摘要:

AbstractStimulation of T cells via the T cell receptor (TCR) activates a number of signaling pathways that are potentially involved in the elicitation of physiological responses, such as the production of cytokines. The extracellular signal‐regulated kinases (ERK) are a group of molecules activated in response to TCR ligation, whose role in T cell cytokine production is controversial. In this study, we have asked whether ERK activation is coupled to the production of a number of T cell‐derived cytokines, and whether particular cytokines are differentially affected by ERK activation. To address these questions, we have utilized a constitutively active version of the immediate upstream activator of both ERK1 and ERK2, mitogen‐activated/extracellular signal‐regulated kinase 1 (MEK1), to activate ERK signaling selectively in the absence of other TCR‐activated signaling pathways. The effect of constitutive MEK/ERK activation on T cell cytokine production was measured by transiently co‐transfecting newly activated mouse T cells with DNA encoding constitutively active MEK1 (CA‐MEK1) and the human interleukin‐2 (IL‐2) receptor α chain (hCD25), purifying hCD25+transfectants by flow‐cytometric cell sorting, and measuring the production of IL‐3, IL‐4, interferon (IFN)‐γ and granulocyte/macrophage‐colony‐stimulating factor (GM‐CSF) either in the presence or absence of ionomycin stimulation. Newly activated T cells were used in these experiments as they more closely resemble T cells activatedin vivothan do transformed T cells or long‐term established T cell clones. CA‐MEK1 expression led to constitutive ERK activation, which acted synergystically with ionomycin treatment to stimulate cytokine production. Furthermore, these experiments revealed a hierarchy of cytokine responsiveness to MEK/ERK activation, such that the production of IL‐3 was most affect

ISSN:0014-2980    

DOI:10.1002/eji.1830261002

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractSubsets of mouse natural killer (NK) cells express receptors encoded by the Ly49 gene family that recognize allelic determinants on major histocompatibility complex (MHC) class I molecules. Recognition of self class I molecules typically inhibits NK cell lytic function. The presence of NK cell subsets expressing receptors which are able to discriminate class I alleles raises the possibility that there exist mechanisms to coordinate the NK cell receptor repertoire with the class I molecules of the host. In the present study, we determined the effects of class I gene expression on the frequencies of NK cells expressing three different Ly49 receptors defined by monoclonal antibodies. We show here an MHC‐dependent skewing of NK cell subsets expressing multiple Ly49 receptors with specificity for self MHC. The results provide the first evidence that the frequencies of NK cells expressing different Ly49 receptors are determined by the host's MHC molecules. The results also extend previous findings that MHC class I expression influences the cell surface levels of each Ly49 receptor, suggesting an additional mechanism by which MHC molecules may influence the effective specificity of NK cells. Models to account for self tolerance and MHC‐controlled repertoire differences are discus

ISSN:0014-2980    

DOI:10.1002/eji.1830261003

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractT cell clones were generated from umbelical cord blood lymphocytes (UCBL) of nine newborns with atopic or nonatopic parents and their cytokine secretion profile was assessed. Both phytohemagglutinin‐induced andDermatophagoides pteronyssinus‐spetific T cell clones from newborns with atopic parents exhibited an enhanced ability to produce the Th2 cytokines interleukin (IL)‐4 and IL‐5, compared to T cell clones from newborns with nonatopic parents. In contrast, the ability to produce interferon‐γ by UCBL from the two groups of newborns was not different. Of the five children who could be followed up to 3 years after birth, four with atopic parents developed clinical and/or biological atopic manifestations, whereas one without atopic parents did not. Thus, the pronounced production of IL‐4 and IL‐5 by UCBL not only appears to be related to the atopic status of parents, but also associates with the subsequent development of atop

ISSN:0014-2980    

DOI:10.1002/eji.1830261004

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractStudies in man and mice have indicated that T cells induced duringBorrelia burgdorferiinfection are involved in the pathogenesis of the disease. We analyzed the ability ofB. burgdorferito provide co‐stimulatory signals to highly enriched normal human CD2+T lymphocytes in the presence of suboptimal concentrations of immobilized anti‐CD3 antibodies. Here we show that the lipid‐containing recombinant outer surface lipoprotein A (rlip‐OspA) ofB. burgdorferibut not its delipidated derivative rNS1‐OspA augmented CD3‐induced T cell proliferation in a dose‐dependent manner and at levels similar to that obtained with anti‐CD28 antibodies. Lipopolysaccharide had no effect in this system at any concentration tested, suggesting that the active principle of co‐stimulation is associated with the lipid moiety of rlip‐OspA and distinct from conventional lipid A. Furthermore, incubation of CD2+T cells or selected CD4+as well as CD8+subpopulations with rlip‐OspA, but not with rNS1‐OspA led to the production of interferon (IFN)‐γ, interleukin (IL)‐6 and tumor necrosis factor (TNF)‐α, but not IL‐4. In contrast, co‐stimulation of the respective T cell populations with anti‐CD28 antibodies resulted in the generation of IFN‐γ, IL‐4 and TNF‐α, but not IL‐6. This indicated that the signal transduction pathway induced by rlip‐OspA is distinct from that elicited via the CD28 receptor. Co‐stimulation of T cells with rlip‐OspA also resulted in the development of cytolytic effector cells. In light of the fact that inflamed tissues ofB. burgdorferi‐infected hosts contain blood leukocytes together with spirochetes, their degradation products, or both, these results suggest that infiltrating CD4+and CD8+T cells of any specificities, including spirochetes, autoantigens, o

ISSN:0014-2980    

DOI:10.1002/eji.1830261005

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractT cells require two distinct signals for optimal activation. One is an antigen‐specific signal and is provided by engagement of the T cell receptor (TCR). The second is an antigen‐independent signal mediated by engagement of the T cell surface molecule CD28 with members of the B7 family. To endow CD28 molecules with antibody‐type recognition, we have constructed chimeric single‐chain antibody variable fragment (scFv)‐CD28 molecules; following transfection of the genes encoding such constructs into the Jurkat human T cell line we show that they are stably expressed as functional cell surface receptors. These chimeric molecules have no apparent negative effects on the expression and signaling ability of the wild‐type CD28 and TCR/CD3 molecules. When combined with signaling via the TCR/CD3 complex, these antigen‐specific scFv‐CD28 chimeric molecules provide signals similar to those elicited by the cross‐linking of the unmodified CD28 molecules. Furthermore, the generation of double transfectants simultaneously expressing scFv‐CD28 and scFv‐CD3ζ chimeras demonstrates that antigen‐specific co‐stimulatory signals can also synergize with signals mediated through chimeric CD3ζ chains to secrete maximal levels of interleukin‐2. Overall, our results suggest that optimal, predefined antigen‐specific activation of T cells directed by the specificity

ISSN:0014-2980    

DOI:10.1002/eji.1830261006

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractTyrosine phosphorylation of proteins plays a central role in T cell activation. Mitogens or anti‐receptor antibodies have been employed to study these signaling events, but the extent to which these mimic receptor interactions with native ligands is unclear. Cytotoxic T lymphocytes can be activated for functional responses using purified, native class I ligands presented on a surface. Previous work showed that stimulation with fluid‐phase anti‐T cell receptor (TCR) monoclonal antibody (mAb) activates CD8 to mediate adhesion to class I proteins and that activated CD8 generates a co‐stimulatory signal upon binding to class I. Changes in tyrosine phosphorylation of substrates and activity of the p56lckkinase have now been examined in this two‐step process. The observed changes are small in comparison to those found using more potent nonphysiological stimuli, but may more accurately reflect the events required for activation of functional responses. Fluid‐phase anti‐TCR mAb caused increased tyrosine phosphorylation of a discrete subset of cellular substrates. Increased phosphorylation of additional substrates occurred upon CD8 binding to class I, resulting in a phosphorylation pattern comparable to that found in cells stimulated with class I alloantigen. Anti‐TCR mAb alone caused increased tyrosine phosphorylation of p56lck. When CD8 bound to class I, phosphorylation of p56lckdecreased to below the basal level found in unstimulated cells, accompanied by a substantial increase in kinase activity. These results are consistent with the two‐step model for TCR activation of CD8/class I interactions and directly demonstrate that CD8 binding to class I leads to up‐regulatio

ISSN:0014-2980    

DOI:10.1002/eji.1830261007

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractCollagen type II‐induced arthritis (CIA) is an experimental model of arthritis that has been successfully used to dissect the pathogenesis of human rheumatoid arthritis and to identify potential therapeutic targets. We have used this model to evaluate the role of T cell co‐stimulation in both disease development and progression. T cell co‐stimulation is provided by ligation of CD28 with either B7‐1 or B7‐2 present on antigen‐presenting cells and can be prevented by a soluble form of CTLA‐4 (CTLA‐4Ig) which binds with high affinity to both B7‐1 and B7‐2. We found that administration of CTLA‐4Ig at the time of immunization prevented the development of CIA and was associated with lack of lymphocyte expansion within the draining lymph node and failure to produce anti‐collagen IgG1 or IgG2a antibodies. To determine which CD28 ligand plays a more dominant role in CIA, we treated mice with monoclonal antibodies (mAb) against either B7‐1 or B7‐2. Neither anti‐B7‐1 nor anti‐B7‐2 had any effect on the course of CIA when given alone, but resulted in reduced incidence and clinical scores when given together. Interestingly, when treatment was delayed until after the onset of clinical disease, both CTLA‐4Ig or anti‐B7‐1 plus anti‐B7‐2 mAb still ameliorated disease. Effective treatment was associated with a reduction in interferon‐γ production by lymph node cells following stimulationin vitro, suggesting that Th1 responses were diminished. This study points to a critical role of CD28 co‐stimulation in the development and perpetuation of CIA in DBA/1 mice. Interestingly, it demonstrates an active role for T cells in the later stages of this disease and implicates both B7‐1 and B7

ISSN:0014-2980    

DOI:10.1002/eji.1830261008

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe CD40/gp39 pathway is known to be an important feature of B/T cell collaboration leading to T cell‐dependent activation, proliferation or differentiation of B cells. Additionally, CD40 is involved in the regulation of B cell survival and apoptosis. Recently, CD40 has been shown to be expressed functionally on non‐hematopoietic cells,i.e.endothelial cells. Here, we demonstrate that human keratinocytes (KC) culturedin vitroexpress CD40 constitutively. The surface expression of CD40 is markedly up‐regulated following stimulation with interferon (IFN)‐γ, but not with tumor necrosis factor‐α or interleukin (IL)‐1β. This process is regulated at the CD40 mRNA level as demonstrated by Northern blot analysis. Furthermore, ligation of CD40 via soluble gp39, the CD40 ligand, enhances intercellular adhesion molecule (ICAM)‐1 and Bcl‐x up‐regulation on IFN‐γ‐stimulated KC, but not lymphocyte function‐associated antigen (LFA)‐3, B7‐2, HLA‐DR, or Fas expression. The release of IL‐8 is also induced following CD40 ligation on KC. In psoriasis, a T cell‐mediated inflammatory skin disease, KC have a markedly enhanced expression of CD40. This expression co‐localizes with the expression of ICAM‐1, Bcl‐x, and an influx of CD3+T cells. These findings suggest a functional role of CD40 on KC in inflammatory skin disorders such as psoriasis and could make a therapeutic intervention by disrupting the CD40/gp39 pathway an approach to c

ISSN:0014-2980    

DOI:10.1002/eji.1830261009

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA number of T cell surface transmembrane molecules such as CD2, CD4, CD8, lymphocyte functional antigen (LFA)‐1 and CD45 are known to interact functionally with the T cell receptor (TCR) complex during T cell activation. Several previous communications have also reported physical associations between some of these molecules. On the other hand, there are indications that signaling through T cell surface molecules anchored via glycosylphosphatidylinositol (GPI), such as Thy‐1, Ly‐6 or CD59, is dependent on the TCR. Therefore, it was of interest to determine in a systematic way which T cell surface molecules are noncovalently associated with the TCR/CD3 complex and with the major intracellular signaling molecules, the protein tyrosine kinases of the Src family. To this aim, membrane proteins of human thymoma HPB‐ALL cells were solubilized in a solution of the mild detergent Brij‐58 and subjected to immunoprecipitation followed byin vitrokinase assays. Two types of large complexes containing protein tyrosine kinases were observed: the first one contained CD3 and the transmembrane proteins CD2, CD4, CD5, CD6, CD7, CD8, CD11a, CD38, CD43, CD45, CD71, CD98 and CD99 and the other contained mainly the GPI‐anchored proteins CD48, CD55, CD59 and CDw108 as well as a fraction of CD4 and CD8. The GPI‐anchored protein complexes were of larger size and lower buoyant density than the CD3 complexes. In agreement with these biochemical data, co‐cross‐linking of CD3 with most of the relevant transmembrane proteins on the surface of another T cell line, Jurkat, markedly enhanced tyrosine phosphorylation of several intracellular proteins. These data indicate the existence of at least two types of membrane microdomains of very different composition in the membranes of T cells which may play a role in signaling through different types of receptors and in functional cooperation between TCR/CD3 and various ac

ISSN:0014-2980    

DOI:10.1002/eji.1830261010

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe stimulation of human γδ T cells by mycobacteria occurs through recognition of four distinct nonpeptide phosphorylated antigens termed TUBag1–4. Among these latter, TUBag4 has already been biochemically characterized as a γ‐X derivative of 5′‐deoxythymidine triphosphate (Constant, P., Davodeau, F., Peyrat, M. A., Poquet, Y., Puzo, G., Bonneville, M. and Fournié, J.‐J.,Science1994.264: 267). However, despite chemical synthesis of weakly stimulatory nucleotide‐containing analogs, these mycobacterial compounds remained the sole nucleotide‐containing antigens actually isolated from natural sources. Here, we present the complete isolation of the TUBag3 antigen fromMycobacterium fortuitumand demonstrate that this nonpeptide molecule contains a 5′‐UTP nucleotide moiety. On selected Vγ9/Vδ2 clones, T cell responses can be triggered with nanomolar concentrations of TUBag3. Like crude mycobacterial extracts, this purified nucleotide conjugate elicits a strong polyclonal response of γδ PBL from healthy donors. Furthermore, we present evidence that this compound is distinct from the recently synthesized γ‐isopentenyl 5′‐UTP, a nucleotide conjugate of isopentenyl pyrophosphate that was found to be stimulatory for human γδ T cells (Tanaka, Y., Morita, C. T., Tanaka, Y., Nieves, E., Brenner, M. B. and Bloom, B. R.,Nature1995.375: 155). Since it appears that both mycobacterial nucleotide antigens are molecules structurally related to peculiar precursors of nucleic acid synthesis, we propose that TUBag‐reactive T cells might be specifically devoted to

ISSN:0014-2980    

DOI:10.1002/eji.1830261011

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY