摘要:

AbstractWe analyzed the mode of antigen presentation of an endogenous antigen localized in the cytoplasm or in the mitochondria.Pseudomonas aeruginosaPAO leucine‐, isoleucine‐, valine‐binding protein (LIVAT‐BP) encoded by thebraCgene was used as a model antigen. Using mouse BALB/3T3 cells, we established two LIVAT‐BP transfectants by transfection of a plasmid harboring the intactbraC or braCgene fused with the mitochondrial transport signal derived from the yeastCOXIVgene. One of the resulting transfectants, BC‐15, expressed LIVAT‐BP in the cytoplasm, while YZ‐710 cells expressed LIVAT‐BP in the mitochondria. The splenic effector cells derived from BALB/c mice primed with BC‐15 cells exhibited cytotoxic T lymphocyte (CTL) activity against BC‐15 cells, but not against YZ‐710 cells, whereas splenic effector cells primed with YZ‐710 cells exhibited CTL activity against YZ‐710 cells, but not against BC‐15 cells. Neither group of splenic effector cells showed CTL activity against parental BALB/3T3 cells. These CTL belonged to the CD8+αβ T cell subset. Furthermore, we observed that the CTL activity against BC‐15 cells or YZ‐710 cells was blocked with anti‐H2‐KdmAb, but not with anti‐H2‐Ddor H2‐LdmAb. The CTL against BC‐15 or YZ‐710 cells could kill parental BALB/3T3 cells in the presence of peptides produced by alkali lysis of the LIVAT‐BP. suggesting that these CTL indeed recognized the peptide(s) derived from LIVAT‐BP. We determined that the epitope for the CTL against BC‐15 cells was QYGEGIATEV, corresponding to residues 162–171, and that the epitope recognized by the CTL against YZ‐710 cells was GYKLIFRTI, corresponding to residues 123–131 of LIVAT‐BP, respectively. Thus, we show here that epitope selection for MHC class I expression is affe

ISSN:0014-2980    

DOI:10.1002/eji.1830270202

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractNatural killer (NK) cells are bone marrow‐derived large granular lymphocytes that express the CD56 surface antigen. The CD56brightNK subset represents approximately 10 % of all NK cells and is thought to be the least differentiated NK cell component in blood. The most mature NK cell expresses CD56 at low density and CD16 (FcRγIII) at high density, whereas CD56brightNK cells either lack CD 16 (CD56brightCD16−) or express it at low density (CD56brightCD16dim). c‐kit is a tyrosine kinase receptor which is expressed on both CD34+hemato‐poietic precursor cells and CD56brightNK cells. In the current study, we characterize interleukin (IL)‐2 receptor (IL‐2R) and c‐kit expression in each of the CD56brightsubsets. Both the CD56brightCD16−and CD56brightCD16dimNK subsets express the high‐affinity IL‐2R and the c‐kit receptor when isolated from fresh blood. However, each CD56brightNK cell subset has distinct functional responses to IL‐2, the c‐kit ligand (KL), or both. Activation of the high‐affinity IL‐2R on CD56brightCD16−NK cells induces a proliferative response that is significantly weaker than that observed in the CD56brightCD16dimNK cell subset. Incubation of the CD56brightCD16−NK cell subset with KL significantly enhances IL‐2‐induced proliferation, while KL has no such effect on the CD56brightCD16dimNK subset. Activation of the high‐affinity IL‐2R in both CD56brightsubsets induces lymphokine‐activated killer (LAK) activity, but the addition of KL has no effect on LAK activity. Co‐stimulation of either CD56brightsubset with IL‐12 and concentrations of IL‐2 that only saturate the high‐affinity IL‐2R induces substantial interferon (IFN)‐γ production. The addition of KL to this co‐stimulatory signal enhances IFN‐γ production in both CD56brightNK subsets. The distinct functional responses to IL‐2 and KL seen in the CD56brightCD16−and CD56brightCD16dimNK subsets provide insight into IL‐2R signaling and suggest that e

ISSN:0014-2980    

DOI:10.1002/eji.1830270203

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractRecent evidence indicates that conventional T cells are generated by the mainstream of T cell differentiation in the thymus and acquire a high density of T cell receptor expression (i.e.TCRhi). In contrast, primordial T cells (or NK1.1+T cells) are generated by the extrathymic pathways or an alternative intrathymic pathway and express an intermediate density of TCR (i.e.TCRint). To obtain further evidence, it was examined how thymus grafting influenced the distribution of T cell populations in athymic nude mice. When BALB/cnu/numice were engrafted with thymocyte‐depleted BALB/c+/+ fetal thymi, two changes emerged after grafting: nude mice generated TCRhicellsde novoin the periphery as well as in the grafted thymi, and the absolute number of interleukin‐2 receptor β chain+TCRintcells increased prominently in number in the periphery. Among thymic hormones tested, the administration of thymosin α induced a slight expansion of CD3intcells in nude mice. To examine a possible interaction of TCRintcells with TCRhicells in the periphery, B6nu/numice (Ly5.2+) were injected with TCRhicells purified from the spleen of B6 Ly5.1 congenic mice. In this case, TCRint(Ly5.2+) cells expanded well in all tested organs of nude mice. These results suggest that the generation of TCRhicells is absolutely dependent on the thymus and that TCRintcells expand under the influence of the thymus (humoral) and due to interaction with thymus‐derived conventional

ISSN:0014-2980    

DOI:10.1002/eji.1830270204

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSusceptibility to spondyloarthropaties is strongly associated with some HLA‐B27 alleles. Evidence suggests a direct pathogenic role for the B27 molecules which possibly present an arthritogenic peptide to the T cells. If this hypothesis is true, B27 subtypes that differ structurally but are disease‐associated ought to be capable of presenting such peptide(s), while non‐disease‐associated ones would not. We have recently described a B27 subtype, B*2709, and shown its absence in ankylosing spondylitis (AS) patients. Here, we show the elution and sequence of peptides from HLA‐B*2709 molecules. Similar to other B27 subtypes, these peptides are mainly nonamers with an Arg at position P2. Comparison of the C‐terminal anchors of peptides eluted from B*2702 and B*2705 with those eluted from B*2709 reveals that, while B*2702 and B*2705 have a broader specificity, B*2709 molecules appear to only accept C‐terminal hydrophobic residues. A common feature shared by the two caucasoid AS‐associated subtypes (B*2702 and B*2705) but different from B*2709, is the presence of a Tyr as peptide C‐terminal anchor. The substitution of Val for Tyr at the C terminus in one of the eluted peptides greatly reduces the binding to B*2709 molecules. This finding suggests Tyr as a discriminative amino acid allowed at the C terminus of peptides bound to the AS‐associated B27 subtypes, but not to those which are not

ISSN:0014-2980    

DOI:10.1002/eji.1830270205

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractWe investigated the effector mechanisms operating during the rejection of a transplantable solid lymphoma E.G7 (H‐2b) which expresses the gene encoding chicken ovalbumin (OVA). Anti‐OVA cytotoxic T lymphocytes (CTL) completely and specifically protected animals from the onset of, but could not eradicate established, E.G7 tumors. The growth of the same lymphoma was also effectively prevented by the antibody GK1.5, whose target molecule, CD4, was expressed on E.G7 cellsin vivo.Furthermore, GK1.5 was able to eradicate established solid E.G7 tumors. GK1.5‐mediated tumor elimination was due to its antitumor activity, and not to the elimination of regulatory CD4+cells, based on unimpaired tumor growth in the absence of GK1.5 in animals that genetically lack CD4 T cells.In vitro, GK1.5 did not kill tumor cells: complement activation or apoptosis induction were not evident.In vivo, GK1.5‐mediated tumor regression did not depend on natural killer cells, but it absolutely required CD8+cells and intact Fcγ receptor. We conclude that, in the E.G7 model, the collaboration of antibody and CTL immunity was crucial for the successful immunotherapy of established tumors. The mechanism of this collaboration is d

ISSN:0014-2980    

DOI:10.1002/eji.1830270206

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractCD45‐AP is a recently identified CD45‐associated protein. The two proteins interact specifically through their respective transmembrane segments. Northern hybridization analysis of CD45+T lymphocytes and their CD45−variants demonstrated that the production of CD45‐AP and CD45 mRNA is regulated independently. On the other hand, Western blotting analysis indicated that the CD45‐AP protein has a shorter half‐life in the absence of CD45 in three out of four variants. Similar analysis of various types of leukocytes demonstrated that CD45‐AP is expressed in T, B, and pre‐B cells, but not in plasma cells or cells of the monocyte/macrophage lineage. Two forms of CD45‐AP mRNA exist in all types of CD45‐AP‐expressing lymphocytes analyzed. One form corresponds to the previously reported CD45‐AP cDNA and the other form encodes an additional 12 amino acids at the N terminus. The two CD45‐AP proteins are identical in their capacity for specific binding to CD45, but employ different mechanisms for endoplasmic reticul

ISSN:0014-2980    

DOI:10.1002/eji.1830270207

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractT cells belong to two separate lineages based on surface expression of αβ or γδ T cell receptors (TCR). Since during thymus development TCR β, γ, and δ genes rearrange before α genes, and γδ cells appear earlier than αβ cells, it has been assumed that αδ cells are devoid of TCR α rearrangements. We show here that this is not the case, since mature adult, but not fetal, thymic γδ cells undergo VJα rearrangements more frequently than immature αβ lineage thymic precursors. Sequence analysis shows VJα rearrangements in γδ cells to be mostly (70 %) nonproductive. Furthermore, VJα rearrangements in γδ cells are transcribed normally and, as shown by analysis of TCR β‐/‐ mice, occur independently of productive VDJβ rearrangements. These data are interpreted in the context of a model in which precursors of αβ and γδ cells differ in their ability to e

ISSN:0014-2980    

DOI:10.1002/eji.1830270208

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractUnder physiological conditions, activation of CD4+T cells by major histocom‐patibility complex (MHC) antigen complexes requires engagement of both the T cell receptor and the CD4 molecule. However, CD4 ligands binding to the CD4 molecule has also been shown to inhibit T cell proliferation and interleukin (IL)‐2 production in human CD4+T cells, in an MHC‐independent way. We have previously shown that this inhibition was associated with a diminished binding activity of the IL‐2 transcription factors NF‐AT, NF‐χB, and AP‐1. AP‐1 plays a key role in the regulation of IL‐2 transcription, and ERK and JNK activities are necessary for regulating AP‐1 at both the transcriptional and the post‐transcriptional levels. We therefore studied, in human peripheral CD4+T cells, the regulation of the activities of extracellular signal‐regulated protein kinases (ERK) and c‐Jun N‐terminal kinases (JNK) by two CD4 ligands, gpi60 the envelope glycoprotein of human immunodeficiency virus (HIV) and an anti‐CD4 monoclonal antibody (mAb). Pre‐incubation of CD4+T lymphocytes in the presence of anti‐CD4 mAb or gp160 inhibits the activation of JNK in response to phorbol 12‐myristate 13‐acetate and ionomycin. In the same conditions, phos‐phorylation and activation of ERK‐2 were also inhibited. Inhibition of both JNK and ERK‐2 activities are specific for binding of CD4 ligands to the CD4 molecule. They were not observed in CD8+T lymphocytes. These results suggest that a specific inhibition of JNK and ERK‐2 activities contributes to defective IL‐2 production

ISSN:0014-2980    

DOI:10.1002/eji.1830270209

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe outcome of the signals transduced through the B cell antigen receptor (BCR) depends both on their maturational stage and on the extent of receptor cross‐linking. It is established that the BCR‐mediated apoptosis of immature B cells represents an important mechanism for tolerance induction in the pre‐immune B cell compartment. We show here that mature germinal center (GC) B cells can re‐acquire sensitivity to BCR‐induced cell death following CD40 ligation. In contrast, neither virgin nor memory B cells become susceptible to antigen receptor‐triggered apoptosis upon CD40 stimulation, suggesting that this phenomenon may play a role in the shaping of the mature B cell repertoire in GC. Our data reveal that the death signal evoked through the BCR does not involve the Fcγ receptors, does not operate through the Fas/Fas ligand system, and can be blocked by interleukin‐4. Finally, we found that the acquisition of sensitivity to the death‐promoting effect of anti‐Ig antibodies in CD40‐stimulated GC B cell cultures correlates with the induction of a centrocytic phenotype. We propose that negative regulatory signals via the BCR may delete somatically mutated centrocytes

ISSN:0014-2980    

DOI:10.1002/eji.1830270210

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractAutoimmune‐prone MRL/lpr mice, homozygous for thelprmutation, exhibit defective apoptosis and develop generalized lymphoproliferation with the accumulation of a double‐negative (DN: CD4−CD8−) T cell population. The capacity of lpr T lymphocytes to effectuate Fas‐ and perforin‐mediated cytotoxicity was investigated. Spleen and lymph nodes cells spontaneously lyse Fas+targets (thymocytes) through a Fas‐mediated mechanism as a consequence of their overex‐pression of Fas ligand (FasL) confirmed by semiquantitative reverse transcription (RT)‐PCR and immunoprecipitation analysis. This cytotoxicity was greatly increased after stimulation of the effectors by phorbol myristate acetate (PMA)+ionomycin. Under these conditions, MRL/lpr spleen and LN cells exhibited strong Fas‐mediated Ca2+‐independent cytotoxic activity against wild‐type Fas+(H‐2 compatible or incompatible) thymocytes or lipopolysaccharide (LPS)‐transformed blast cells. Such Fas‐mediated cytotoxic activity was also observed with C57BL/6‐lpr, but never with wild‐type C57BL/6 or MLR+/+ effectors. Depletion experiments showed that the effector cells of this Fas‐mediated cytotoxicity were DN T cells. This subset, which representin vivoactivated T cells, can spontaneously lyse Fas+targets by a mechanism that does not need the interaction of the T cell receptor (TCR) with major histocompatibility complex molecule plus antigen. This lytic potential is increased by PMA+ionomycin, which sends a second activation signal to these primed T cells. Therefore, the small amounts of Fas receptor expressed on MRL/lpr tissues may account for their nonspecific autoimmune attack by DN cells. In Con A‐containing medium, which allows detection of the perforin‐mediated pathway against Fas−targets, cytotoxic CD8+effectors were detected that are able to kill lpr thymocytes via a Ca2+‐dependent pathway. Thus, in MRL/lpr mice, these CD8+cells could constitute potent cytotoxic effectors ag

ISSN:0014-2980    

DOI:10.1002/eji.1830270211

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY