bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium ionophore‐induced apoptosis of human B cells is preceded by the induced expression of early response genes
Authors: Ning Zhi‐Qiang , Murphy John J. 
Published: March 2007

AbstractWe have investigated the effects of calcium ionophore on apoptosis of Ramos human B cells. Our results show that the calcium ionophore A23187 at denned concentrations leads to apoptosis of Ramos cells. The majority of cells (> 90%) undergo apoptosis in response to ionophore. The response is rapid and nuclear condensation and DNA degradation can be detected within 2 h after addition of ionophore. In attempts to define the changes in gene expression preceding apoptosis, we investigated the expression of a panel of early response genes in these cells after ionophore addition. We show that calcium ionophore‐induced apoptosis of Ramos cells is preceded by the induced expression of a number of early response genes. These results are consistent with calcium ionophore initiating changes in gene expression which may be important in signaling these cells to undergo apoptosis.
A novel 120‐kDa antigen shared by immature human thymocytes and long‐term‐activated T cells
Authors: Fabbi Marina , Tiso Micaela , Gangemi Rosaria M. R. , Favre Anna , Demartini Paolo , Bargellesi‐Severi Antonio 
Published: March 2007

AbstractIn this study we report the characterization of monoclonal antibody (mAb) 8B4/20, raised against immature human thymocytes, that identifies a novel leukocyte antigen. The molecular characterization of the antigen by immunoprecipitation and immunoblotting yields, under nonreducing conditions, a specific band of 120 kDa which, under reducing conditions, displays a slightly lower molecular mass (110 kDa). mAb 8B4/20 detects a molecule found on the majority of thymocytes with an inverted gradient of expression when compared to CD3. It appears at high density on the CD3−/low thymocytes, at reduced density on the CD3med and double‐positive thymocytes, and is absent on CD3hi and singlepositive thymocytes and on peripheral blood T cells. Immunohistochemistry on frozen sections demonstrates cortical staining of the thymic lobules. Flow cytometric analysis of the different subsets of peripheral blood mononuclear cells shows that mAb 8B4/20 detects an antigen expressed only on CD56+/CD16+ natural killer cells and on a fraction of CD14+ monocytes. T cells, B cells, erythrocytes, granulocytes and platelets are consistently negative. The expression of the molecule on tumor cell lines does not show lineage restriction. Analysis of phytohemagglutinin plus recombinant interleukin‐2‐activated peripheral blood lymphocytes shows that mAb 8B4/20 identifies an antigen expressed on CD3+ cells by week 3 of culture. Thus, it recognizes a very late activation antigen (VLA) on mature T cells. The cell distribution and the electrophoretic pattern of the molecule identified by mAb 8B4/20 is distinct from that of known CD and of integrin/VLA molecules. Its function on thymocytes is so far unknown; however, the binding of mAb 8B4/20 to tumor lines induces changes in the morphology and adhesive properties of the 8B4/20+ cells growing in suspension. We suggest that mAb 8B4/20 recognizes a molecule that may be involved in interactions between thymocytes and other thymic structures that may be relevant for the selection process.
Beneficial effect of polyclonal immunoglobulins from malaria‐infected BALB/c mice on the lupus‐like syndrome of (NZB × NZW)F1 mice
Authors: Hentati Basma , Sato Maria Notomi , Payelle‐Brogard Béice , Avrameas Stratis , Ternynck Thérèse 
Published: March 2007

AbstractWe previously reported that infection of BALB/c mice with the parasite Plasmodium chabaudi induces high production of natural autoantibodies. Here we demonstrate that such an infection of lupus‐prone (NZB × NZW)F1 (B/W) mice retards the development of their autoimmune disease. Survival and disease hallmarks (high‐grade proteinuria and IgG anti‐DNA antibodies) were delayed for 6 months when parasite inoculation was given at either 3 or 7 months of age, i.e. before or after the onset of the clinical symptoms. Similar beneficial effects, although less pronounced, were obtained when mice were treated with a total of 800 m̈g of IgG (P‐IgG) or IgM (P‐IgM) or 300 m̈g of cryoglobulin preparations isolated from P. chabaudi‐infected BALB/c mice while similarly prepared fractions from uninfected mice had little effect. Compared to these fractions, P‐IgG and P‐IgM contained higher levels of natural antibodies bearing the D23 idiotype characteristic of polyreactive natural autoantibodies with enhanced activity against Fab and Fc fragments of IgG.In surviving mice, the level of anti‐DNA antibodies, particularly those of IgG1 isotype, were significantly decreased. Flow cytometric analysis of various T cell subsets showed that the number of cells expressing γδ T cell receptor (TcR) antigens which did not vary with age was not modified after P‐IgG or P‐IgM treatment. In contrast, the number of T cells expressing Vβ8.1,2, Vβ10 and Vβ14 TcR antigens, which increased with age, were significantly reduced. Taken together, these results indicate that parasite infection of mice induces the synthesis of populations of IgM and IgG natural autoantibodies with immunoregulatory properties and that these antibodies attempt, at least transitorily, to rescue a natural autoantibody network that is deficient in B/W mice.
Trypanosoma cruzi infection suppresses nuclear factors that bind to specific sites on the interleukin
Authors: Soong Lynn , Tarleton Rick L. 
Published: March 2007

AbstractInterleukin‐2 (II‐2) gene expression, a critical early event during T lymphocyte activation, is severely suppressed in mice infected with the protozoan parasite Trypanosoma cruzi, the causative agent of human Chagas disease. Our previous observation that reduction of IL‐2 mRNA in T cells from T. cruzi‐infected mice is not due to an increased degradation of the mRNA suggests a repression of the IL‐2 gene at the transcriptional level. In this study, we have measured the level of nuclear factors that bind to specific sites on the IL‐2 enhancer. Splenocytes and splenic T cells from acutely infected mice show a marked decrease in the level of AP‐1, and a modest decrease in the level of NF‐xB and nuclear factor of activated T cells (NF‐AT). DNA‐binding activity of Oct‐1 was least affected in T cells from infected mice. Although the basal level of AP‐1 activity is comparable in cells from uninfected and infected mice, mitogen‐induced AP‐1 activation is absent in the cells from T. cruzi‐infected mice. Sodium deoxycholate treatment slightly enhances NF‐xB‐binding activity in splenocyte nuclear and whole‐cell extracts from infected mice, suggesting that a blockage of the activation of NF‐xB is only partially responsible for the decrease in the level of NF‐xB in T cells from T. cruzi‐infected mice. These data identify the molecular basis of IL‐2 gene regulation in T. cruzi infection and suggest that T cells are anergized as a result of the infection.
Regulated expression of p150,95 (CD11c/CD18; αX/β2) and VLA‐4 (CD49d/CD29; α4/β1) integrins during myeloid cell differentiation
Authors: Bellóan Teresa , López‐Rodríguez Cristina , Rubio Miguel A. , Jochems Gijs , Bernabeu Carmelo , Corbí Angel L. 
Published: March 2007

AbstractIntegrins are a family of cell surface heterodimers which mediate both cell‐cell and cell‐extracellular matrix interactions and affect cellular differentiation through their signal transduction capacity. Integrin expression is regulated during differentiation as well as by numerous growth factors and cytokines. We have analyzed the changes in p150,95 (CD11c/CD18 or αX/β2) and VLA‐4 (CD49d/CD29 or α4/β1) integrin subunits mRNA levels that take place during the myeloid differentiation of HL60 and U937 cells, and compared them to other integrins with similar functional activities. Northern blot analysis revealed that the monocytic differentiation of U937 and HL60 cells alters the αX and α4 mRNA steady‐state levels: αX mRNA is induced de novo whereas α4 mRNA decreases to undetectable levels. Both changes were dependent on the activity of protein kinase C and were also observed upon granulocytic differentiation of HL60 cells. Parallel analysis of other integrin subunits mRNA (β1, α5, β7) demonstrated that the mRNA levels for the α subunits of the fibronectin receptors α4/β1 (VLA‐4) and α5/β1 (VLA‐5) are differentially regulated during the monocytic differentiation of myeloid cell lines, and suggested that myeloid cells express a heterodimer formed by the association of β7 with an integrin α subunit distinct from α4. Nuclear transcription assays and functional analysis of the αX and α4 promoter regions demonstrated that the transcription rate of the αX gene is considerably elevated after phorbol 12‐myristate 13‐acetate treatment of U937 cells, while that of α4 is almost unaffected, suggesting that posttranscriptional mechanisms are causing the extremely low α4 mRNA levels observed in differentiated U937 cells.
Professional presentation of antigen by activated human T cells
Authors: Barnaba Vincenzo , Watts Colin , de Boer Mark , Lane Peter , Lanzavecchia Antonio 
Published: March 2007

AbstractActivated human T cells express class II molecules, but their capacity to present soluble antigens and stimulate T cells has been repeatedly questioned. Two lines of evidence indicate that T cells may indeed function as professional antigen‐presenting cells. First, T cells that have been recently activated can efficiently capture, process and present tetanus toxoid to class II‐restricted T cell clones. This capacity correlates with the rate of class II synthesis. Second, activated T cell clones express high levels of B7, are powerful stimulators in mixed lymphocyte reactions, and their stumulatory capacity is inhibited by soluble CTLA4 or anti‐B7 antibody. Furthermore, expression of B7 can be detected in vivo on T cells from biopsies of patients with liver disease. Presentation of soluble antigen by activated T cells may play a role in the amplification of the specific response, and possibly in immunopathological states.
Determination of amino acids on agretopes of pigeon cytochrome c‐related peptides specifically bound to I‐A allelic products
Authors: Itoh Yasushi , Ogasawara Kazumasa , Takami Kimitaka , Gotohda Toshihiko , Naruse Hirohito , Good Robert A. , Onoé Kazunori 
Published: March 2007

AbstractIn our prior study it was demonstrated that residues 46 and 54 on a synthetic peptide, AEGFSYTVANKNKGIT (50V), work as an agretope (site contacts with major histocompatibility complex molecules) and residues 50 and 52 function as an epitope (site contacts with T cell receptor), when tri‐molecular complexes are formed among 50V, I‐Ab and the T cell receptor. 50V was composed of residues 43 to 58 of pigeon cytochrome c (p43‐‐58) except that the aspartic acid (D) at residue 50 was substituted by valine (V). Substitution of agretopic residues on 50V changed this I‐Ab‐binding peptide to an I‐Ak‐binding peptide, suggesting that positions 46 and 54 work as an agretope in I‐Ak‐restricted T cell responses. In the present study we examined whether residues 46 and 54 of 50V worked as agretopes in T cell responses restricted to other I‐A haplotypes. The 50V‐related peptides with phenylalanine (F) at position 46 and alanine (A) at position 54 bound tightly to I‐Ab, I‐Ad, I‐Aq and I‐As molecules and stimulated T cells most potently in mice bearing these I‐A haplotypes. In contrast, 50V‐related peptides carrying D at position 46 and A at position 54 bound most potently to I‐Ak molecules, and the peptides with arginine (R) at position 46 and A at position 54 bound most efficiently to I‐Av molecules. The present findings, thus, demonstrate that the agretopic positions on the p43‐‐58 related peptides are preserved in T cell responses restricted to each I‐A haplotype studied, and that the specific amino acids on the agretopic positions exist a priori for each I‐A allele‐specific structure.
Evidence for recombinatorial hot spots at the T cell receptor Jα locus
Authors: Rytkönen Marja , Hurwitz Julia L. , Tolonen Kirsti , Pelkonen Jukka 
Published: March 2007

AbstractThe complex genomic organization of the murine T cell receptor (TcR) δ‐α region has hindered detailed studies of α gene rearrangement and Jα gene usage in individual differentiating T cell precursors. We have isolated a novel set of Jα probes which, in combination with a few restriction enzyme digests, enable a reliable, simple and nearly complete analysis and location of any rearrangement at the Jα locus by conventional Southern blotting. The probes were used to analyze TcR α gene rearrangements in T cell hybridomas derived from an in vitro culture system that supports T cell differentiation of bone marrow cells. Our results indicate that Jα genes are unequally accessible for rearrangement and two hot spots for rearrangement could be demonstrated. In addition, only a restricted set of Jα genes was rearranged in each culture indicating that the slightly variable composition of factors can influence the recombinatorial accessibility of Jα genes. The hot spots for rearrangement were not only limited to T cells differentiating in vitro but could also be demonstrated among functional T cell clones based on the published sequence information from isolated TcR α gene rearrangements. The demonstration and the location of the hot spots for rearrangement in the T cell differentiation culture system opens up the possibility to study factors and mechanisms that regulate recombinatorial accessibility of TcR α genes.
Induction of B cell costimulatory function by recombinant murine CD40 ligand
Authors: Kennedy Mary K. , Mohler Kendall M. , Shanebeck Kurt D. , Baum Peter R. , Picha Kathleen S. , Otten‐Evans Carol A. , Janeway Charles A. , Grabstein Kenneth H. 
Published: March 2007

AbstractT cell‐dependent regulation of B cell growth and differentiation involves an interaction between CD40, a B cell surface molecule, and the CD40 ligand (CD40L) which is expressed on activated CD4+ T cells. In the current study, we show that recombinant membrane‐bound murine CD40L induces B cells to express costimulatory function for the proliferation of CD4+ Tcells. CD40L‐ or lipopolysaccharide (LPS)‐activated, but not control‐cultured B cells were strong costimulators of anti‐CD3 or alloantigen‐dependent T cell responses. The molecular interactions responsible for the increased costimulatory functions were examined by analyzing the activated B cells for changes in the expression of two costimulatory molecules, B7 and heat‐stable antigen (HSA), as well as by the use of antagonists of B7 and HSA (CTLA4.Fc and 20C9, respectively). The expression of both B7 and HSA was enhanced on B cells activated with LPS. As observed in previous studies, the costimulatory activity of the LPS‐activated B cells was dependent on both B7 and HSA and was completely inhibited in the presence of a combination of CTLA4.Fc and 20C9. In contrast, activation of B cells with CD40L induced the expression of B7 but did not enhance the expression of HSA. In addition the costimulatory activity of the CD40L‐activated B cells was partially, but not completely, inhibited by the combination of CTLA4.Fc and 20C9. These results demonstrate that CD40L regulates costimulatory function of B cells in part by inducing the expression of B7 and suggest that CD40L‐activated B cells express an additional costimulatory activity that is not associated with LPS‐activated B cells.
Differential regulation of interleukin‐6 receptors by interleukin‐6 and interferons in multiple myeloma cell lines
Authors: Lasfar Ahmed , Wietzerbin Juana , Billard Christian 
Published: March 2007

AbstractInterleukin‐6 (IL‐6) mediates pleiotropic functions through specific receptors (IL‐6R) composed of an 80‐kDa binding protein, associated with a non‐ligand binding protein (gp130) which transduces the signal. Because IL‐6 is the major tumor growth factor in multiple myeloma, we investigated the regulation of IL‐6R in two human multiple myeloma cell lines. Binding experiments with 125I‐labeled IL‐6 showed that IL‐6R were expressed at a high density on RPMI‐8226 cells (15 000 receptors/cell), but no specific binding was detected on XG‐1 cells, whose growth depends on the presence of exogenous IL‐6. However, when IL‐6 was removed from the culture medium, high‐affinity IL‐6R appeared on the surface of XG‐1 cells (5300 sites/cell). Treatment of RPMI‐8226 cells with IL‐6 reduced the number of IL‐6R without changing their affinity. This reduction was dose dependent and was not affected by acid treatment which dissociates ligand‐receptor complexes. Cross‐linking experiments showed that the formation of one IL‐6/receptor complex of 160 kDa markedly decreased upon IL‐6 treatment, while the other complex of 190 kDa became undetectable. These data provide evidence for ligand‐induced down‐regulation of membrane IL‐6R expression in myeloma cells. Treatment of RPMI‐8226 cells with interferon‐α (IFN‐α), which inhibits the growth of these cells, stimulated IL‐6R expression and increased the formation of the 160‐kDa IL‐6/receptor complex. This stimulation was specific for IFN‐α, since IFN‐γ reduced the number of IL‐6R. These data indicate that, in myeloma cells, IL‐6R are differentially regulated by IL‐6 and IFN‐α.
Identification of a signaling complex involving CD2, ζ chain and p59fyn in T lymphocytes
Authors: Gassmann Martin , Amrein Kurt E. , Flint Nicholas A. , Schraven Burkhart , Burn Paul 
Published: March 2007

AbstractCD2 is a cell surface receptor molecule which has been implicated in cell‐cell adhesion and signaling functions in T lymphocytes and natural killer cells. The mechanism by which extracellular stimuli induce CD2‐regulated signal transduction events is largely unknown. However, there is increasing evidence that in cells of hematopoietic origin several receptor‐mediated signaling mechanisms involve transmembrane polypeptides related to the CD3 ζ chain and the activation of protein tyrosine kinases. We have therefore investigated the potential involvement of ζ chain and src family protein tyrosine kinases in signal transduction pathways initiated by CD2. Using in vitro kinase assays on CD2 immunoprecipitates from detergent lysates of T lymphocytes, we identified a complex consisting of CD2, ζ chain and the src family kinases p59fyn and p56lck. Furthermore, using double indirect immunofluorescence combined with capping techniques, we have revealed such complexes in viable T lymphocytes. These findings provide evidence for a multimolecular signaling complex consisting of at least CD2, ζ chain and p59fyn in T lymphocytes and suggest a critical role for this complex in the initiation of CD2‐mediated cellular activation by regulating the activation of intracellular signaling molecules.
Regulation of RAG‐1 and CD69 expression in the thymus during positive and negative selection
Authors: Brändle Daniel , Müller Stefan , Müller Christoph , Hengartner Hans , Pircher Hanspeter 
Published: March 2007

AbstractSuccessful interaction of the T cell receptor (TCR) with major histocompatibility complex (MHC) molecules during thymic selection down‐regulates the expression of the recombination activating genes (RAG)‐1 and ‐2 in cortical thymocytes and thereby prevents further endogenous TCR α‐chain gene rearrangements (Borgulya, P., Kishi, H., Uematsu, Y. and von Boehmer, H., Cell. 1992. 69: 529‐‐537; Brändle, D., Müller, C., Rülicke, T., Hengartner, H. and Pircher, H., Proc. Natl. Acad. Sci. USA 1992. 89: 9529‐‐9533). To address the question whether down‐regulation of RAG‐1 activity represents an irreversible process we have blocked TCR‐MHC interactions of thymocytes with thymic stromal cells. Firstly, transgenic (Tg) mice expressing a virus‐specific MHC class I (H‐2Db)‐restricted TCR were injected with anti‐Db or anti‐CD8 monoclonal antibodies and RAG‐1 expression was examined by in situ hybridization on thymus sections. The results show that cortical thymocytes up‐regulated RAG‐1 expression within 24 h after antibody administration. Secondly, immature thymocytes from TCR Tg mice were released from the thymic microenvironment and cultured in vitro for 14 h in single‐cell suspension. The amount of RAG‐1 mRNA was increased sixfold in cultured cells when compared to freshly isolated thymocytes. In addition, we show that immature thymocytes from TCR transgenic mice bearing non‐selective MHC molecules (H‐2d) down‐regulated RAG‐1 expression after antigen‐induced TCR engagement. Cytofluorometric analysis further revealed that surface expression of CD69 on immature thymocytes inversely correlated with RAG‐1 expression during positive and negative selection processes.
B cells from CBA/N mice do not proliferate following ligation of CD40
Authors: Hasbold Jhagvaral , Klaus Gerry G. B. 
Published: March 2007

AbstractThe CBA/N mouse carries the X‐linked immunodeficiency xid, resulting in defective B cell development. B cells from these animals cannot mount antibody responses to type 2 T‐independent antigens, and do not synthesize DNA when stimulated with anti‐immunoglobulin (Ig) antibodies which are mitogenic for normal B cells. The primary antibody responses of CBA/N mice to T‐dependent antigens have also been reported to be abnormal. Here we describe the results of experiments which demonstrate that the B cells from these animals respond abnormally to ligation of CD40, a B cell surface molecule now known to play a key role during T cell‐B cell interactions, via its interaction with the counterligand (CD40L) expressed by activated T cells. Hence, xid B cells fail to proliferate when cultured with preactivated T helper type 2 (Th2)T cells (known to express CD40L), with a soluble CD40L‐CD8 fusion protein, or in response to monoclonal antibodies to CD40, even in the presence of IL‐4 and/or anti‐Ig reagents. However, xid B cells do receive abortive activation signals following ligation of CD40, as manifested by up‐regulation of class II major histocompatibility complex and CD23 antigens. Since the xid defect has now been identified as a point mutation in the protein tyrosine kinase Btk, our results point to an important role for this kinase in the downstream signaling cascade elicited in response to ligation of either surface Ig or CD40.
Rat interleukin‐2‐activated natural killer (A‐NK) cell‐mediated lysis is determined by the presence of CD18 on A‐NK cells and the absence of major histocompatibility complex class I on target cells
Authors: Smits Katinka M. , Kuppen Peter J. K. , Eggermont Alexander M. M. , Tamatani Takuya , Miyasaka Masayuki , Fleuren Gert Jan 
Published: March 2007

AbstractThe precise mechanism by which target cells are recognized and subsequently lysed by interleukin‐2‐activated natural killer (A‐NK) cells is poorly understood. In this study the role of major histocompatibility complex (MHC) class I and adhesion molecules in the recognition and lysis of tumor cells was investigated in a syngeneic Wag rat model. Preincubation of tumor cells with F(ab′)2 fragments of anti‐MHC class I monoclonal antibody (mAb) OX18 strongly enhanced the A‐NK cell‐mediated lysis. Also normal syngeneic cells such as T cells and A‐NK cells became highly sensitive for lysis by A‐NK cells after preincubation with mAb OX18. Two other mAb against MHC class I had no effect on lysis of target cells. These data indicate that masking of MHC class I on syngeneic tumor and normal cells by mAb OX18 is sufficient for A‐NK cells to recognize target cells as non‐self, resulting in lysis. In addition, we found that the presence of mAb against the β2 (CD18)‐integrins blocked the lysis of all tumor cell lines by A‐NK cells in 51Cr‐release assays, also when target cells were preincubated with mAb OX18. Because of the absence of CD18 on most tumor cells we concluded that a CD18‐associated integrin on A‐NK cells is essential for lysis of target cells. These results show that in this syngeneic rat model CD18 on A‐NK cells together with MHC class I on tumor cells determine A‐NK cell‐mediated lysis. Furthermore, we hypothesize that the anti‐MHC class I OX18 recognizes an epitope on rat MHC class I which is, or is very close to, the restriction element determining A‐NK cell‐mediated lysis.