bluuebunny/crossref_metadata_2025_split huggingface dataset:
Up‐regulated recombination‐activating gene expression in slg− variants of a human mature B cell line undergoing secondary Igλ, rearrangements in cell culture
Authors: Stiernholm Niclas B. J. , Berinstein Neil L. 
Published: March 2007

AbstractTo study the role of surface immunoglobulin (sIg) expression in the control of rearrangement activity at the Ig light chain loci, we established rare sIg− clones (λ−) from a human sIg+ B cell line (μl+). Upon expansion of these sIg− clones, surface immunofluorescence analysis revealed a gradual emergence of sIg+ subpopulations, differing from the original tumor cell line both in their idiotypes and Cλ isotypes. DNA analysis revealed that this sIg heterogeneity resulted from a process of ongoing Igλ, rearrangements. That is, one of the Igλ rearrangements in the parental cell line was replaced by novel Igλ rearrangements in the sIg− clones, which in turn were replaced by yet additional Igλ rearrangements in the sIg+ variants. Northern analysis demonstrated that while the expression of the recombination‐activating genes RAG1 and RAG2 was relatively low in the parental cell line, their expression was significantly increased in both the sλ g+ variants and their sIg+ progenies. We thus describe a human mature B cell line, in which differential RAG expression allows sIg heterogeneity to be generated through secondary Igλ gene rearrangements. Our results indicate that the induction of RAG expression may be inversely associated with sIg expression, but that sIg expression, alone, is not sufficient to down‐regulate this expression.
Immune response in mouse and malaria‐exposed humans to peptides derived from Pfl1‐1, a highly repetitive megadalton protein of Plasmodium falciparum
Authors: Scherf Artur , Behr Charlotte , Sarthou Jean‐Louis , Pla Marika , Rogier Christophe , Trape Jean‐François , Silva Luiz Pereira Da , Dubois Philippe 
Published: March 2007

AbstractWe have investigated the immune response against the Plasmodium falciparum gametocyte‐specific antigen Pf11‐1. This megadalton parasite molecule has been implicated in the process of erythrocyte rupture during gametogenesis. The molecule is composed in great part of degenerated nonapeptide motifs which are tandemly repeated several hundred times. A computer algorithm searching for T sites predicted that the entire repeat region of the Pf11‐1 represents potential T cell antigenic major histocompatibility complex class II‐binding sites. To test this hypothesis, synthetic peptides corresponding to two nonamer subtype repeats, differing only at two amino acid positions, were used to immunize congenic mouse strains. Both peptides were shown to contain both B and T cell epitopes. The immune response is restricted to the H‐2d andH‐2khaplotypes. The T cell response against the peptides appeared to be highly specific, clearly discriminating between the two similar nonamer repeat sequences, whereas the humoral response produced cross‐reacting antibodies. We also investigated the humoral and T cell reactivities of P. falciparum‐primed individuals in West Africa against the synthetic Pf11‐1 peptides. Among 51 individuals 35 had antibodies to at least one of the two peptides and a majority of them (28) had antibodies reacting with both peptides. The cellular response was analyzed by [3H] thymidine incorporation or interferon‐y release. There was considerable variation in the response to the two peptides. Among the human samples 36% responded to one repeat subtype, while only 13% responded to the second subtype. Interestingly, in individual donors the T cell response to both peptides are associated, suggesting that, as shown for mice, the response is restricted by a genetic element. The data obtained on the two subtypes of the nonamer repeat region suggest that the entire Pfll‐1 molecule might induce an unusually heterogenous B and T cell response during natural infection in man.
The invasin protein of Yersinia spp. provides co‐stimulatory activity to human T cells through interaction with β integrins
Authors: Brett Sara J. , Mazurov Alexey V. , Charles Ian G. , Tite John P. 
Published: March 2007

AbstractThe invasin proteins of Yersinia spp. are outer membrane proteins which are involved in the penetration of these bacteria into mammalian cells (Cell 1990. 60: 861). Invasin binds to several different β integrins with extremely high affinity, the integrin‐binding domain of invasin has been mapped to the C‐terminal 192 amino‐acids of the molecule (J. Biol. Chem. 1991.266:24367). Expression of this fragment alone on the cell surface of non‐invasive bacteria is enough to confer the invasive phenotype on these strains (EMBOJ. 1990. 9:1979). Here we show that the carboxy‐terminal 192 amino acids of invasin expressed as a fusion protein with the maltose binding protein of E. coli is capable of delivering co‐stimulatory signals to human T cells through the β integrins. Co‐stimulation was assayed by the ability of invasin to augment the response of highly purified CD4+ and CD8+ T cells to co‐immobilized anti‐CD3 antibody. Antibody blocking studies indicated that the co‐stimulation was mediated through β integrins. The proliferation induced by co‐stimulation of CD4+ T cells was accompanied by the synthesis of the cytokines tumor necrosis factor‐a and interferon‐y, whereas the activation of CD8+ T cells led to the generation of cytotoxic effectors. The region of the invasin molecule involved in T cell activation was further mapped using synthetic peptides. A region of the invasin molecule containing the residues TAKSKKFP‐SY could substitute for invasin in T cell activation. The co‐stimulation by peptide could also be inhibited by anti‐integrin antibodies. The observation that an outer membrane protein of a bacterium which is associated with reactive arthritis and other autoimmune spondyloarthropathies can act as a T cell co‐stimulus may have implications for the etiology of these diseases.
T cell receptor targeting to thymic cortical epithelial cells in vivo induces survival, activation and differentiation of immature thymocytes
Authors: Müller Klaus‐Peter , Kyewski Bruno A. 
Published: March 2007

AbstractWe report that targeting of T cell receptors (TcR) to non‐major histocompatibility complex (MHC) molecules on thymic cortical epithelial cells by hybrid antibodies in vivo and in fetal thymic organ cultures results in phenotypic and functional differentiation of thymocytes. A single pulse with hybrid antibodies rescues immature, CD4/8 double‐positive thymocytes from their programmed death in vivo, induces expression of the early activation antigen CD69 followed by TcR up‐regulation, concomitant down‐regulation of CD8 or CD4 and their conversion to functional mature T cells by day 3. This temporal sequence of maturation only affects small thymocytes without co‐induction of blastogenesis. TcR targeting to MHC class II‐positive epithelial cells predominantly induces CD4‐positive T cells. This generation of CD4 single‐positive T cells occurs also in MHC class II‐deficient mice and thus is independent of CD4‐MHC class II interactions. Moreover, in the presence of a specific deleting antigen (Mls 1a),TcR targeting results in transient activation of immature thymocytes, however, not in subsequent TcR (Vβ6) up‐regulation and development of single‐positive T cells. Our findings imply that TcR cross‐linking to cortical epithelial cells is sufficient to confer a differentiation signal to immature thymocytes. Futhermore, this approach distinguishes two independent TcR‐mediated intrathymic events: activation and subsequent deletion of the same thymocyte subset.
Antigen‐presenting cells in adoptively transferred and spontaneous autoimmune diabetes
Authors: Lo David , Reilly Christina R. , Scott Bernadette , Liblau Roland , McDevitt Hugh O. , Burkly Linda C. 
Published: March 2007

AbstractHistological techniques were used to identify antigen‐presenting cells (APC) in adoptively transferred diabetes in NOD mice and Ins‐HA transgenic mice, and in spontaneously diabetic NOD mice. In adoptively transferred disease, CD4+ Tcells and F4/80+ macrophages dominated early infiltrates. By contrast, in spontaneously developing diabetes in NOD mice, lymphocytic infiltrates appeared to be well organized around a network of VCAM‐1+ NLDC‐145+ ICAM‐1+ dendritic cells. Thus, the primary APC spontaneous autoimmune disease appears to be the strongly stimulatory dendritic cell rather than the normally resident macrophage. Next, we used chimeric animals to demonstrate that insulitis and diabetes could occur even when responding T cells were unable to recognize islet‐specific antigen directly on β cells. Altogether, the results demonstrate that immune‐mediated damage does not require direct contact between CD4+ T cells and β cells. Moreover, despite the induction of ICAM‐1, VCAM‐1, and class II on vascular endothelium near islet infiltrates, these experiments show that recruitment of lymphocytes occurs even when antigen presentation is not possible on vascular endothelium.
TAP2‐defective RMA‐S cells present Sendai virus antigen to cytotoxic T lymphocytes
Authors: Zhou Xianzheng , Glas Rickard , Momburg Frank , Hämmerling Günter J. , Jondal Mikael , Ljunggren Hans‐Gustaf 
Published: March 2007

AbstractThe murine antigen‐processing‐defective mutant cell line RMA‐S is leaky in the presentation of certain endogenously synthesized minor histocompatibility and viral antigens to major histocompatibility complex (MHC) class I‐restricted cytotoxic T lymphocytes (CTL). The viral antigens include influenza virus nucleoprotein, vesicular stomatitis virus (VSV) nucleocapsid and Rauscher murine leukemia virus (MuLV) antigen. Here we demonstrate Sendai virus antigen presentation by the HAM2 (murine TAP2, transporter associated with antigen presentation type 2)‐defective RMA‐S cell line and compare antigen presentation after restoration of the defect by murine TAP1/2 gene transfection. Kinetic studies revealed that RMA‐S cells required 2‐3 h longer incubation and approximately 10 times higher doses of Sendai virus to reach the same level of killing as the RMA parental line. After transfection of RMA‐S cells with the murine TAP1/2 gene, Sendai virus antigen presentation was restored to levels of the RMA wild‐type line with regard to time of virus infection and dose of virus needed for sensitizing target cells. The presentation of Sendai virus antigen in RMA‐S cells was sensitive to brefeldin A (BFA), suggesting that the presentation was mediated via the endogenous pathway. Our findings comfirmed leakiness of antigen presentation in RMA‐S cells and extended it to Sendai virus. The results underscored the role for intact expression of the TAP 1/2 molecules for efficient MHC class I‐mediated antigen presentation.
Antigen processing mutant T2 cells present viral antigen restricted through H‐2K
Authors: Zhou Xianzheng , Glas Rickard , Liu Tianmin , Ljunggren Hans‐Gustaf , Jondal Mikael 
Published: March 2007

AbstractCytotoxic T lymphocytes (CTL) recognize foreign antigens as short peptides presented by class I molecules of the major histocompatibility complex (MHC). T2 cells are profoundly defective in the presentation of endogenously synthesized antigens to CTL due to a deletion of MHC class II‐encoded genes for transporters associated with antigen presentation (TAP1/TAP2). Surprisingly, we here demonstrate that T2 cells, after infection with Sendai virus, are readily killed by H‐2Kb restricted CD8+ T cells. In contrast to classical class I‐mediated antigen presentation, the presentation of Sendai virus antigen inT2Kb cells is brefeldin A (BFA) insensitive. The present findings may suggest the presence of an alternative pathway for MHC class I‐mediated antigen presentation in T2 cells.
Cytokine production and heterogeneity of primary stromal cells that support B lymphopoiesis
Authors: Witte Pamela L. , Frantsve Lisa M. , Hergott Muriel , Rahbe Sandra M. 
Published: March 2007

AbstractMany reports document that bone marrow stromal cells or their cytokine products can influence the formation of B cells in vitro. Most of this data comes from studies using lines or clones of stromal cells after multiple passage in culture, which could alter gene expression. Our aim in the present study was to determine which cytokines are produced by normal stromal cells under conditions that promote B lymphopoiesis. Primary cultured stromal cells were isolated on FACS from active Whitlock cultures. These cells proved to be relatively homogeneous in expression of cell surface antigens (CD44, VCAM‐1, MECA10, and a molecule marked by hamster anti‐mouse 8.28 monoclonal antibody). RNA from unselected Whitlock cultured adherent cells and sorted stromal cells from the same cultures were subjected to reverse transcriptase polymerase chain reaction to assess constitutive expression of several cytokine genes. Transcripts for interleukin‐1β (IL‐1β), IL‐7, macrophage (M)‐colony‐stimulating factor (CSF), stem cell growth factor (SCGF), insulin‐like growth factor 1 (IGF‐1) and occasionally leukemia inhibitory factor were detected in RNA from intact cultures. Messages for IL‐7, M‐CSF, and SCGF were selectively contained within the isolated stromal cell fraction; whereas, IL‐1β was found solely within the non‐stromal cell fraction. IGF‐1 was transcribed by both stromal cells and macrophages in Whitlock cultures. No evidence was found for constitutive expression of IL‐1 α, IL‐4, IL‐6, or granulocyte‐macrophage‐CSF. This is in contrast to some reported stromal cell lines and clones. To determine if all primary stromal cells from active lymphopoietic cultures produced IL‐7, the isolated cells were stained to reveal cytoplasmic IL‐7 protein. A majority of the cells produced IL‐7, but about 20 % had no detectable IL‐7 protein. Taken together, our results suggest that the primary stromal cells are a distinguishable cell type but functional subsets may exist. In regard to the differences in IL‐7 production, the primary cell phenotype appears to mirror at least one division noted among the stromal cell lines.
Association of a 70‐kDa tyrosine phosphoprotein with the CD16:ζ:γ complex expressed in human natural killer cells
Authors: Vivier Eric , da Silva Antonio J. , Ackerly Melissa , Levine Herbert , Rudd Christopher E. , Anderson Paul 
Published: March 2007

AbstractThe CD16: ζ: γ receptor complex allows natural killer (NK) cells to recognize and eliminate antibody‐coated target cells. Whereas the ectodomain of CD16 is the receptor for Fcγ domains of immunoglobulins, disulfide‐linked homo‐ and heterodimers composed of ζ and γ are required for the cell surface expression, and signal transduction properties of the complex. Engagement of CD16 activates the tyrosine kinase pathway, which induces the tyrosine phosphorylation of several substrates, including the ζ subunit and the phospholipase C γ‐1 and γ‐2 isoforms. Here we show that CD 16 stimulation of either peripheral blood NK cells, leukemic NK cells, or Jurkat transformants expressing a CD16:ζ:γ receptor complex, results in the tyrosine phosphorylation of a 70 kDa ζ‐associated protein (pp70). Similarly, a 70‐kDa ζ‐associated phosphoprotein in T cells has been shown to be a tyrosine kinase (ZAP‐70). Peptide mapping analysis indicates that the 70‐kDa ζ‐associated phosphoproteins from T cells and NK cells are structurally indistinguishable. We conclude that the CD16:ζ:γ complex may use a ZAP‐70‐related non‐receptor tyrosine kinase, in the CD16 signaling cascade leading to NK cell activation.
Regulation of perforin gene expression in a T cell hybrid with inducible cytolytic activity
Authors: García‐Sanz José A. , Podack Eckhard R. 
Published: March 2007

AbstractA mouse × rat T cell hybrid (PC60) that does not require interleukin (IL)‐2 for proliferation, was used as a model to study regulation of perforin gene expression. Perforin mRNA is barely detectable in non‐induced PC60 cells; however, a 30‐fold induction is observed after stimulation with IL‐1 alone. Peak perforin mRNA levels were reached after 10 h of induction with IL‐1, and these levels were maintained for as long as the stimulus was present. IL‐2 by itself has no detectable effect. However, in combination with IL‐1 it shows the same induction kinetics as IL‐1 alone for the first 10 h, subsequently there is synergism (100‐fold induction) between IL‐1 and IL‐2. The induction response was mainly due to increased transcriptional rates of the perforin gene, and require newly synthesized proteins. The half‐life of perforin mRNA in this system is about 5 h. In addition, we confirm the existence of two types of mouse perforin mRNA that differ in their 5′ untranslated regions, and show evidence that both mRNA are translated in vivo with similar efficiencies.
Cachexia and the acute‐phase protein response in inflammation are regulated by interleukin‐6
Authors: Oldenburg Hester S. A. , Rogy Michael A. , Lazarus Douglas D. , van Zee Kimberly J. , Keeler Bonnie P. , Chizzonite Richard A. , Lowry Stephen F. , Moldawer Lyle L. 
Published: March 2007

AbstractCachexia and the acute‐phase response are common manifestations of inflammation and are presumed to be the product of increased synthesis and release of cytokines, including tumor necrosis factor (TNF), interleukin‐1 (IL‐1) and interleukin‐6 (IL‐6). IL‐1 receptor blockade has been previously shown to attenuate the weight loss, anorexia and acute‐phase protein responses associated with a turpentine abscess. However, IL‐1 receptor blockade was also associated with a reduced plasma IL‐6 response, suggesting that the benefit achieved by IL‐1 receptor blockade may be mediated by reduced systemic IL‐6 production. To gain a better understanding of the role of IL‐6 in this model of inflammation, C57BL/6 mice were passively immunized with either a monoclonal anti‐IL‐6 antibody (20F3), an anti‐IL‐1 type I receptor monoclonal antibody (35F5), a non‐immune rat IgG, or a combined therapy of 35F5 and 20F3, before receiving a sterile turpentine abscess. IL‐6 or IL‐1 receptor blockade equally spared body weight and food intake. Compared to IL‐1 receptor blockade, passive immunization against IL‐6 further reduced the hepatic acute‐phase protein response, as represented by serum amyloid P and complement 3. Combined blockade of IL‐6 and IL‐1 receptor did not result in a further sparing of body weights or improvement of food intake. These results confirm that IL‐1 contributes to host cachexia and the acute‐phase response following a turpentine abscess, but also show that these actions are dependent upon an IL‐6 response. We onclude that the influence of IL‐1 on cachexia and the acute‐phase response is mediated, at least in part, through IL‐6 and, thus, IL‐6 may play a pivotal role in the cachexia and acute‐phase response to inflammation.
Regulation of T cell production in T cell receptor transgenic mice
Authors: Kelly Katherine A. , Pircher Hanspeter , von Boehmer Harald , Davisand Mark M. , Scollay Roland 
Published: March 2007

AbstractThe thymus produces many more cells than it releases into the periphery. According to generally accepted models of T cell development most of this loss occurs in the thymic cortex, among CD4+8+ thymocytes. An interesting situation arises in the case of T cell receptor (TcR) transgenic mice in which all cells can potentially be positively selected, leading to a theoretical increase of about 30‐fold in the survival rate of CD4+8+ cells and in their transition to mature CD4+8−or CD4−8+ thymocytes. This in turn should lead to a 30‐fold increase in the size of the thymic medulla, in the emigration rate and in the size of the peripheral Tcell pool. Increases in medullary or peripheral pool sizes of this magnitude are not seen in TcR transgenic mice. The question was therefore asked whether some form of homeostatic process regulated the size of the mature T cell pool and at what level it might operate. In this report we demonstrate that the increased rate of double‐positive to single‐positive transition in the TcR transgenic mice is directly reflected in an increased emigration rate, and that the medulla seems to be relatively efficient regardless of the number of cells passing through it. However, the potential increases in emigrant numbers in TcR transgenic mice are offset by the reduced size of the CD4+8+ thymocyte pool. It would appear then that regulation of T cell production, if it occurs, probably does so through regulation of the size of the CD4+8+ thymocyte pool. Mechanisms for regulation of this kind are not yet known.
Diversity of expressed V and J regions of immunoglobulin light chains in Xenopus laevis
Authors: Stewart Sue E. , Du Pasquier Louis , Steiner Lisa A. 
Published: March 2007

AbstractIn Xenopus laevis, two immunoglobulin light chain isotypes, designated L1 or ϱ and L2 or σ, have been identified. The genomic organization of the L1 locus has been described previously: a constant (C) gene segment is preceded by a joining (J) gene segment; in addition, there are many cross‐hybridizing variable (V) gene segments. To evaluate the extent of sequence diversity of L1 V regions, we screened three cDNA libraries, constructed from mitogen‐stimulated Xenopus splenocytes, with probes for the C or the J gene segment. Eighteen cDNA clones that contain complete or truncated V regions were chosen for sequence analysis. The C regions of all clones are identical or nearly identical to the genomic C gene segment; the V regions are greater than 80 % identical in nucleotide sequence and are presumably derived from a single family of V gene segments. Although framework regions are nearly identical, complementarity‐determining regions are quite diverse. The expressed J segments fall into distinct groups, suggesting the presence of more than one germ‐line J segment. Therefore, a genomic library was screened with a J region probe. A clone overlapping with the previously identified J‐ C clone, and containing four additional J gene segments, was isolated. All five J gene segments are very similar and three are identical in nucleotide sequence. Each of the three distinct germ‐line J sequences is represented in the set of cDNA clones, suggesting that combinatorial diversification occurs; imprecision of V‐J joining also appears to contribute to variability. Overall, these results suggest that the immunoglobulin repertoire in this species is not significantly restricted by a limitation in the diversity of light chain V regions.
Interleukin‐6 production in “normal” and HTLV‐1 tax‐expressing brain‐specific endothelial cells
Authors: Rott Ortwin , Tontsch Ulrike , Fleischer Bernhard , Cash Evelyne 
Published: March 2007

AbstractAbnormal cytokine production can contribute in many instances to the development of pathology. Our study focuses on the regulation of interleukin (IL)‐6 production in vitro in brain‐specific endothelial cells (BEC) under physiological conditions and in a model of human T leukemia virus‐1 (HTLV‐1) infection. IL‐6 production was strongly up‐regulated in a dose‐dependent mode upon exposure to recombinant IL‐1β although nearly not detectable in unstimulated BEC. This induction of IL‐6 production could be achieved by reagents known to increase intracellular levels of cAMP, such as for skolin, prostaglandin E or pentoxifylline. Furthermore, transcription and production of IL‐6 was inducible by addition of dibutyryl cAMP, but not by addition of calcium ionophores or diacylglycerol. To assess a potential role of HTLV‐1‐infected BEC in the pathogenesis of tropical spastic paraparesis (TSP), the HTLV‐1 tax gene was expressed in BEC. Tax gene‐expressing BEC produced constitutively very high amounts of IL‐6, which were not longer hyperinducible by IL‐ip or cAMP derivates. Our results indicate that HTLV‐1 tax induces hyperproduction of IL‐6 in brain‐specific endothelial cells directly by an intracellular mechanism which subsequently renders IL‐6 production independent of exogenous stimuli or activators of (cAMP‐dependent) second messenger levels. On the basis of these findings we suggest that tax‐mediated hyperactivation of IL‐6 production in BEC contributes to elevated IL‐6 levels found in serum and cerebrospinal fluid of patients with TSP and might have a significance in the immune pathogenesis of the disease.