cells. Our results therefore provide direct evidence that GITR can modulate both Th1- and Th2-mediated inflammatory diseases, and may be a potential target for therapeutic intervention. [source] Depletion of immature B,cells during Trypanosoma cruzi infection: involvement of myeloid cells and the cyclooxygenase pathwayEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2005Elina Zuniga Abstract The ability of a microorganism to elicit or evade B,cell responses represents a determinant factor for the final outcome of an infection. Although pathogens may subvert humoral responses at different stages of B,cell development, most studies addressing the impact of an infection on the B,cell compartment have focused on mature B,cells within peripheral lymphoid organs. Herein, we report that a protozoan infection, i.e. a Trypanosoma cruzi infection, induces a marked loss of immature B,cells in the BM, which also compromises recently emigrated B,cells in the periphery. The depletion of BM immature B,cells is associated with an increased rate of apoptosis mediated by a parasite-indirect mechanism in a Fas/FasL-independent fashion. Finally, we demonstrated that myeloid cells play an important role in B,cell depletion, since CD11b+ BM cells from infected mice secrete a product of the cyclooxygenase pathway that eliminates immature B,cells. These results highlight a previously unrecognized maneuver used by a protozoan parasite to disable B,cell generation, limiting host defense and favoring its chronic establishment. [source] Intra- and inter-allelic ordering of T cell receptor , chain gene assemblyEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2005Bernard Khor Abstract Allelic exclusion at the TCR, locus mandates that gene assembly be regulated in a manner that permits feedback inhibition of further complete TCR, rearrangements upon pre-TCR expression. Here we show that assembly of TCR, chain genes from V,, D, and J, gene segments is intra-allelically ordered, proceeding primarily through DJ,, and not VD,, intermediates. This ensures that V, to DJ, rearrangement, which can be feedback inhibited, is the final step in the assembly process. A newly assembled VDJ, rearrangement must be tested to determine if it is in-frame before V, to DJ, rearrangement is permitted on the alternate allele. This inter-allelic ordering may occur through a general inefficiency of V, to DJ, rearrangement and/or through static differences in accessibility of the two TCR, alleles. However, we find that within the regulatory context of allelic exclusion, V, to DJ, rearrangement proceeds to completion on both alleles. Furthermore, all possible VDJ, rearrangements are not completed on one allele before V, to DJ, rearrangement is initiated on the alternate allele. Together, these data support a dynamic model of inter-allelic accessibility that permits the ordered and efficient assembly of complete variable region genes on both TCR, alleles during T cell development. [source] Impaired B-1 and B-2 B,cell development and atypical splenic B,cell structures in IL-7 receptor-deficient miceEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2004Lena Erlandsson Abstract The cytokine IL-7 and its receptor are essential for normal B and T,lymphopoiesis. We have analyzed the role of this receptor in B,cell development throughout ontogeny in IL-7 receptor,,-deficient mice. We demonstrate that the IL-7 receptor becomes progressively more important with age. B,lymphopoiesis takes place, albeit at reduced levels, in fetal liver and bone marrow of young mice, but is arrested in adults. The outcome is a severe reduction, from an early age, in peripheral B,cells including follicular, marginal zone and B-1 B,cells as well as perturbed splenic B,cell structures, which are restored after adoptive transfer of normal spleen cells. We conclude that in the absence of the IL-7 receptor, the residual B,lymphopoiesis occurring early in ontogeny must be facilitated by another component, whereas the IL-7 receptor is the key factor in adults. The impairment of marginal zone and B-1 B,cells in IL-7 receptor- but not IL-7-deficient mice suggests non-redundant functions for the IL-7 receptor ligands, IL-7 and thymic stromal lymphopoietin. [source] Apoptosis via the B cell antigen receptor requires Bax translocation and involves mitochondrial depolarization, cytochrome C release, and caspase-9 activationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2004Eric Eldering Abstract Various routes to apoptosis can be active during B cell development. In a model system of mature B cells, differences in caspase-3 processing have suggested that antigen receptor (BCR)-mediated apoptosis may involve a zVAD-insensitive initiator protease(s). In search of the events leading to caspase-3 activation, we now establish that both CD95- and BCR-mediated apoptosis depend on Bax activation and cytochrome C (cytC) release. Nevertheless, the timing and caspase-dependence of mitochondrial membrane depolarization differed considerably after CD95- or BCR-triggering. To delineate events subsequent to cytC release, we compared apoptosis induced via BCR triggering and via direct mitochondrial depolarization by CCCP. In both cases, partial processing of caspase-3 was observed in the presence of zVAD. By expression in 293 cells we addressed the potential of candidate initiator caspases to function in the presence of zVAD, and found that caspase-9 efficiently processed caspase-3, while caspase-2 or ,8 were inactive. Finally, retroviral expression of dominant-negative caspase-9 inhibited both CD95- and BCR-mediated apoptosis. In conclusion, we obtained no evidence for involvement of a BCR-specific protease. Instead, our data show for the first time that the BCR-signal causes Bax translocation, followed by mitochondrial depolarization, and cytC release. Subsequent caspase-9 activation can solely account for events further downstream. [source] CREB function is required for normal thymic cellularity and post-irradiation recoveryEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2004Sven Baumann Abstract Recent generation of genetically modified Creb1 mutant mice has revealed an important role for CREB (cAMP responsive element binding protein) and the related proteins CREM (cAMP responsive element modulator) and ATF1 (activating transcription factor 1) in cell survival, in agreement with previous studies using overexpression of dominant-negative CREB (dnCREB). CREB and ATF1 are abundantly expressed in T cells and are rapidly activated by phosphorylation when T cells are stimulated through the T cell antigen receptor. We show that T cell-specific loss of CREB in mice, in combination with the loss of ATF1, results in reduced thymic cellularity and delayed thymic recovery following sublethal irradiation but no changes in T cell development or activation. These data show that loss of CREB function has specific effects on thymic T lymphocyte proliferation and homeostasis in vivo. [source] Inhibition of Notch signaling biases rat thymocyte development towards the NK cell lineageEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2004Jens van den Brandt Abstract Notch receptors are involved in directing the choice between alternative cell fates in developmental scenarios such as thymopoiesis. By pharmacological interference in rat fetal thymus organ culture we show that inhibition of Notch signaling arrests T,cell development at an early double-negative stage and is accompanied by a dramatic increase in the number of NK cells. These cells show an activated phenotype, lack recombination of the TCR, gene locus and express perforin. Similarly, in thymic lobes reconstituted with fetal liver cells, progenitors predominantly develop into NK cells both after pharmacological interference of Notch and after treatment with a recombinant rat Notch1/Fc chimera. Collectively, this identifies the lineage decision of NK/T precursor cells as an important site of Notch action in rat thymocytes. [source] | |||||||||||||||||||||||||||||||||||||