bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Models to Study Development and Function of the Human Immune System In Vivo
Authors: Legrand Nicolas , Weijer Kees , Spits Hergen 
Published: April 2014

Abstract
The study of development and function of the immune system in vivo has made intensive use of animal models, but performing such work in humans is difficult for experimental, practical, and ethical reasons. Confronted with this scientific challenge, several pioneering groups have developed in the late 1980s mouse models of human immune system development. Although these experimental approaches were proven successful and useful, they were suffering from limitations due to xenograft transplantation barriers. By reviewing the characteristics of the successive models over the last 20 years, it becomes apparent that screening of potentially interesting mouse strains and usage of combinations of genetic deficiencies has led to major advances. This is particularly true for human T cell development in the murine thymus. This review will focus on these advances and the potential future improvements that remain to be accomplished.
Cutting Edge: An Alternative Pathway of CD4+ T Cell Differentiation Is Induced Following Activation in the Absence of γ-Chain-Dependent Cytokine Signals
Authors: Mayack Shane R. , Berg Leslie J. 
Published: April 2014

Abstract
This report addresses the role of γ-chain cytokine signals in regulating CD4+ T cell differentiation following activation. Using murine CD4+ T cells lacking the Jak3 tyrosine kinase, we show that activation of these cells in the absence of γ-chain-dependent cytokine signals induces an alternative pathway of T cell differentiation. Specifically, activated Jak3−/− CD4+ T cells produce IL-10, TGF-β, and IFN-γ, but not IL-2 or IL-4, and are unable to proliferate in vitro. In addition, Jak3−/− CD4+ T cells express high levels of programmed death-1 and lymphocyte activation gene-3 and modestly suppress the proliferation of wild-type CD4+ T cells in coculture assays. Together, these features demonstrate a striking similarity between Jak3−/− CD4+ T cells and the regulatory T cells that have been shown to suppress immune responses in vitro and in vivo. We conclude that Jak3 is a critical component of signaling pathways that regulate T cell differentiation into effector vs regulatory lineages.
Cutting Edge: Influence of the TCR Vβ Domain on the Selection of Semi-Invariant NKT Cells by Endogenous Ligands
Authors: Schümann Jens , Mycko Marcin P. , Dellabona Paolo , Casorati Giulia , MacDonald H. Robson 
Published: April 2014

Abstract
Invariant Vα14 (Vα14i) NKT cells are a murine CD1d-dependent regulatory T cell subset characterized by a Vα14-Jα18 rearrangement and expression of mostly Vβ8.2 and Vβ7. Whereas the TCR Vβ domain influences the binding avidity of the Vα14i TCR for CD1d-α-galactosylceramide complexes, with Vβ8.2 conferring higher avidity binding than Vβ7, a possible impact of the TCR Vβ domain on Vα14i NKT cell selection by endogenous ligands has not been studied. In this study, we show that thymic selection of Vβ7+, but not Vβ8.2+, Vα14i NKT cells is favored in situations where endogenous ligand concentration or TCRα-chain avidity are suboptimal. Furthermore, thymic Vβ7+ Vα14i NKT cells were preferentially selected in vitro in response to CD1d-dependent presentation of endogenous ligands or exogenously added self ligand isoglobotrihexosylceramide. Collectively, our data demonstrate that the TCR Vβ domain influences the selection of Vα14i NKT cells by endogenous ligands, presumably because Vβ7 confers higher avidity binding.
IL-3-Mediated TNF Production Is Necessary for Mast Cell Development
Authors: Wright Harry V. , Bailey Daniel , Kashyap Mohit , Kepley Christopher L. , Drutskaya Marina S. , Nedospasov Sergei A. , Ryan John J. 
Published: April 2014

Abstract
Mouse mast cell development and survival are largely controlled by the cytokines IL-3 and stem cell factor (SCF). We have found that IL-3 stimulation of bone marrow cells induces the production of TNF via a PI3K- and MAPK kinase/ERK-dependent pathway. Specifically, Mac-1-positive cells were responsible for TNF production, which peaked on days 7–10 of culture and decreased rapidly thereafter. The importance of IL-3-induced TNF secretion was demonstrated by the failure of TNF-deficient bone marrow cells to survive for &gt;3 wk when cultured in IL-3 and SCF, a defect that was reversed by the addition of soluble TNF. The development of human mast cells from bone marrow progenitors was similarly hampered by the addition of TNF-blocking Abs. Cell death was due to apoptosis, which occurred with changes in mitochondrial membrane potential and caspase activation. Apoptosis appeared to be due to loss of IL-3 signaling, because TNF-deficient cells were less responsive than their wild-type counterparts to IL-3-mediated survival. In vitro cultured mast cells from TNF-deficient mice also demonstrated reduced expression of the high affinity IgE receptor, which was restored to normal levels by the addition of soluble TNF. Finally, TNF-deficient mice demonstrated a 50% reduction in peritoneal mast cell numbers, indicating that TNF is an important mast cell survival factor both in vitro and in vivo.
Role of MHC Class II on Memory B Cells in Post-Germinal Center B Cell Homeostasis and Memory Response
Authors: Shimoda Michiko , Li Tao , Pihkala Jeanene P. S. , Koni Pandelakis A. 
Published: April 2014

Abstract
We investigated the role of B cell Ag presentation in homeostasis of the memory B cell compartment in a mouse model where a conditional allele for the β-chain of MHC class II (MHC-II) is deleted in the vast majority of all B cells by cd19 promoter-mediated expression of Cre recombinase (IA-B mice). Upon T cell-dependent immunization, a small number of MHC-II+ B cells in IA-B mice dramatically expanded and restored normal albeit delayed levels of germinal center (GC) B cells with an affinity-enhancing somatic mutation to Ag. IA-B mice also established normal levels of MHC-II+ memory B cells, which, however, subsequently lost MHC-II expression by ongoing deletion of the conditional iab allele without significant loss in their number. Furthermore, in vivo Ag restimulation of MHC-II− memory B cells of IA-B mice failed to cause differentiation into plasma cells (PCs), even in the presence of Ag-specific CD4+ T cells. In addition, both numbers and Ag-specific affinity of long-lived PCs during the late post-GC phase, as well as post-GC serum affinity maturation, were significantly reduced in IA-B mice. These results support a notion that MHC-II-dependent T cell help during post-GC phase is not absolutely required for the maintenance of memory B cell frequency but is important for their differentiation into PCs and for the establishment of the long-lived PC compartment.
Human Mast Cells Undergo TRAIL-Induced Apoptosis
Authors: Berent-Maoz Beata , Piliponsky Adrian M. , Daigle Isabelle , Simon Hans-Uwe , Levi-Schaffer Francesca 
Published: April 2014

Abstract
Mast cells (MC), supposedly long-lived cells, play a key role in allergy and are important contributors to other inflammatory conditions in which they undergo hyperplasia. In humans, stem cell factor (SCF) is the main regulator of MC growth, differentiation, and survival. Although human MC numbers may also be regulated by apoptotic cell death, there have been no reports concerning the role of the extrinsic apoptotic pathway mediated by death receptors in these cells. We examined expression and function of death receptors for Fas ligand and TRAIL in human MC. Although the MC leukemia cell line HMC-1 and human lung-derived MC expressed both Fas and TRAIL-R, MC lines derived from cord blood (CBMC) expressed only TRAIL-R. Activation of TRAIL-R resulted in caspase 3-dependent apoptosis of CBMC and HMC-1. IgE-dependent activation of CBMC increased their susceptibility to TRAIL-mediated apoptosis. Results suggest that TRAIL-mediated apoptosis may be a mechanism of regulating MC survival in vivo and, potentially, for down-regulating MC hyperplasia in pathologic conditions.
Adaptive Tolerance and Clonal Anergy Are Distinct Biochemical States
Authors: Chiodetti Lynda , Choi Seeyoung , Barber Daniel L. , Schwartz Ronald H. 
Published: April 2014

AbstractAdaptive tolerance is a process by which T cells become desensitized when Ag stimulation persists following an initial immune response in vivo. To examine the biochemical changes in TCR signaling present in this state, we used a mouse model in which Rag2−/− TCR-transgenic CD4+ T cells were transferred into CD3ε−/− recipients expressing their cognate Ag. Compared with naive T cells, adaptively tolerant T cells had normal levels of TCR and slightly increased levels of CD4. Following activation with anti-TCR and anti-CD4 mAbs, the predominant signaling block in the tolerant cells was at the level of Zap70 kinase activity, which was decreased 75% in vitro. Phosphorylations of the Zap70 substrates (linker of activated T cells and phospholipase Cγ1 were also profoundly diminished. This proximal defect impacted mostly on the calcium/NFAT and NF-κB pathways, with only a modest decrease in ERK1/2 phosphorylation. This state was contrasted with T cell clonal anergy in which the RAS/MAPK pathway was preferentially impaired and there was much less inhibition of Zap70 kinase activity. Both hyporesponsive states manifested a block in IκB degradation. These results demonstrate that T cell adaptive tolerance and clonal anergy are distinct biochemical states, possibly providing T cells with two molecular mechanisms to curtail responsiveness in different biological circumstances.
Thymocyte Negative Selection Is Mediated by Protein Kinase C- and Ca2+-Dependent Transcriptional Induction of Bim
Authors: Canté-Barrett Kirsten , Gallo Elena M. , Winslow Monte M. , Crabtree Gerald R. 
Published: April 2014

Abstract
The processes of positive and negative selection in the thymus both determine the population of T cells that will enter the peripheral immune system and eliminate self-reactive T cells by apoptosis. Substantial evidence indicates that TCR signal intensity mediates this cell fate choice: low-intensity signals lead to survival and differentiation, whereas high-intensity signals generated by self-Ag lead to cell death. The molecular mechanism by which these graded signals are converted to discrete outcomes is not understood. Positive selection requires the Ca2+-dependent phosphatase calcineurin, whereas negative selection requires the proapoptotic Bcl-2 family member Bcl-2-interacting mediator of cell death (Bim). In this study, we investigated the regulation of Bim expression and the role of Ca2+ in mediating negative selection. Our results show that transcription is necessary for both negative selection and Bim induction. Surprisingly, we also found that Ca2+ is necessary for Bim induction. Induction of bim transcription appears to involve protein kinase C, but not calcineurin, JNK, p38 MAPK, or MEK. These results localize the decision point in positive vs negative selection to a step downstream of Ca2+ signaling and suggest that negative selection signals induce Ca2+-dependent bim transcription through PKC.
Frequency of Natural Regulatory CD4+CD25+ T Lymphocytes Determines the Outcome of Tolerance across Fully Mismatched MHC Barrier through Linked Recognition of Self and Allogeneic Stimuli
Authors: Fucs Rita , Jesus Joszilene T. , Souza Junior Paulo H. N. , Franco Larissa , Verícimo Mauricio , Bellio Maria , Nobrega Alberto 
Published: April 2014

Abstract
We show in this study that long-term tolerance to allogeneic skin grafts can be established in the absence of immunosuppression by the combination of the following elements: 1) augmenting the frequency of regulatory CD4+CD25+ T cells (Treg) and 2) presentation of the allogeneic stimuli through linked recognition of allo- and self-epitopes on semiallogeneic F1 APCs. BALB/c spleen cells enriched for CD4+CD25+ T lymphocytes were transferred either to BALB/c nu/nu mice or to BALB/c nu/nu previously injected with F1(BALB/c × B6.Ba) spleen cells, or else grafted with F1(BALB/c × B6.Ba) skin (chimeric BALB/c nu/nu-F1). Chimeric BALB/c nu/nu-F1 reconstituted with syngeneic CD25+-enriched spleen cells were unable to reject the previously transferred F1(BALB/c × B6.Ba) spleen cells or F1(BALB/c × B6.Ba) skin grafts, and a specific tolerance to a secondary B6 graft was obtained, with rejection of third-party CBA grafts. BALB/c nu/nu mice reconstituted only with syngeneic CD25+-enriched spleen cells rejected both B6 and CBA skin grafts. In contrast, when chimeric BALB/c nu/nu-F1 were reconstituted with spleen populations comprising normal frequencies of Treg cells, the linked recognition of allo and self resulted in breaking of self tolerance and rejection of syngeneic grafts, strongly suggesting that linked recognition works in both directions, either to establish tolerance to allo, or to break tolerance to self, the critical parameter being the relative number of Treg cells.
Ex Vivo Characterization of Allo-MHC-Restricted T Cells Specific for a Single MHC-Peptide Complex
Authors: Pittet Mikaël J. , Gati Asma , Le Gal Frederic-Anne , Bioley Gilles , Guillaume Philippe , de Smedt Magda , Plum Jean , Speiser Daniel E. , Cerottini Jean-Charles , Dietrich Pierre-Yves , Romero Pedro , Zippelius Alfred 
Published: April 2014

Abstract
Alloreactive T cells are thought to be a potentially rich source of high-avidity T cells with therapeutic potential since tolerance to self-Ags is restricted to self-MHC recognition. Given the particularly high frequency of alloreactive T cells in the peripheral immune system, we used numerous MHC class I multimers to directly visualize and isolate viral and tumor Ag-specific alloreactive CD8 T cells. In fact, all but one specificities screened were undetectable in ex vivo labeling. In this study, we report the occurrence of CD8 T cells specifically labeled with allo-HLA-A*0201/Melan-A/MART-126–35 multimers at frequencies that are in the range of 10−4 CD8 T cells and are thus detectable ex vivo by flow cytometry. We report the thymic generation and shaping of tumor Ag-specific, alloreactive T cells as well as their fate once seeded in the periphery. We show that these cells resemble their counterparts in HLA-A*0201-positive individuals, based on their structural and functional attributes.
Position-Dependent Repression and Promotion of DQB1 Intron 3 Splicing by GGGG Motifs
Authors: Královic̆ová Jana , Vor̆echovský Igor 
Published: April 2014

Abstract
Alternative splicing of HLA-DQB1 exon 4 is allele-dependent and results in variable expression of soluble DQβ. We have recently shown that differential inclusion of this exon in mature transcripts is largely due to intron 3 variants in the branch point sequence (BPS) and polypyrimidine tract. To identify additional regulatory cis-elements that contribute to haplotype-specific splicing of DQB1, we systematically examined the effect of guanosine (G) repeats on intron 3 removal. We found that the GGG or GGGG repeats generally improved splicing of DQB1 intron 3, except for those that were adjacent to the 5′ splice site where they had the opposite effect. The most prominent splicing enhancement was conferred by GGGG motifs arranged in tandem upstream of the BPS. Replacement of a G-rich segment just 5′ of the BPS with a series of random sequences markedly repressed splicing, whereas substitutions of a segment further upstream that lacked the G-rich elements and had the same size did not result in comparable splicing inhibition. Systematic mutagenesis of both suprabranch guanosine quadruplets (G4) revealed a key role of central G residues in splicing enhancement, whereas cytosines in these positions had the most prominent repressive effects. Together, these results show a significant role of tandem G4NG4 structures in splicing of both complete and truncated DQB1 intron 3, support position dependency of G repeats in splicing promotion and inhibition, and identify positively and negatively acting sequences that contribute to the haplotype-specific DQB1 expression.
Regulation of IgH Gene Assembly: Role of the Intronic Enhancer and 5′DQ52 Region in Targeting DHJH Recombination
Authors: Afshar Roshi , Pierce Steven , Bolland Daniel J. , Corcoran Anne , Oltz Eugene M. 
Published: April 2014

Abstract
The assembly of Ag receptor genes by V(D)J recombination is regulated by transcriptional promoters and enhancers which control chromatin accessibility at Ig and TCR gene segments to the RAG-1/RAG-2 recombinase complex. Paradoxically, germline deletions of the IgH enhancer (Eμ) only modestly reduce DH→JH rearrangements when assessed in peripheral B cells. However, deletion of Eμ severely impairs recombination of VH gene segments, which are located over 100 kb away. We now test two alternative explanations for the minimal effect of Eμ deletions on primary DH→JH rearrangement: 1) Accessibility at the DHJH cluster is controlled by a redundant cis-element in the absence of Eμ. One candidate for this element lies 5′ to DQ52 (PDQ52) and exhibits promoter/enhancer activity in pre-B cells. 2) In contrast to endpoint B cells, DH→JH recombination may be significantly impaired in pro-B cells from enhancer-deficient mice. To elucidate the roles of PDQ52 and Eμ in the regulation of IgH locus accessibility, we generated mice with targeted deletions of these elements. We report that the defined PDQ52 promoter is dispensable for germline transcription and recombination of the DHJH cluster. In contrast, we demonstrate that Eμ directly regulates accessibility of the DHJH region. These findings reveal a significant role for Eμ in the control mechanisms that activate IgH gene assembly and suggest that impaired VH→DHJH rearrangement in enhancer-deficient cells may be a downstream consequence of the primary block in DH→JH recombination.
Activation of Invariant NKT Cells by the Helminth Parasite Schistosoma mansoni
Authors: Mallevaey Thierry , Zanetta Jean Pierre , Faveeuw Christelle , Fontaine Josette , Maes Emmanuel , Platt Frances , Capron Monique , de-Moraes Maria Leite- , Trottein François 
Published: April 2014

Abstract
Mouse CD1d-restricted NKT cells, including invariant (i)NKT cells, are innate cells activated by glycolipid Ags and play important roles in the initiation and regulation of immune responses. Through their ability to promptly produce large amounts of Th1 and/or Th2 cytokines upon TCR engagement, iNKT cells exert crucial functions in the immune/inflammatory system during bacterial, protozoan, fungal, and viral infections. However, their roles during metazoan parasite infection, which are generally associated with strong Th2 responses, still remain elusive. In this study, we show that during the course of murine schistosomiasis, iNKT cells exhibit an activated phenotype and that following schistosome egg encounter in the liver, hepatic iNKT cells produce both IFN-γ and IL-4 in vivo. We also report that schistosome egg-sensitized dendritic cells (DCs) activate, in a CD1d-dependent manner, iNKT cells to secrete IFN-γ and IL-4 in vitro. Interestingly, transfer of egg-sensitized DCs promotes a strong Th2 response in recipient wild-type mice, but not in mice that lack iNKT cells. Engagement of TLRs in DCs is not necessary for iNKT cell stimulation in response to egg-sensitized DCs, suggesting an alternative pathway of activation. Finally, we propose that self, rather than parasite-derived, CD1d-restricted ligands are implicated in iNKT cell stimulation. Taken together, our data show for the first time that helminths can activate iNKT cells to produce immunoregulatory cytokines in vivo, enabling them to influence the adaptive immune response.
Induction of Enhanced Immunity to Intestinal Nematodes Using IL-9-Producing Dendritic Cells
Authors: Leech Melanie D. , Grencis Richard K. 
Published: April 2014

Abstract
Dendritic cells can be considered natural adjuvants and are able to act as cellular vaccines to protect against disease. Adoptive transfer of Ag-pulsed bone marrow-derived dendritic cells (BMDCs) enhanced expulsion of the intestinal nematode, Trichinella spiralis, from the small intestine. IL 9 is a critical cytokine in protective immunity to intestinal nematode infection and is believed to enhance Th2 immune responses. Deriving dendritic cells from an IL-9 transgenic (IL-9t) mouse has enabled a detailed investigation of the importance of IL-9 during Ag presentation. Indeed, IL-9t dendritic cells significantly enhanced T cell proliferation and Th2 responses and, after adoptive transfer, enhanced parasite-specific IgG1 and intestinal mastocytosis in vivo, leading to accelerated expulsion of adult worms from the intestine. Overall, this paper demonstrates that dendritic cell vaccination can be used to successfully protect the host against intestinal nematode infection and suggests that IL-9 can act as a potent type 2 adjuvant during Ag presentation and the early stages of Th2 activation.
Ceramide-Dependent Regulation of Human Epidermal Keratinocyte CD1d Expression during Terminal Differentiation
Authors: Fishelevich Rita , Malanina Alla , Luzina Irina , Atamas Sergei , Smyth Miriam J. , Porcelli Steven A. , Gaspari Anthony A. 
Published: April 2014

Abstract
Human keratinocytes (KC), when cultured under conditions to remain undifferentiated or to terminally differentiate, changed their cellular distribution of CD1d. As studied by confocal microscopy, undifferentiated KC had a pool of cytoplasmic CD1d, whereas after terminal differentiation, this molecule localized in the cell membrane, which recapitulates CD1d expression in vivo. A comparison of undifferentiated and differentiated cultured KC did not reveal any differences in the association with β2-microglobulin, invariant chain of class II MHC, or patterns of glycosylation, suggesting that these biochemical properties are not regulating the cellular distribution of CD1d. Time-course studies of CD1d gene expression indicated that KC slowly increased gene expression with CaCl2-induced terminal differentiation. Increased CD1d gene expression was dependent on ceramide synthesis, because fumonisin B1, a ceramide synthetase inhibitor, blocked the increase in CD1d gene expression during terminal differentiation. Similarly, exogenous ceramide or the ceramidase inhibitor, B13, induced CD1d gene expression by undifferentiated, but not terminally differentiated, KC. A protein kinase C-ζ (PKC-ζ) inhibitor (a pseudosubstrate oligopeptide), but not a PKC-αβ inhibitor, significantly decreased CD1d gene expression by undifferentiated or ceramide-stimulated cultured, undifferentiated KC. As expected, downstream signaling events of PKC-ζ (JNK phosphorylation and NF-κΒ accumulation in the nucleus) were also attenuated. The calcineurin phosphatase inhibitor cyclosporine A, which blocks KC terminal differentiation, also blocked CD1d gene expression by cultured KC. In conclusion, this novel function of cellular ceramides extends the importance of this class of biologically active lipids beyond that of terminal differentiation and barrier function in normal human skin.