bluuebunny/crossref_metadata_2025_split huggingface dataset:
A critical role for interleukin‐1 receptor accessory protein in interleukin‐1 signaling
Authors: Korherr Christian , Hofmeister Robert , Wesche Holger , Falk Werner 
Published: March 2007

AbstractInterleukin‐1 (IL‐1) is a central molecule in inflammation and immune responses whose pleiotropic activities are mediated by the type I IL‐1 receptor (IL‐1RI). The IL‐1RI alone on the cell surface is silent after binding of the ligand. We show that the recently identified IL‐1RI accessory protein (IL‐1RAcP) converts the silent into a fully functional IL‐1RI complex. Although transfection of IL‐1RAcP into IL‐1RAcP‐deficient EL4D6/76 cells did not alter the binding kinetics or dissociation constants of the 125I‐labeled IL‐1α/IL‐1RI complex, a very early event, internalization of the activated receptor complex, and a late event, IL‐1‐stimulated IL‐2 production, were successfully restored. Therefore, recruitment of IL‐1RAcP is a critical early step in the signaling cascade mediated by the IL‐1RI activation complex.
Constitutive macropinocytosis allows TAP‐dependent major histocompatibility compex class I presentation of exogenous soluble antigen by bone marrow‐derived dendritic cells
Authors: Norbury Christopher C. , Chambers Benedict J. , Prescott Alan R. , Ljunggren Hans‐Gustaf , Watts Colin 
Published: March 2007

AbstractDendritic cells expanded from mouse bone marrow (BMDC) with granulocyte/macrophage‐colony‐stimulating factor have potent T cell‐stimulatory properties both in vitro and in vivo. This has been well documented for major histocompatibility complex (MHC) class II‐restricted responses, and more recently using peptide‐loaded and protein‐pulsed DC for CD8 responses following adoptive transfer in mice. An unresolved question concerns the capacity of BMDC to present exogenous antigen on MHC class I molecules, an unconventional mode of MHC class I loading for which there is now considerable evidence, particularly in macrophages. Here, we show that BMDC exhibit high levels of macropinocytosis driven by constitutive membrane ruffling activity. Up to one‐third of actively ruffling and macropinocytosing BMDC transferred pinocytosed horseradish peroxidase into the cytosol following a 15‐min pulse, suggesting that they might be capable of presenting exogenous soluble antigen on MHC class I molecules. We show that BMDC presented exogenous ovalbumin to a T cell hybridoma more effectively, more rapidly, and at lower exogenous antigen concentrations than BM macrophages on a cell‐for‐cell basis. Presentation was TAP dependent, brefeldin A sensitive, and blocked by inhibitors of proteasomal processing, demonstrating use of the classical MHC class I pathway. Although effective presentation of exogenous antigen by BMDC occurred in the absence of agents which stimulate macropinocytosis, treatment with phorbol myristate acetate (PMA) enhanced both pinocytosis and MHC class I presentation by BMDC. Finally, PMA‐stimulated BMDC exposed to exogenous ovalbumin in vitro were able to prime an antigen‐specific cytotoxic T lymphocyte response following adoptive transfer in vivo.
Targeted disruption of the VH 81X gene: Influence on the B cell repertoire
Authors: Huetz François , Tornberg Ulla‐Carin , Malanchère Evelyne , Roes Jürgen , Carlsson Leif , Coutinho Antonio , Holmberg Dan , Rajewsky Klaus 
Published: March 2007

AbstractWe have generated a mutant mouse in which the most D‐proximal VH gene (VH81X) has been disrupted by introducing a neomycin‐resistance gene into the VH81X exon by means of gene targeting in embryonic stem cells. The mutant mice generated are unable to express the VH81X gene but appear to display a normal pattern of B cell differentiation as well as normal numbers of bone marrow and peripheral B cells from fetal life all through ontogeny. They mount normal immune responses to several different antigens tested. In contrast, the distribution of VH gene rearrangements in the VH7183 family is altered in homozygous mutant mice. Thus, the antibody repertoire of the targeted mice is modified, at least as far as the expression of VH7183 genes is concerned.
Early B cell factor binds to a site critical for λ5 core enhancer activity
Authors: Mårtensson Annica , Mårtensson Inga‐Lill 
Published: March 2007

AbstractThe pre‐B cell‐specific expression of the λ5 gene is regulated at the level of transcription. The 5′ region of the λ5 gene has been shown to contain an enhancer that activates heterologous promoters. Here, we show that this enhancer, Bλ5, also acts as a lineage‐ and tissue‐restricted enhancer on its own promoter. We define the enhancer core, bλ5, that carries around 50% of the total enhancer activity. We also demonstrate that the transcription factor early B cell factor (EBF) binds to a DNA motif in the λ5 core enhancer which is crucial for enhancer activity, suggesting that λ5 is a second target gene of EBF.
The proteasome‐specific inhibitor lactacystin blocks presentation of cytotoxic T lymphocyte epitopes in human and murine cells
Authors: Cerundolo Vincenzo , Benham Adam , Braud Veronique , Mukherjee Siddhartha , Gould Keith , Macino Beatrice , Neefjes Jacques , Townsend Alain 
Published: March 2007

AbstractWe describe the effect of the proteasome specific inhibitor lactacystin on the metabolic stability of influenza nucleoprotein (NP) and on the generation of antigens presented by human and murine class I molecules of the major histocompatibility complex to cytotoxic T lymphocytes (CTL). We show that cells treated with lactacystin fail to present influenza antigens to influenza‐specific CTL, but retain the capacity to present defined epitopes expressed as peptides intracellularly by recombinant vaccinia viruses. This block in antigen presentation can be overcome by expressing the viral protein within the lumen of the endoplasmic reticulum, confirming the specificity of lactacystin for cytosolic proteases. We also show that the effect of lactacystin on antigen presentation correlates with the block of breakdown of a rapidly degraded form of the influenza NP linked to ubiquitin. These results demonstrate that proteasome‐dependent degradation plays an important role in the cytosolic generation of CTL epitopes.
Antigen receptor‐induced apoptosis of human germinal center B cells is targeted to a centrocytic subset
Authors: Billian Gisèle , Mondière Paul , Berard Marion , Bella Chantal , Defrance Thierry 
Published: March 2007

AbstractThe outcome of the signals transduced through the B cell antigen receptor (BCR) depends both on their maturational stage and on the extent of receptor cross‐linking. It is established that the BCR‐mediated apoptosis of immature B cells represents an important mechanism for tolerance induction in the pre‐immune B cell compartment. We show here that mature germinal center (GC) B cells can re‐acquire sensitivity to BCR‐induced cell death following CD40 ligation. In contrast, neither virgin nor memory B cells become susceptible to antigen receptor‐triggered apoptosis upon CD40 stimulation, suggesting that this phenomenon may play a role in the shaping of the mature B cell repertoire in GC. Our data reveal that the death signal evoked through the BCR does not involve the Fcγ receptors, does not operate through the Fas/Fas ligand system, and can be blocked by interleukin‐4. Finally, we found that the acquisition of sensitivity to the death‐promoting effect of anti‐Ig antibodies in CD40‐stimulated GC B cell cultures correlates with the induction of a centrocytic phenotype. We propose that negative regulatory signals via the BCR may delete somatically mutated centrocytes with self‐reactivity.
MRL/lpr CD4−CD8− and CD8+ T cells, respectively, mediate Fas‐dependent and perforin cytotoxic pathways
Authors: Benihoud Karim , Bonardelle Danielle , Bobé Pierre , Kiger Nicole 
Published: March 2007

AbstractAutoimmune‐prone MRL/lpr mice, homozygous for the lpr mutation, exhibit defective apoptosis and develop generalized lymphoproliferation with the accumulation of a double‐negative (DN: CD4−CD8−) T cell population. The capacity of lpr T lymphocytes to effectuate Fas‐ and perforin‐mediated cytotoxicity was investigated. Spleen and lymph nodes cells spontaneously lyse Fas+ targets (thymocytes) through a Fas‐mediated mechanism as a consequence of their overex‐pression of Fas ligand (FasL) confirmed by semiquantitative reverse transcription (RT)‐PCR and immunoprecipitation analysis. This cytotoxicity was greatly increased after stimulation of the effectors by phorbol myristate acetate (PMA)+ionomycin. Under these conditions, MRL/lpr spleen and LN cells exhibited strong Fas‐mediated Ca2+‐independent cytotoxic activity against wild‐type Fas+ (H‐2 compatible or incompatible) thymocytes or lipopolysaccharide (LPS)‐transformed blast cells. Such Fas‐mediated cytotoxic activity was also observed with C57BL/6‐lpr, but never with wild‐type C57BL/6 or MLR+/+ effectors. Depletion experiments showed that the effector cells of this Fas‐mediated cytotoxicity were DN T cells. This subset, which represent in vivo activated T cells, can spontaneously lyse Fas+ targets by a mechanism that does not need the interaction of the T cell receptor (TCR) with major histocompatibility complex molecule plus antigen. This lytic potential is increased by PMA+ionomycin, which sends a second activation signal to these primed T cells. Therefore, the small amounts of Fas receptor expressed on MRL/lpr tissues may account for their nonspecific autoimmune attack by DN cells. In Con A‐containing medium, which allows detection of the perforin‐mediated pathway against Fas− targets, cytotoxic CD8+ effectors were detected that are able to kill lpr thymocytes via a Ca2+‐dependent pathway. Thus, in MRL/lpr mice, these CD8+ cells could constitute potent cytotoxic effectors against cells presenting antigen to their TCR.
Differentiation of human dendritic cells from monocytes in vitro
Authors: Chapuis Françoise , Rosenzwajg Michelle , Yagello Micael , Ekman Marianne , Biberfeld Peter , Gluckman Jean Claude 
Published: March 2007

AbstractSince either macrophages (Mϕ) or dendritic cells (DC) differentiate from monocytes (MO) depending on culture conditions, we investigated the relationship of the DC and Mϕ differentiation pathways. Culturing MO‐enriched blood mononuclear cells with Mϕ colony‐stimulating factor (M‐CSF) or with granulocyte/Mϕ (GM)‐CSF induced Mϕ with a different morphology and CD14/CD1a expression. In contrast, in cultures with GM‐CSF and interleukin (IL)‐4, cells rapidly became nonadherent and acquired DC morphology, ultrastructure, CD1a expression, and most DC markers; they lost membrane CD14 and CD64 and capacity of phagocytosis, displayed less CD68 than Mϕ, but retained nonspecific esterase activity. These DC directly developed from MO without proliferation inasmuch as only day 0 FACS‐sorted MO, but not small CD14− cells, differentiated into DC when cultured with GM‐CSF and IL‐4, or to Mϕ with M‐CSF. While overall cell numbers declined, DC numbers plateaued from culture day 2 onwards, indicating that most had differentiasted by then. This differentiation was radioresistant and occurred without [3H]thymidine incorporation. Commitment to differentiate into DC with GM‐CSF and IL‐4 was irreversible by day 2, since discontinuing IL‐4 at this point did not revert cells to Mϕ. Alternatively, cells rapidly converted to DC when IL‐4 was added from day 2 to cultures initiated with GM‐CSF only. If cultures were initiated with M‐CSF and switched to GM‐CSF and IL‐4 after 2 or 5 days, about half of the cells still converted to DC. Thus, the capacity of MO and even of Mϕ to differentiate into DC was conserved for at least this period. The increased capacity to stimulate the mixed leukocyte reaction correlated with the relative number of CD1a− cells at any time and under each condition tested, a confirmation that these cells functionally qualify as DC. Thus, MO and even Mϕ can be directed to differentiate into DC depending on the cytokine microenvironment.
Reduced susceptibility to Fas‐mediated apoptosis in B‐1 cells
Authors: Masuda Keiji , Wang Jiyang , Watanabe Takeshi 
Published: March 2007

AbstractElimination of activated T and B cells by Fas‐dependent apoptosis may contribute to the maintenance of peripheral tolerance. CD40 ligation was recently shown to up‐regulate Fas expression and enhance susceptibility to Fas‐mediated apoptosis in mouse splenic B cells. In the present study, we have investigated the regulation of Fas expression and Fas‐triggered apoptotis in mouse peritoneal B‐1 cells. B‐1 cells expressed a similar level of CD40 as that on B‐2 cells, and proliferated in response to a soluble CD40 ligand (CD40L)‐CD8α chimeric protein, suggesting that CD40 on B‐1 cells is functional. In contrast to B‐2 cells, B‐1 cells expressed Fas at only low levels in response to CD40L‐CD8α alone or CD40L‐CD8α+interleukin‐4, and were resistant to Fas‐mediated apoptosis following these treatments. While Fas expression could be induced in B‐1 cells to a comparable level as that in B‐2 cells by cross‐linking CD40L‐CD8α with an anti‐CD8α antibody, the sensitivity to Fas‐mediated apoptosis in B‐1 cells was significantly reduced compared with B2 cells. These results suggest that peritoneal B‐1 cells from normal mice have a lower susceptibility to Fas‐mediated apoptosis and may distinguish B‐1 from B‐2 cells. Similarly, B‐1 cells from the peritoneal cavity and spleen of autoimmune‐prone NZB mice exhibited reduced susceptibility to Fas‐mediated apoptosis relative to their B‐2 counterparts. NZB splenic B‐1 cells, however, were more susceptible to Fas‐mediated apoptosis than NZB peritoneal B‐1 cells. The results presented here raise the possibility that the reduced susceptibility to Fas‐triggered apoptosis in B‐1 cells might be an accelerating factor for the autoantibody production in NZB mice.
The generation of memory antigen‐specific cytotoxic T cell responses by CD28/CD80 interactions in the absence of antigen
Authors: Flynn Kirsten , Müllbacher Arno 
Published: March 2007

AbstractThe interaction of co‐stimulatory molecules CD80/CD86 on antigen‐presenting cells with CD28 on naive CD8+ cytotoxic T (Tc) cells is understood to be critical in the induction of Tc effectors. CD80 is capable of providing signal 2 for the activation of Tc cells, but has no effect if encountered in the absence of specific peptide/MHC complexes (signal 1). We have found that CD80 presented in vitro to resting memory viral‐immune or alloimmune Tc cells can provide sufficient stimulus for the generation of effector Tc cells in the absence of specific antigen, the peptide/MHC class I complex. Effector Tc cells generated in vitro from influenza‐ or class I alloantigen‐primed mice by co‐stimulation in the absence of antigen require exogenous interleukin (IL)‐2 signaling via the cell surface‐expressed IL‐2 receptor or, under conditions of IL‐2 blockade, exogenous IL‐7. Activation of memory Tc cells by signal 1 and 2 is independent of IL‐2 and IL‐7. Although memory influenza‐immune Tc cells did respond to CD80 in the absence of antigen, the presence of antigen +CD80 enabled an earlier induction of these Tc cells and they retained their lytic activity in vitro over a longer time period. The capacity of memory Tc cells to be activated by signal 2 alone provides one explanation for the observed heterogeneity of phenotype of memory T cells in vivo and a possible mechanism for the maintenence of memory in the absence of persisting antigen.
Differential contribution of Lck and Fyn protein tyrosine kinases to intraepithelial lymphocyte development
Authors: Page Stephanie T. , Van Oers Nicolai S. C. , Perlmutter Roger M. , Weiss Arthur , Pullen Ann M. 
Published: March 2007

AbstractThe developmental stages and the role of protein tyrosine kinases (PTK) in the maturation of CD3+CD8αα+ intraepithelial lymphocytes (IEL) have not been extensively characterized. However, comparisons of thymic and extrathymic T cell development indicate that these processes involve some distinct signaling and selection events. We used mice deficient in Lck, Fyn, or both Lck and Fyn to analyze the role that these src‐family PTK play in IEL development. In contrast to thymocyte development, we found that all IEL subsets develop in mice deficient for either kinase alone. However, lck‐/‐ animals exhibited reduced numbers of TcRαβ+CD8αα+ IEL, indicating that Lck is important in the development of these cells. Mice which lack both Lck and Fyn fail to generate TcRαβ+ IEL, suggesting that signaling through the preTcR, mediated by Lck and, to a lesser extent Fyn, is required for maturation of all TcRαβ+ IEL lineages. Interestingly, a small population of TcRγδ+CD8αα+ cells are apparent in lck‐/‐fyn‐/‐ animals, demonstrating that TcRαβ+CD8αα+ and TcRγδ+CD8αα+ IEL have distinct PTK requirements for their development or expansion. CD3−‐CD8α−CD44+ and CD3−CD8αα+CD16/32+B220+ cells comprise the majority of IEL in both lck‐/‐fyn‐/‐ and rag‐/‐ mice, while they are poorly represented in wild‐type controls. Comparison of the cell surface phenotype of these putative precursor IEL in lck‐/‐fyn‐/‐ and rag‐/‐ animals suggests that IEL maturation in these animals is arrested at an equivalent developmental stage. Overall, the data presented demonstrate that signals mediated by Lck or Fyn direct TcRαβ+CD8αα+ IEL maturation but are dispensable for the development of TcRγδ+CD8αα+ IEL.
B7‐1‐dependent co‐stimulation results in qualitatively and quantitatively different responses by CD4+ and CD8+ T cells
Authors: Deeths Matthew J. , Mescher Matthew F. 
Published: March 2007

AbstractTo characterize better the co‐stimulatory activity of native B7‐1 in the absence of other receptor/ligand interactions that might contribute to the response, B7‐1 was purified by monoclonal antibody (mAb) affinity chromatography. Immobilization of purified B7‐1 with anti‐T cell receptor (TCR) mAb on cell‐sized latex microspheres provided an effective stimulus for activation of both CD4+ and CD8+ T cells as measured by proliferation, development of effector function, and changes in motility and adhesion. The CD4+ T cell response was prolonged and resulted in efficient interleukin‐2 production and clonal expansion. In contrast, CD8+ responses were transient. Proliferation and clonal expansion peaked on days 3 and 4, coincident with maximal expression of lytic effector function, and the cells then died. These results demonstrate that B7‐1 mediated co‐stimulation is sufficient for the induction of effector function in both helper and cytotoxic T cell precursors, but suggest that B7‐1 co‐stimulation is not sufficient to sustain helper‐independent CD8+ CTL responses. When the dose responses of CD4+ and CD8+ T cells to B7‐1 were compared, CD8+ T cells were found to require higher densities of B7‐1 to attain an equivalent level of activation, suggesting that the level of expression of B7‐1 by APC may influence the development of helper or CTL responses. Finally, in contrast to results obtained by others with B7‐1 transfectants, purified B7‐1 did not provide co‐stimulation when presented on a surface separate from the TCR stimulus.
Interferon‐γ and interleukin‐4 regulate T cell interleukin‐12 responsiveness through the differential modulation of high‐affinity interleukin‐12 receptor expression
Authors: Gollob Jared A. , Kawasaki Hiroshi , Ritz Jerome 
Published: March 2007

AbstractInterferon‐γ (IFN‐γ) and interleukin‐4 (IL‐4) are mutually antagonistic cytokines that stimulate CD4+ T cells to develop into either Th1 or Th2 cells. One feature of Th2 differentiation in mice is the loss of IL‐12‐induced Jak2 and Stat4 activation, which is accompanied by the inability to produce IFN‐γ in response to IL‐12. In this report, we show that freshly isolated human T cells activated with phytohemagglutinin (PHA) in the presence of IL‐4 exhibit a greatly diminished response to IL‐12, whereas the IL‐12 response of T cells activated with PHA plus IFN‐γ is enhanced. Radiolabeled IL‐12 binding studies demonstrate that the impairment of T cell IL‐12 responsiveness by IL‐4 is associated with the down‐regulation of high‐affinity IL‐12 receptor expression. In contrast, the enhancement of IL‐12 responsiveness by IFN‐γ is associated with the up‐regulation of high‐affinity IL‐12 receptor expression. Through the use of a newly synthesized neutralizing antibody to the low‐affinity IL‐12 receptor β subunit (IL‐12Rβ), we show that neither IL‐4 nor IFN‐γ affect the expression of IL‐12Rβ, which we determine to be one of at least two low‐affinity subunits required for high‐affinity IL‐12 binding. These findings suggest that IL‐4 and IFN‐γ exert opposite effects on T cell IL‐12 responsiveness by differentially modulating the expression of low‐affinity IL‐12 receptor subunits that are distinct from IL‐12Rβ and required, together with IL‐12Rβ, for high‐affinity IL‐12 binding and IL‐12 responsiveness. This provides a basis for understanding the interplay between different cytokines at the level of cytokine receptor expression, and offers insight into one of the mechanisms governing Th1 and Th2 development.
Humoral immune response to the capsid components of recombinant adenoviruses: Routes of immunization modulate virus‐induced Ig subclass shifts
Authors: Gahéry‐Ségard Hanne , Juillard Véronique , Gaston Jesintha , Lengagne Renée , Pavirani Andrea , Boulanger Pierre , Guillet Jean‐Gérard 
Published: March 2007

AbstractThis study examines in detail the capsid‐specific humoral immune response of BALB/c mice after one single injection of a replication‐defective adenovirus. Two routes of immunization, intravenous (i.v.) and intraperitoneal (i.p.), were compared for the response induced against the adenovirus particle and the three major components of the viral capsid, hexon, penton base, and fiber. A single immunization with the replication‐defective adenovirus induces a long and persistent humoral response specific for the virus. However, the molecular components of the viral capsid are differentially recognized depending on the route of immunization. The sera from mice immunized i.p. recognized only the hexon protein and a preferential switch to the IgG2a subclass was obtained which remained stable 100 days post‐immunization. The sera obtained from mice immunized i.v. gave a more complex response. At the beginning of the response, an isotype bias toward the IgG2a subclass was observed, but the isotype distribution changed during the whole period of the response. Neutralizing activity was maximum 45 days after immunization by both routes, and no activity was detectable after 3 months. However, the i.v. serum displayed a higher neutralizing activity than the i.p. serum. The IgM antiviral antibodies appeared to be an important component of the neutralizing activity, and the two routes of immunization do not induce the same IgG isotypes to neutralize viral infectivity. Extension of these findings to human gene therapy using recombinant adenoviruses may help to characterize the precise viral protein targets of neutralizing antibodies.