摘要:

AbstractCBA/N (xid) mice have a point mutation in Bruton's tyrosine kinase (btk), which results in their failure to respond to T‐independent type 2 (TI‐2) antigens, and to several B cell mitogens [most notably anti‐immunoglobulin (Ig)]in vitro. They have reduced numbers of peripheral (B2) B cells, which are regarded as being phenotypically and functionally immature. We show here that adult CBA/N mice in fact have two distinct B cell populations: some 60% of the cells are CD23+HSAlosIgDhiand hence resemble recirculating, follicular (RF) B cells from normal mice, except that they are sIgMhi. The remaining 40% of xid B cells are CD23−HSAhisIgD−/loand resemble immature transitional (TR) B cells. TR B cells from xid mice do not synthesize DNA when cultured with lipopolysaccharide (LPS), whereas those from normal mice do so. Only the RF cells from either xid or normal mice proliferate in response to ligation of CD40. In neonatal normal mice the emergence of mitogen responsiveness followed the chronological sequence LPS → anti‐CD40 → anti‐Ig ≈ anti‐CD38. The same developmental sequence was seen with B cells from xid mice (for LPS and anti‐CD40), but it occurred at a significantly slower tempo and this correlated with the later appearance of RF‐type cells. TR xid B cells express very low levels of bcl‐2 and we conclude that these cells resemble very immature (bone marrow) B cells, rather than normal transitional cells. We, therefore, propose that the xid mutation imposes a multistage brake on B cell differentiation in the mouse. The available data suggest that btk is required for the positive selection of B cells throughout their differentiation in the periphery. This in turn implies that low level signaling via surface Ig is needed throughout this process in order for peripheral B cells to

ISSN:0014-2980    

DOI:10.1002/eji.1830271102

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIt is generally recognized that activation through membrane effector molecules such as CD40 or the B cell receptor (BCR) is mandatory to allow B cells to proliferate and differentiate into antibody (Ab)‐secreting cells in response to cytokines. We show here that purified tonsillar B cells can be stimulated directly by a cytokine combination to proliferate and secrete immunoglobulins when cultures are performed at high cell density. The contact‐mediated activation of B cells in this experimental system is strongly inhibited both by anti‐very late antigen (VLA)‐4 monoclonal Ab and by a peptide containing the LDV sequence specifically recognized by the α4 integrin binding site. These reagents also significantly suppressed the B cell responses elicited by engagement of the BCR or CD40. Our data reveal that memory B cells but not virgin or germinal center B cells are sensitive to the direct stimulatory effect of cytokines in high‐density cultures. Finally, we found that the dual expression of the α and β chains of VLA‐4 is a distinctive feature of the memory B cell population. Collectively, our findings support the notion that VLA‐4‐dependent homotypic B cell interactions can mediate a co‐stimulatory signal to human memory B cells and might participate in the B cell activation triggered thro

ISSN:0014-2980    

DOI:10.1002/eji.1830271103

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractOmenn's syndrome (OS) is characterized by erythrodermia, hepatosplenomegaly, lymphadenopathy, hypereosinophilia and elevated IgE levels associated with increased susceptibility to severe infections. Peripheral blood T cells, though usually present in normal number, show an activated phenotype (including an increased expression of CD95/Fas), a Th2 pattern of cytokine secretion and defective proliferative response to mitogens. In this report, we demonstrate that T cells from patients with OS undergo an excessive cell deathin vitroresulting from two mechanisms. First, a substantial number of peripheral blood lymphocytes from OS patients die in unstimulated cultures (p= 0.009vs.healthy controls). This spontaneous apoptosis is associated with reduced expression of bcl‐2 gene product (p<0.05) and can be prevented by addition of interleukin (IL)‐2 (which also prevents down‐modulation of bcl‐2), while is independent from CD95 signaling. Second, lymphocytes from OS patients are highly susceptible to activation‐induced cell death (AICD) induced with mitogens. This mechanism is largely independent from IL‐2, while it can be significantly inhibited blocking CD95 with an IgG2b monoclonal antibody (mAb). The dependence of AICD from signals transduced via CD95 was confirmed showing that cross‐linking CD95 with an IgM mAb induces a higher cell death in purified CD4+CD45RO+cells from OS patients than in controls (comparable for CD95 expression). Both mechanisms of cell death observed in this study result from lymphocyte hyperactivation occurringin vivoin these patients and may contribute to functional T cell

ISSN:0014-2980    

DOI:10.1002/eji.1830271104

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSignaling via the T cell receptor (TCR)/CD3 complex of pre‐activated T cells induces apoptosis. Such an activation‐induced cell death (AICD) is thought to play an important role in the regulation of cellular immune responses. In this study we analyzed pathways of AICD by using human T cells transformed byHerpesvirus saimiri. These growth‐transformed T cells show the phenotype of activated mature T cells and continue to express a functionally intact TCR. We show that humanH. saimiri‐transformed T cell clones readily undergo cell death upon signaling via the TCR/CD3 complex or via phorbol 12‐myristate 13‐acetate (PMA) + ionomycin. The AICD inH. saimiri‐transformed T cells was detectable a few hours after activation and it was not affected by the presence of interleukin (IL)‐2 or by anti‐CD4 cross‐linking. However, AICD required tyrosine phosphorylation, since it could be blocked by herbimycin A. Cyclosporin A (CsA) did not block the development of AICD, but other consequences of activation inH. saimiri‐transformed T cells like the production of interferon‐γ. Surprisingly, the development of AICD was not reduced by neutralizing antibodies to tumor necrosis factor (TNF)‐α or blocking antibodies directed to CD95 (Fas, APO‐1), althoughH. saimiri‐transformed T cells were sensitive to CD95 ligation. To confirm that this form of AICD is really independent of CD95, we have established anH. saimiri‐transformed T cell line from a patient with a homozygous deletion in the CD95 gene. This CD95‐deficient T cell line was as sensitive to AICD as other CD95‐expressingH. saimiri‐transformed T cells. In conclusion, we describe here a type of AICD inH. saimiri‐transformed T cells that is independent of CD95 and TNF‐α, not sensitive to CsA, but requires tyrosine phosphorylation. This system should be useful for the inv

ISSN:0014-2980    

DOI:10.1002/eji.1830271105

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractRapamycin (RAPA) is a potent immunosuppressive drug, and certain of its direct or indirect targets might be of vital importance to the regulation of an immune response. In this study, we used differential hybridization to search for human genes whose expression was sensitive to RAPA. Seven RAPA‐sensitive genes were found and one of them encoded a protein with high homology to the α subunit of a proteasome activator (PA28α). This gene was later found to code for the β subunit of the proteasome activator (PA28β). Activated T and B cells had up‐regulated PA28β expression at the mRNA level. Such up‐regulation could be suppressed by RAPA, FK506, and cyclosporin A. RAPA and FK506 also repressed the up‐regulated PA28α messages in phytohemagglutinin (PHA)‐stimulated T cells. At the protein level, RAPA inhibited PA28α and PA28β in the activated T cells according to immunoblotting and confocal microscopy. Probably as a consequence, there was a fourfold increase of proteasome activities in the peripheral blood mononuclear cell lysate after the PHA activation. RAPA could inhibit the enhanced part of the proteasome activity. Considering the critical role played by the proteasome in degrading regulatory proteins, our data suggest that the proteasome activator is a relevant and important downstream target of rapamycin, and that the immune response could be modulated through the activity

ISSN:0014-2980    

DOI:10.1002/eji.1830271106

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractInterferon‐γ inducing factor (IGIF) is a recently identified cytokine which stimulates the production of interferon‐γ (IFN‐γ) by T cells and enhances natural killer (NK) cell cytolytic activity. Protein fold recognition, structure prediction and comparative modeling have revealed that IGIF is a member of the interleukin (IL)‐1 cytokine family and has prompted the designation IL‐1γ. Here we report functional similarities between members of the IL‐1 family by comparing the effects of IL‐1α, IL‐1β and IGIF on NK cell production of IFN‐γ. All three IL‐1 types enhanced NK cell production of IFN‐γ when induced by IL‐2 or IL‐12, although at high concentrations (>10 ng/ml), IGIF was five‐ to tenfold more potent than IL‐1α or IL‐1β. This effect correlated with enhanced levels of mRNA for IFN‐γ when NK cells were stimulated with IGIF plus IL‐12. In contrast to IL‐12 and IL‐2, the ability of IGIF to stimulate NK cell production of IFN‐γ was not increased by IL‐1α or IL‐1β. The ability of IGIF to enhance IFN‐γ production was independent of the type I and type II IL‐1 receptors or the IL‐1R accessory protein. Together, these results identify IGIF as a potent stimulator of NK cell production of IFN‐γ and demonstrate that the effect of IGIF on NK cell production of IFN‐

ISSN:0014-2980    

DOI:10.1002/eji.1830271107

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractHere we describe a Rho‐mediated apoptosis suppression pathway driven by Bcl‐2 expression in the interleukin (IL)‐4‐ or IL‐2‐dependent murine T cell line TS1αβ. IL‐2, but not IL‐4, induces Bcl‐2 expression through RhoA activation which is inhibited by the specific Rho family inhibitor,Clostridium difficileToxin B, as well as by a dominant negative RhoA mutant. Using transient transfections of RhoA mutants tagged with the vesicular stomatitis virus glycoprotein, we show that a constitutively active RhoA mutant induces Bcl‐2 expression and prevents apoptosis upon IL‐4 withdrawal. Finally, we have identified the signaling pathway involved together with RhoA in Bcl‐2 induction and show compelling evidence for the implication of phosphatidylinositol 3 ki

ISSN:0014-2980    

DOI:10.1002/eji.1830271108

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractTumor necrosis factor (TNF)‐α and platelet‐activating factor (PAF) are important mediators of inflammatory reactions, and their release is controlled by a positive feedback network. However, the regulatory mechanisms underlying the interaction of these two molecules are unknown. Within 10 min of the injection of lipopolysaccharide (LPS) into C57BL/6 mice, effects inducible by PAF such as anaphylactic shock‐like symptoms, disseminated intravascular coagulation, and hemorrhage in renal medullae were observed, and all these pathological changes were prevented by the PAF antagonist, BN 50739. The plasma level of PAF after LPS injection reached a peak at 5 min. TNF‐α gene expression was evident 20 min after LPS injection and was maximal at 40 min, and the level of serum TNF‐α reached a peak at 1 h. Pretreatment with BN 50739 inhibited LPS‐induced TNF‐α gene expression and protein synthesis in a dose‐dependent manner. Injection of PAF or treatment of the macrophage cell line, J774A.1, with PAF activated the transcription factor, nuclear factor (NF)‐xB, which is essential for inducible TNF‐α transcription. The activation of NF‐xB by PAF preceded the LPS‐mediated TNF‐α gene expression. Pretreatment with BN 50739 inhibited LPS‐induced mobilization of NF‐xB in a dose‐dependent mannerin vivoas well asin vitro. These data suggest that PAF, which is released immediately or shortly after LPS injection, induces the expression of

ISSN:0014-2980    

DOI:10.1002/eji.1830271109

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe biological basis for the pleiotropic activity of extracellular human immunodeficiency virus (HIV)‐1 Tat protein on lymphoid T cell survival is not well understood. We have here demonstrated that the addition in culture of 0.1–10 nM Tat protein to 36‐h serum‐starved lymphoblastoid Jurkat T cells rapidly stimulates the catalytic activity of phosphatidylinositol 3‐kinase (PI 3‐K). The peak of activation was observed 30 min after Tat addition. Extracellular Tat also stimulated the catalytic activity of the Akt/PKB kinase, a major target of PI 3‐K lipid products. Pretreatment of serum‐starved Jurkat cells with 100 nM wortmannin (WT) or 10 μM LY294002, two unrelated pharmacological inhibitors of PI 3‐K, markedly suppressed the catalytic activity of both PI 3‐K and Akt/PKB in Jurkat cells. Moreover, at low concentrations (0.1–1 nM), extracellular Tat showed a small but reproducible protection of Jurkat cells from apoptosis induced by serum deprivation (p<0.05), while the combination of Tat plus 100 nM WT significantly (p<0.05) increased the percentage of apoptosis with respect to cells left untreated or treated with Tat alone. Taken together, these data suggest that the anti‐apoptotic activity of low concentrations of Tat protein on Jurkat cells is mediated by a

ISSN:0014-2980    

DOI:10.1002/eji.1830271110

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe majority of peripheral blood γδ T cells in human adults expresses T cell receptors (TCR) with identical V regions (Vγ9 and Vδ2). These Vγ9Vδ2 T cells recognize the major histocompatibility complex (MHC) class I‐deficient B cell line Daudi and broadly distributed nonpeptidic antigens present in bacteria and parasites. Here we show that unlike αβ or Vγ9−γδ T cells, the majority of Vγ9Vδ2T cells harbor natural killer inhibitory receptors (KIR) (mainly CD94/NKG2A heterodimers), which are known to deliver inhibitory signals upon interaction with MHC class I molecules. Within Vγ9δ2 T cells, KIR were mainly expressed by clones exhibiting a strong lytic activity against Daudi cells. In stark contrast, almost all Vγ9Vδ2 T cell clones devoid of killing activity were KIR−, thus suggesting a coordinate acquisition of KIR and cytotoxic activity within Vγ9Vδ2 T cells. In functional terms, KIR inhibited lysis of MHC class I‐positive tumor B cell lines by Vγ9Vδ2 cytotoxic T lymphocytes (CTL) and raised their threshold of activation by microbial antigens presented by MHC class I‐positive cells. Furthermore, masking KIR or MHC class I molecules revealed a TCR‐dependent recognition by Vγ9Vδ2 CTL of ligands expressed by activated T lymphocytes, including the effector cells themselves. Taken together, these results suggest a general implication of Vγ9Vδ2 T cells in immune response regulation and a central role of KIR in

ISSN:0014-2980    

DOI:10.1002/eji.1830271111

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY