摘要:

AbstractThe Fcγ receptor (R)IIIA (CD16) plays an important role in regulating the cytotoxic and non‐cytotoxic functions of human natural killer (NK) cells. Some anti‐CD 16 monoclonal antibodies (mAb) have been shown to stimulate NK activity, while human monomeric (m) IgG induces dose‐dependent inhibition of NK activity. To explore further these interactions mediated via FcγRIIIA, purified NK cells were cultured for 2–3 days in the presence of mIgG, 3G8 mAb, interleukin‐2 (IL‐2) or a combination of mIgG or 3G8 with IL‐2. Binding of mIgG or 3G8 to FcγRIIIA induced divergent effects of functions of cultured NK cells: 3G8 mAb + IL‐2 induced dose‐dependent inhibition of proliferation attributable to apoptosis; in contrast, mIgG + IL‐2 significantly increased NK cell proliferation. Incubation of NK cells in the presence of mIgG up‐regulated expression of surface activation markers (CD69, IL‐2Rα, ICAM‐1), cytotoxicity, cytokine production (IL‐1β, IFN‐γ and TNF‐α) and release of soluble IL‐2R. Thus, mIgG binding to FcγRIIIA induced stimulatory signals in human NK cells, leading to up‐regulation of IL‐2Rα expre

ISSN:0014-2980    

DOI:10.1002/eji.1830260602

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe CD40: CD40 ligand (CD40L) interaction provides T lymphocyte‐mediated help for B lymphocyte and monocyte function but has also been shown to serve as a co‐stimulus for T lymphocyte activation. In this report, we studied the regulation of CD40 expression and its functional relevance for the human dendritic cell (DC) stimulation of T lymphocytes. Only a small subpopulation of directly isolated blood DC expressed CD40. However, CD40 was rapidly up‐regulated by culture, and its expression was further enhanced by interleukin (IL)‐1α, IL‐1β, IL‐3, tumor necrosis factor‐α and granulocyte/macrophage‐colony‐stimulating factor. Expression of CD40L on DC was not detected. The proliferation of T lymphocytes in an allogeneic mixed leukocyte reaction, stimulated by blood DC or epidermal Langerhans cells, was significantly reduced in the presence of the CD40 immunoglobulin (CD40Ig) fusion protein or CD40L monoclonal antibodies. Cross‐linking of CD40 on directly isolated DC with mouse CD40L trimer (mCD40LT) markedly augmented CD80 and CD86 up‐regulation. Nevertheless, the same cross‐linking mCD40LT inhibited DC stimulated T lymphocyte proliferation. When CD40Ig was added simultaneously with CTLA‐4Ig, only minimal and variable additional inhibition of DC‐stimulated allogeneic T lymphocyte proliferation and IL‐2 secretion was observed, compared to each fusion protein alone. These results suggest that both CD80/CD86‐dependent and ‐independent components of DC‐T lymphocyte CD40: CD40L co‐stimulation exist and further emphasize that the majority of blood DC have to differentiate or be activ

ISSN:0014-2980    

DOI:10.1002/eji.1830260603

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractDuring the selection of B cells within germinal centers (GC) on the basis of their affinity for T‐dependent antigen, B cells not positively selected are eliminated within GC. This process of B cell death has been considered to be apoptosis. In a recent study, we have reported that, although a substantial number of thymocytes were considered to be dead because of their extremely small cell size and heavy chromatin condensation even though they were not yet phagocytosed (pyknosis), they were devoid of DNA fragmentation, the most characteristic feature for apoptosis. In this study, we examinedin vivothe mechanism of B cell death within GC by using the terminal deoxynucleotidyl transferase (TdT)‐mediated dUTP‐biotin nick end‐labeling (TUNEL) method to detect DNA double‐strand breaks. TUNEL+B cells were scattered throughout the upper dark and the light zones of GC. Double staining of the sections by the TUNEL method and acid phosphatase (AcP) activities showed that all the TUNEL+B cells were phagocytosed by macrophages. Light microscopic and ultrastructural studies revealed the presence of small unphagocytosed B cells within the light zone. These cells are undoubtedly dead because they were much smaller than surrounding lymphoid cells and have a heavy chromatin condensation. Furthermore, ultrastructural detection of DNA fragmentation confirmed that these small unphagocytosed B cells were TUNEL−, implying that DNA fragmentation is not primarily involved in the cell death process of these small dead B cells. These results indicate that most B cells, not positively selected and thus destined to be eliminated, die within GC without DNA fragmentation, and are subsequently phagocytosed by macrophages and become TUNEL+. Typical apoptosis, characterized by DNA fragmentationin situ, is not the predominant type of cell death that occurs during the selection of B

ISSN:0014-2980    

DOI:10.1002/eji.1830260604

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractInterleukin‐12 (IL‐12) is a key immunoregulatory cytokine which promotes cell‐mediated immunity. Its influence on the humoral immune response is less clearly defined. In this study, the effect of systemic IL‐12 treatment on the T cell‐dependent humoral immune response in the rat was examined using an experimental system in which PVG‐RT1ucongenic rats were immunized with class I Aaalloantigen in the form of a blood transfusion from the recombinant PVG.R8 rat strain. Administration of IL‐12 following allo‐immunization augmented the humoral immune response as determined by increased levels of cytotoxic anti‐class I major histocompatibility complex antibodies. However, the effect of IL‐12 on individual IgG isotypes was highly selective. Levels of allospecific antibodies of the IgG2b and IgG2c subclasses were markedly increased, whereas IgG1 alloantibody levels were profoundly reduced. The observed alterations in alloantibody response were dependent, in large part, on the stimulatory effect of IL‐12 on interferon (IFN)‐γ production by T lymphocytes and natural killer cells, since they were abrogated by co‐administration of neutralizing anti‐IFN‐γ monoclonal antibody fol

ISSN:0014-2980    

DOI:10.1002/eji.1830260605

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractInterleukin‐12 (IL‐12) is a heterodimeric cytokine composed of p35 and p40 subunits and is required for induction of T helper 1 (Th1) responses. Knowledge of how the IL‐12 gene is regulated will permit an understanding of susceptibility and resistance to pathogenic microbes and to autoiummune diseases. In this report, we provide the gene structures, nucleotide sequences and chromosomal assignment for the p35 and p40 subunits of mouse‐IL‐12. The p35 and p40 subunit genes are distributed over 8 kb and 14 kb, and map to chromosomes 3 and 11, respectively. The p35 subunit gene consists of eight exons, including a 5′‐noncoding exon that was defined by sequence comparison of genomic DNA with the 5′ends of novel cDNA molecules. Transcription of p35 mRNA can start from the first exon but can also initiate further downstream. Potential transcription regulatory elements, AP1, AP2, AP3, NF‐kB and GATA recognition sequences, are located within 523 bp upstream of the p35 gene; however, no TATA box was identified. The p40 subunit gene consists of eight exons. A TATA box is located 30 bp upstream from the transcription start site, and AP1, AP3, GATA, and Pu.1 recognition sequences are located within 690 bp upstream of the p40 gene. An AGTTTCTACTTT sequence, which acts as an interferon‐γ response element in the promoter of the major histocompatibility complex class I gene, was also found upst

ISSN:0014-2980    

DOI:10.1002/eji.1830260606

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractTyrosine phosphorylation of different substrates is the earliest intracellular signal detected after T cell receptor (TcR) ligation. Several tyrosine kinases have been detected associated to the CD3‐TcR complex in stimulated or unstimulated cells, including p56lck, p59fynand ZAP‐70. We have observed, in one mouse T helper CD4 T cell line, that most TcR‐ or CD3‐associated tyrosine kinase activity comes from CD4:p56lck(Diez‐Orejas, R., Ballester, S., Feito, M. J., Ronda, M., Ojeda, G., Criado, G., Portolées, P. and Rojo, J. M.,EMBO J.1994.13: 90). To analyze whether this is a major way of tyrosine kinase association to the TcR in normal CD4+T cells, we examined the nature and mode of association of tyrosine kinases to the TcR complex in normal spleen CD4+T lymphocytes. Our results show that, in normal CD4+T lymphocytes, as in CD4+T cell lines, there is a stable and readily detectable association between CD4: p56lckand the TcR/CD3 complex, as determined byin vitrokinase activity in immunoprecipitates from cell lysates. However, TcR/CD3 complexes from nature CD4+lymphocytes have detectable amounts of p56lckassociated in a CD4‐independent manner, as shown by immunodepletion of the lysates with anti‐CD4 antibodies. In addition, TcR/CD3 also bind p59fynregardless of the presence of CD4. Conversely, we have observed that CD4 co‐precipitates small quantities of p56fynin a TcR/CD3‐independent manner. Overall, our data suggest the existence of different possible molecular complexes between TcR/CD3, CD4 and their attending kinases, as well as some quantitative and qualitative differences between CD4+T cells and CD4+T cell lines in kinase association to t

ISSN:0014-2980    

DOI:10.1002/eji.1830260607

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe cytokines interleukin (IL)‐2 and IL‐15 share many biological activities as a consequence of their utilization of the β and γ chains of the IL‐2 receptor. However, each cytokine binds to a specific receptor α chain; IL‐2 with low affinity and IL‐15 with high affinity. Here, we demonstrate that IL‐15, like IL‐2, up‐regulates expression of IL‐2Rα on human T and B cells, but rapidly down‐regulates IL‐15 high‐affinity binding sites, which represent IL‐15Rα. This leads to a decreased responsiveness to IL‐15 as measured by induction of Jak3 tyrosine phosphorylation. These results suggest a mechanism by which IL‐15, a product of activated macrophages, may cooperate with IL‐2 at the initiation of an immune response and enhance subsequent IL‐2

ISSN:0014-2980    

DOI:10.1002/eji.1830260608

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractIntraepithelial lymphocytes have been shown to be oligoclonal and to be disseminated widely along the human intestine. However, studies using monoclonal antibodies have suggested that superimposed on the widespread clones, there is local variability in the mucosal T cell population. We have investigated the possibility that local dominant clones of T cells are present in the colonic mucosa by polymerase chain reaction (PCR) amplification of T cell receptor β chain junctional regions using DNA extracted from microdissected fragments of tissue sections. Colon from two right hemicolectomy specimens was sampled at 7‐cm intervals. Adjacent areas of mucosa were microdissected from sections from each colon sample. When the PCR products were separated according to size on polyacrylamide gels, bands of identical size were often observed when DNA extracted from adjacent fragments of mucosa had been used. Different bands were present when the different samples of colon had been studied. Sequencing of the PCR products confirmed that clonally related T cells were present in adjacent areas of mucosa, whereas different clones dominated at distant sites. DNA extracted from cells microdissected from the T cell zone of Peyer's patch was treated identically. The sequences obtained from the Peyer's patch, as expected, were diverse. However, one of the sequences identified was identical to that of one of the clones in the colon, implying that this clone was either trafficking through the Peyer's patch or possibly originated from the Peyer's patch. In this study, we also identified the Peyer's patches as a site of proliferation of CD4+T cells. No T cell division was observed in the lamina propria. The molecular and immunohistochemical observations together support the hypothesis that the Peyer's patches are a source of mucosal T cel

ISSN:0014-2980    

DOI:10.1002/eji.1830260609

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractCD22 is a B lymphocyte‐specific membrane protein that functions as an adhesion molecule via its interactions with a subset of α2‐6‐linked sialic acid‐containing glycoproteins. Engagement of CD22 with a monoclonal antibody (HB22.23) that blocks the binding of CD22 to its ligands results in rapid CD22 tyrosine phosphorylation and in increased association of CD22 with p53/561yn kinase, p85 phosphatidyl inositol‐3 kinase, and p72syk kinase. Synthetic peptides that span various regions of the intracellular portion of CD22 were used to map potential kinase binding sites. All three kinases associated with a tyrosine‐phosphorylated peptide that spans tyrosine amino acid residues 822 and 842, implicating this as an important region in mediating CD22 signal transduction. In addition, purified p56lyn directly bound to the same peptide. Engagement of CD22 with HB22.23 was sufficient to stimulate normal B cell proliferation. This study further substantiates the importance of CD22 as a B lymphocyte signaling molecule and begins to unravel the mechanisms by which CD22 cross‐linking can alter B

ISSN:0014-2980    

DOI:10.1002/eji.1830260610

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe ability of interleukin‐1 (IL‐1) to activate epidermal cell populations supports its role as a key cytokine in the pathogenesis of a number of inflammatory skin diseases. In the present study, we have examined the effect of interferon (IFN)‐γ on the expression of the IL‐β gene in mouse RAW 264.7 macrophages activated by lipopolysaccharide (LPS) plus tumor necrosis factor (TNF)‐α. Incubation of macrophages with both LPS and TNF‐α resulted in the expression of both IL‐1β and inducible nitric oxide synthase (iNOS) mRNA transcripts and increased the release of IL‐1β protein and nitrite production in culture supernatants. Addition of IFN‐γ up‐regulated the expression of the iNOS gene in cells activated by LPS + TNF‐α, but significantly suppressed the induction of IL‐1β gene expression in a dose‐dependent manner. The suppression required neitherde novoprotein synthesis nor involved destabilization of the mRNA transcripts. Together, these findings suggest that IFN‐γ can be an important regulatory cytokine in a chronic inflammatory site and may explain its purported anti‐inflammatory eff

ISSN:0014-2980    

DOI:10.1002/eji.1830260611

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY