摘要:

AbstractMature T cells may be produced in the thymus, or by expansion in the periphery. While thymus output of virgin cells ensures repertoire diversity, peripheral expansion increases the size of rare clones, and thus the efficiency of immune responses. We studied the role of both phenomena in the generation of the CD8+T cell pool using RAG−/−female mice expressing a transgenic T cell receptor specific for the male antigen; nude mice injected with peripheral T cells; and euthymic irradiated chimeras injected with bone marrow and mature T cells. Our results show that the total number of virgin and activated T cells, each constituting about half of the peripheral T cell pool, was regulated by homeostatic mechanisms controlling pool size. The size of each pool was regulated independently, revealing an efficient mechanism to maintain repertoire diversity while optimizing the immune respo

ISSN:0014-2980    

DOI:10.1002/eji.1830250802

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractInterleukin (IL)‐1β plays an essential role in the induction of T cell‐mediated immune responses in skin. Langerhans cells (LC), which constitutively express IL‐1β mRNA, have been assumed to be the primary source of IL‐1β in murine epidermis. The purpose of this study was to determine whether LC express mRNA for the IL‐1β converting enzyme (ICE), a protease that is required for processing pro‐IL‐1β into an active form. Here, we report that both IL‐1β and ICE mRNA are expressed by the Ia+population (i.e.LC) in murine epidermis. Moreover, murine epidermal‐derived DC lines (XS series) also express both IL‐1β and ICE mRNA, and they secrete relatively large amounts of IL‐1β following lipopolysaccharide (LPS) stimulation. Finally, LPS‐triggered IL‐1β secretion by XS cells is blocked almost completely by the ICE inhibitor acetyl‐Tyr‐Val‐Ala‐Asp‐CH2OC(O)‐[2,6‐(CF3)2]Ph. These results demonstrate that LC are the primary source of IL‐1β within the epidermis, and suggest that the proinflammatory role of IL‐1β may b

ISSN:0014-2980    

DOI:10.1002/eji.1830250803

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractCD69 is the earliest inducible cell surface glycoprotein acquired during lymphoid activation bothin vitroandin vivounder physiological conditions and inflammation. This molecule is involved in lymphocyte proliferation, and functions as a signal‐transmitting receptor in T and B lymphocytes, NK cells and platelets. Molecular cloning of CD69 cDNA revealed that this antigen is a type‐II integral membrane protein with a C‐type lectin domain in the extracellular region. The expression time course of CD69 mRNA has previously been reported to be transient, peaking around 3 h after induction in T lymphocytes, and declining to nearly resting levels by 8 h. We describe herein studies on the stability of the CD69 mRNA in phorbol ester‐activated T lymphocytes. The level of CD69 mRNA in these cells declined rapidly with a half‐life of less than 60 min. This finding is consistent with the presence of several AU‐rich sequence motifs in the 3′ untranslated region (3′UTR), which have been implicated in the selective destabilization of short‐lived mRNA of mammalian cytokines, and proto‐oncogenes. We have therefore introduced a fragment of the 3′UTR of the human CD69 cDNA, which contains the AU‐rich sequence motifs, into the 3′UTR of the rabbit β‐globin gene. This inserted sequence causes the otherwise stable β‐globin mRNA to become unstablein vivo. A similar destabilizing effect is observed when the 51‐nucleotide AU sequence from the mRNA of the human cytokine granulocyte/macrophage colony‐stimulating factor is used as a positive control. Furthermore, the introduction of 194‐bp fragment from the CD69 3′UTR containing most of the AU‐rich motifs was sufficient to induce the destabilizing effect. We propose that the selective degradation pathway involved in the regulation of the expression of cytokines and proto‐oncogenes is implicated in the rapid degradation of CD69 mRNA in activated T lymphocytes. This pathway may constitute a general mechanism to regulate the expression of inducible m

ISSN:0014-2980    

DOI:10.1002/eji.1830250804

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA ligand for CD30 has been recently cloned, and has been shown to have sequence homology with the tumor necrosis factor family of cytokines. CD30 ligand (CD30L) was found to be induced on helper T cell clones, and its receptor was expressed on freshly isolated and activated murine B cells. Recombinant murine CD30L was found to share many functional properties with CD40 ligand (CD40L) in the regulation of murine B cell growth and differentiationin vitro. CD30L stimulated B cell proliferation, antigen‐specific antibody production, and polyclonal immunoglobulin secretion in a cytokine‐dependent manner. In particular, the stimulation of B cell proliferation by CD30L required interleukin (IL)‐4 and IL‐5, induction of anti‐sheep red blood cell antibody‐secreting B cells by CD30L required IL‐2 and IL‐5, and optimal induction of polyclonal immunoglobulin secretion required IL‐4 and IL‐5. Under these conditions, the polyclonal secretion of IgGl, IgA, IgG3 and IgE was induced. The induction of immunoglobulin secretion by CD30L was independent of CD40L, as B cells from CD40L deficient‐mice responded normally to CD30L treatment. We conclude that CD30L is a potent mediator of B cell growth and differentiationin vitroand may play a role in cognate T cel

ISSN:0014-2980    

DOI:10.1002/eji.1830250805

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractAnalysis of λ light chain use in normal mice is made difficult by the dominantxlight chain repertoire. We produced mice rendered deficient inxlight chain expression by gene targeting and focused on questions concerned with the generation of λ light chain diversity. Whilst these mice compensate thexdeficiency with increased λ titers, and their Ig level is therefore not significantly reduced, they show major differences in immunization titers, germinal center (GC) development and somatic hypermutation. After immunization, using antigens that elicit a restricted IgL response in normal mice, we obtained in thex−/−mice elevated primary antibody titers but a subsequent lack in titer increase after repeated antigen challenge. Analysis of the Peyer's patches (PP) revealed a dramatically reduced cell content with rather small but highly active GC. Flow cytometric analysis showed different cell populations in the PP with enriched peanut agglutinin (PNA)hi/CD45R(B220)+B cells, implying that the apparent compensation for the lack ofxlight chain expression involves the GC microenvironment in cell selection, the initiation of hypermutation and high affinity expansion. The three Vλ genes, V1, V2 and Vx, are mutated in the GC B cells, but show no junctional diversity. In contrast, a reduced rate of Vλ hypermutation is found in the hybridoma antibodies, which appears to reflect a selection bias rather than structural constraints. However, mechanisms of somatic mutation and specificity selection can operate with equal efficiency on the few

ISSN:0014-2980    

DOI:10.1002/eji.1830250806

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring ontogeny, the skin is progressively populated by major histocompatibility complex class II‐negative dendritic cell (DC) precursors that then mature into efficient antigen‐presenting cells (APC). To characterize these DC progenitors better, we generated myeloid cell lines from fetal mouse skin by infecting cell suspensions with a retroviral vector carrying anenvAKR‐mycMH2fusion gene. These cells, represented by the line FSDC, displayed a dendritic morphology and their proliferation in serum‐free medium was promoted by granulocyte/macrophage colony‐stimulating factor (GM‐CSF), but not macrophage‐CSF. FSDC expressed strong surface‐membrane ATP/ADPase activity, intracellular staining for 2A1 antigen, and a surface phenotype consistent with a myeloid precursor: H‐2d.b+, I‐Ad.b+, CD54+, CD11b+, CD11c+, 2.4G2+, F4/80+, CD44+, 2F8+, ER‐MP 12−, Sca‐1+, Sca‐2+, NLDC‐145−, B7.2+, B7.1−, J11d−, B220−, Thy‐1−, and CD3−. FSDC stimulated poorly allogeneic or syngeneic T cells in the primary mixed‐leukocyte reaction, and markedly increased this function after treatment with GM‐CSF, GM‐CSF and interleukin (IL)‐4 or interferon‐γ (IFN‐γ); in contrast, stem cell factor, IL‐1α and tumor necrosis factor‐α had no effect. Preculture with IFN‐γ was required for presentation of haptens to primed T cellsin vitro. However, FSDC, even after cytokine activation, were less potent APC than adult epidermal Langerhans cells in both of the above assays. Finally, FSDC derivatized with haptens and injected either intravenously or subcutaneously could efficiently induce contact sensitivity responses in naive syngeneic mice. The results indicate that fetal mouse skin is colonized by myeloid precursors possessing a macrophage/immature DC‐like surface phenotype and priming capacityin vivo. These cells need further differentiation and activation signals (

ISSN:0014-2980    

DOI:10.1002/eji.1830250807

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe major histocompatibility complex (MHC)‐encoded transporter associated with antigen processing (TAP) delivers cytosolic peptides to the lumen of the endoplasmic reticulum (ER) for presentation by MHC class I molecules. For the rat, it has been demonstrated that TAP polymorphism results in the selection of different sets of peptides, the nature of the C terminus being of particular importance. Here, we investigated whether TAP polymorphism in mice and humans has functional consequences for transport of peptide sets variable at the C‐terminal residues. Using cell lines of H‐2d, H‐2k, and H‐2dxkhaplotype and a panel of human lymphoblastoid cell lines expressing eight different TAP alleles, we detected species‐specific transport patterns, but no significant influence of TAP polymorphism on peptide selection. In addition, peptides with different core sequences were translocated to the same extent by different TAP. These results suggest that a major contribution of human TAP polymorphism to disease progression and autoimmunity is not

ISSN:0014-2980    

DOI:10.1002/eji.1830250808

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe regulation of interleukin (IL)‐2 gene expression has been investigated mainly in T lymphocytes, the predominant producers of IL‐2. However, B cells can also synthesize IL‐2. In the present study we analyzed the control of IL‐2 promoter activity in Epstein‐Barr virus (EBV)‐transformed B cell clones which are capable of secreting IL‐2 at a low level after stimulation with phorbol 12‐myristate 13‐acetate and the Ca2+ionophore ionomycin. Transient transfections using reporter constructs with multiples of transcription factor binding sites from the IL‐2 promoter [distal nuclear factor (NF)‐AT, proximal NF‐AT, AP‐1/Octamer (UPS) or NF‐ϰB (TCEd) sites] were performed. In EBV‐transformed B clones, the ϰB site exerted the strongest inducible activity; the NF‐AT binding sites showed either no or only weak activity compared to Jurkat T cells. An IL‐2 promoter bearing a defective NF‐ϰB site was completely inactive in EBV‐B cells, white it still had activity in Jurkat T cells. In seven EBV‐B cell clones or lines differing in their capacity to secrete IL‐2, the activity of the IL‐2 promoter correlated well with the status of IL‐2 secretion. Similarly, a human immunodeficiency virus promoter, whose activity is controlled through ϰB factors, was found to be active in the IL‐2‐producing EBV‐B cells, but inactive in the non‐IL‐2‐producing cells. Electrophoretic mobility shift assays using protein extracts from EBV‐B cells and the IL‐2 NF‐ϰB probe revealed the constitutive generation of ϰB complexes in IL‐2‐secreting cells consisting mainly of heterodimeric p50/p65 complexes. A weaker ϰB complex formation and faster‐migrating complexes were detected in non‐IL‐2‐secreting cells. These results demonstrate that the IL‐2 NF‐ϰB site is indispensable for the activity of the IL‐2 promoter in EBV‐transformed B cells, whereas

ISSN:0014-2980    

DOI:10.1002/eji.1830250809

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractTumor necrosis factor (TNF) and lymphotoxin α (LTα) are closely related cytokines which bind with nearly identical affinities to the same pair of cell surface receptors, p55 and p75TNFR. Therefore it is assumed that TNF and LTα are redundant cytokines. This study, however, demonstrates that TNF and LTα differ significantly with regard to their mitogenic and cytotoxic potentials. LTα's superior mitogenic effect could be explained by its formation of a more stable trimer. In contrast to the TNF trimer, which disintegrated under physiological conditions into biologically inactive monomers, the LTα trimer remained stable for several days. Accordingly, LTα more effectively induced fibroblast growth which demands long‐term presence of the cytokine. TNF's superior cytotoxicity, which requires only short‐term impact of the cytokine, could be attributed to a distinct interaction with the human p55TNFR. This was demonstrated in NIH 3T3 cells transfected with the human p55TNFR, where cytotoxicity is mediated exclusively by the transfected receptor. Although the p55TNFR had virtually identical affinities for TNF and LTα, as defined by Scatchard analysis, it nevertheless discriminated between binding of each cytokine and showed a 200‐fold enhanced cytotoxicity me

ISSN:0014-2980    

DOI:10.1002/eji.1830250810

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractCD95 (Fas antigen/APO‐1) is up‐regulated in activated lymphocytes, and monoclonal antibody (mAb) to CD95 induces apoptosis. HLA class II molecules play a key role in antigen presentation, ligation of which induces signal transduction. We examined 18 lymphoid cell lines (15 B cell and 3 T cell lines) to investigate the effects of ligation of HLA class II molecules on CD95‐mediated apoptosis. All of the five immature B cell lines were sensitive to anti‐CD95 mAb, and ligation of HLA class II molecules promoted CD95‐mediated apoptosis. In seven B‐blastoid cell lines, two Burkitt lines were resistant to anti‐CD95 mAb in spite of high expression of CD95. In three of five non‐Burkitt B‐blastoid lines, CD95‐mediated apoptosis was augmented by treatment with anti‐HLA class II mAb, while the other two lines lacking CD95 were resistant to anti‐CD95 mAb. Three plasmacytic cell lines showed CD95‐mediated apoptosis, but enhancement by anti‐HLA class II mAb was slight in one cell line and was not observed in the other two lines. Out of three HLA class II antigen‐positive T cell lines, CD95‐mediated apoptosis was observed to some degree in one cell line but was not promoted by the treatment with anti‐HLA class II mAb, and the other two cell lines were resistant to anti‐CD95 mAb. Ligation of HLA class II molecules did not alter CD95 expression in the five cell lines examined, except Su‐DHL‐4 originated from a follicular lymphoma, which showed slight up‐regulation. Taken together, ligation of HLA class II molecules apparently promotes CD95‐mediated apoptosis in immature B cells and non‐Burkitt B blasts. These findings highlight the role of HLA class II molecules in CD95‐mediated apoptosis, which may facilitate rapid clearance of functionally useless cells from the immune system and mig

ISSN:0014-2980    

DOI:10.1002/eji.1830250811

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY