摘要:

AbstractThe interaction of the T cell receptor with the antigen/major histocompatibility class II complex is insufficient to induce optimal T cell activation. Co‐stimulatory signals, including those provided by CD28/CTLA‐4 on T cells and B7 molecules (B7‐1, −2 and −3) on antigen‐presenting cells, are also required. CD28‐B7 interactions can be blocked by a soluble human CTLA‐4 chimeric protein (CTLA4Ig). We tested the effect of administration of CTLA4Ig on experimental anti‐glomerular basement membrane (GBM) autoimmune glomerulonephritis in Wistar‐Kyoto rats induced by immunization with bovine GBM. The disease is characterized by development of antibody to the α3 chain of type IV collagen (Goodpasture's antigen), deposition of rat IgG in GBM, infiltration of the kidney by T cells and macrophages, severe crescent formation and renal failure leading to death in 5–6 weeks. Animals injected with human CTLA4Ig from day 0 to day 14 or to day 35 had reduced disease severity. Beneficial effects were observed even when injections were begun after the onset of glomerulonephritis on day 14. However, the rats developed antibody to the human CTLA4Ig, associated with reduction in levels of circulating CTLA4Ig. The results provide evidence for CD28/CTLA‐4 signaling in rat autoimmune glomerulonephritis, and suggest that more effective inhibition of B7‐dependent T cell activation, such as might be achieved with homologous CTLA4Ig, could be useful in the treatm

ISSN:0014-2980    

DOI:10.1002/eji.1830240602

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractRelationships between CD45 and p56Ickhave been suggested by co‐immunoprecipitation of both proteins and by dephosphorylation of the p56lckregulatory site, Tyr 505, by CD45in vitro. We investigated whether the kinase activity of p56lckis modulated in T cells triggered via CD45. We showed that incubation of Jurkat cells with a combination of two anti‐CD45 monoclonal antibodies (mAb) (MC5/2 + D3/9) induced an increase in p56lckkinase activity, while a single mAb did not. Under these conditions, p56lckunderwent two consecutive waves of activation. This was accompanied by internalization of the kinase and by a time‐dependent increased accessibility of CD45 phosphatase at the plasma membrane. Similarly, activation and internalization of p56lckwere observed using a combination of anti‐CD45 (MC5/2) and anti‐CD2(T112) mAb, suggesting that a functional complex consisting of CD45, CD2 and p56lckwas formed upon cell triggering. Taken together, these results suggests that: (i) CD45 participates in the regulation of p56lckkinase activityin vivoand that (ii) CD45 could play a mediator role in the stimulation and endocytosis of p56lckthrough the CD

ISSN:0014-2980    

DOI:10.1002/eji.1830240603

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractImmunotargeting is a novel technique whereby antigen is directed against antigen‐presenting cells (APC) by conjugation to specific monoclonal antibodies (mAb). In this study we have employed the technique to investigate the efficiency of macrophages as APC compared with constitutively major histocompatibility complex (MHC) class II‐positive cells.i.e.dendritic leukocytes and B cells.in vivo. We first studied the organ retention of the radiolabeled conjugates by gamma counting, and their distribution within the draining lymph nodes by autoradiography. We could confirm that the conjugates reached the cells at which they were aimed. We then measured primary and secondary humoral responses. The results confirmed previous findings that targeting with mAb against MHC class II,i.e.to dendritic leukocytes, strongly enhanced the primary humoral response. In contrast, anti‐IgD conjugates, directed against B cells gave only weak primary responses. Although conjugates directed against macrophages were retained for a longer time than the other conjugates, the primary humoral response was virtually abolished. The secondary responses, however, were at least as strong as those obtained in animals primed with control conjugates, whereas animals primed with anti‐MHC class II conjugates showed little if any amplification of the secondary response. The discrepancies between the various conjugates could not be ascribed to TH1versusTH2 responses as IgG1, IgG2a, IgG2b and IgE titers all co‐varied in single animals. A possible explanation for the observed results is that macrophages fail to induce cytokine production for terminal differentiation of B cells to plasma cells, whereas conversely, upon presentation by dendritic leukocytes most stimulated B cells mature to plasma cells, leaving less progeny for immunologic

ISSN:0014-2980    

DOI:10.1002/eji.1830240604

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe heterogeneous expression of lymphocyte homing receptors (HR) by the (CD45RAlow/ROhigh) memory/effector T cell population in the human is thought to define subsets with tissue‐selective recirculatory potential. To investigate further the localization characteristics of these T cells, we used multiparameter flow cytometry to quantitate T cell subsets defined by expression of the skin‐selective HR called the cutaneous lymphocyte‐associated antigen (CLA), the peripheral lymph node (PLN) HR L‐selectin, the mucosal‐associated HR α4β7‐integrin, and the mucosal‐associated adhesion molecule αeβ7‐integrin in either cutaneous or pulmonary immune effector sites and corresponding peripheral blood. Compared to peripheral blood, skin T cells were highly enriched for the CLA+/L‐selectin+/αeβ7‐integrin−memory/effector subset, whereas lung memory/effector T cells were predominantly CLA−to lowL‐selectin−, and almost half were αeβ7‐integrin+. α4β7‐integrin expressing memory/effector T cells were diminished in both skin and lung, suggesting that this HR is not a major participant in determining localization specificity in either of these sites. The characteristic pulmonary T cell HR phenotype did not significantly differ between the normal subjects and those with pulmonary inflammatory disease, and did not correlate with markers of T cell activation. Induction of a rapid up‐regulation of pulmonary inflammation via intrabronchial allergen challenge in asthmatic patients tended to decrease localization specificity, resulting in a more general importation of memory/effector subsets. Taken together, these results suggest that tissue microenvironments play a major role in determining the character of local T cell infiltrates via their ability to import and retain memory/effector subsets selectively or, more generally, depending on

ISSN:0014-2980    

DOI:10.1002/eji.1830240605

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe signal transduction events that follow the binding of lipopolysaccharide (LPS) to the macrophage cell surface are not well defined. In the current studies LPS was found to induce alterations in phosphorylation of monocyte proteins on tyrosine. Herbimycin A and genistein, inhibitors of tyrosine kinases, markedly attenuated LPS‐induced tumor necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6) protein and mRNA production. Reciprocally, the tyrosine phosphatase inhibitor sodium orthovanadate enhanced LPS‐induced production of TNF‐α. LPS induced a concentration‐dependent increase in tyrosine phosphorylation of several proteins, which paralleled and preceded the onset of LPS‐induced TNF‐α production. LPS stimulation had different but reproducible effects on three members of thesrcfamily of tyrosine kinases. Both Hck and Lyn kinase activity increased before the onset of TNF‐α production, consistent with their participation in the observed LPS‐induced tyrosine phosphoprotein accumulation. In contrast, Yes kinase activity was not affected. These observations were made at concentrations of LPS that required serum rich in LPS‐binding protein and the monocyte surface antigen CD14 for TNF‐α production. These data indicate that tyrosine kinases and phosphatases are involved in the signal transduction cascade by which LPS induces production of TNF‐α and IL‐6 by human monocytes, and suggest that Lyn and Hck are

ISSN:0014-2980    

DOI:10.1002/eji.1830240606

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractA pool of free HLA class I chains has been detected at the plasma membrane of all cells concomitantly expressing folded and assembled class I molecules. To determine the origin of these free HLA heavy chains, we have examined the biosynthesis of a single HLA class I molecule, HLA‐B27, expressed by a murine cell line (L‐B27). In L‐B27 cells, as previously shown in Epstein‐Barr virus‐transformed lymphoblastoid cell lines, a precursor/product relationship exists, early in biosynthesis, between free (HC10‐reactive) and beta‐2‐microglobulin (β2m)‐associated (W6/32‐reactive) class I heavy chains as demonstrated by pulse/chase experiments. At later stages in class I biosynthesis, both HC10‐ and W6/32‐reactive heavy chains display complex oligosaccharides and accumulate at the cell surface. HC10‐ and W6/32‐reactive molecules are both very stable at the cell surface, with half‐lifes (t1/2) of>7 h and ∼ 4 h, respectively. Interestingly, cell surface expression and turnover of HC10‐ and W6/32‐reactive molecules were affected by the addition of peptide ligands to the culture media. Culturing cells in the presence of HLA‐B27 ligands resulted in the increased expression of W6/32‐reactive molecules and the decreased expression of HC10‐reactive molecules. Moreover, addition of exogenous peptide extended the t1/2of W6/32‐reactive molecules to>7 h and reduced that of HC10‐reactive molecules to 4 h. These results indicate that surface HC10‐reactive molecules result largely from W6/32‐reactive molecules following peptide and β2m dissociation. Therefore, HC10‐reactive species are not only the precurs

ISSN:0014-2980    

DOI:10.1002/eji.1830240607

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractTransforming growth factor‐β (TGFβ) is a potent immunosuppressive cytokine which inhibits the antigen (Ag)‐dependent expansion of T cells bothin vitroandin vivoby mechanisms not well defined yet. Here we report that exposure of interleukin (IL)‐2‐dependent T cell lines to TGFβ2results in apoptosis defined by morphology, nucleosomal size DNA fragmentation andin situDNA end labeling. TGFβ2‐induced T cell apoptosis showed the following characteristics: (1) in contrast to the rapid evolution of apoptosis following IL‐2 deprivation, apoptosis of T cells triggered by TGFβ2was delayed; (2) cycloheximide prevented TGFβ2‐induced apoptosis of CTLL‐2 but not of OVA‐7 T helper cells; (3) in contrast to apoptosis following IL‐2 deprivation, TGFβ2‐mediated T cell apoptosis was not associated with decreased expression of the proto‐oncogenes,bcl‐2 or c‐myc; (4) TGFβ2‐induced apoptosis was not restricted to IL‐2‐dependent T cell lines since the IL‐4‐dependent T cell line, CT.4S, as well as EL4 lymphoma cells, which grow independently of exogenous IL‐2, were also susceptible to TGFβ2‐mediated apoptosis. Taken together, these data may present a novel mechanism of TGFβ2‐mediated suppression of T cell expansion in response to Ag and IL‐2, the activation of the endogenous death program of apoptosis, which appears to operate independently of direct

ISSN:0014-2980    

DOI:10.1002/eji.1830240608

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractTo study the biological consequences of cytokine production and apoptosis by intraepithelial lymphocytes (IEL), we have studied these characteristics in both the high and low density CD3+IEL populations. Stimulation of low‐ or high‐density CD3+IEL via the T cell receptor (TCR)‐CD3 complex using monoclonal anti‐CD3, anti‐αβ TCR or anti‐γδ TCR antibodies resulted in opposing effects. In one case, a significant number of the high‐density CD3+T cells entered cell cycle from the resting stage (DNA replication was observed) and anti‐TCR‐CD3 treatment enhanced the numbers of interferon‐γ and interleukin‐5 spot‐forming cells in this cell fraction. In contrast, when the low‐density αβ TCR+or γδ TCR+T cells were activated via the TCR‐CD3 complex, DNA fragmentation was observed. These results demonstrated that the activation signals transduced via the TCR‐CD3 complex resulted in their entry into the cell cycle and subsequent interferon‐γ and interleukin‐5 production in the high‐density IEL T cell subset. However, identical signals induced apoptosis in the ma

ISSN:0014-2980    

DOI:10.1002/eji.1830240609

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractMolecular analysis of circular excision products and composite genomic switch regions has demonstrated that in mice, immunoglobulin (Ig) isotype switching from IgM to IgE often proceeds sequentially via IgG1. Based on analysis of Ig production in cell cultures, it has been suggested that human B cells may switch to IgE via IgG4, whereas limited molecular data fromin vitroswitched B cells suggest a direct IgM to IgE switch program. To obtain a quantitative assessment of directversussequential IgE switching in humans, we have analyzed the nucleotide sequences of 29 composite Sμ/Sϵ switch regions from freshly isolated human B lymphocytes from patients with atopic dermatitis and from B lymphocytes induced to switch to IgE synthesisin vitro.The data show that in these B cells IgE isotype switching progressed directly from IgM to IgE. We conclude that, in contrast to the murine IgM/IgE switch program, the IgM to IgE switch in B lymphocytes from patients with atopic dermatitis as well asin vitrostimulated B cells from healthy donors preferentially proceeds via direct Sμ to Sϵ switch recombinat

ISSN:0014-2980    

DOI:10.1002/eji.1830240610

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe present investigation explored age‐related alterations in T cell populations mediating allospecific responsesin vivo.Healthy aged and young H‐2band H‐2bxH‐2kmice were engrafted with major histocompatibility complex (MHC) class II‐disparate bm12 skin, rejection of which requires CD4+T cells, and MHC class I‐disparate bm1 skin, rejection of which requires CD8+T cells. Aged mice of both genders exhibited prolonged survival of bm12 skin grafts relative to their young counterparts but rejected bm1 skin grafts at a rate equivalent to that of young mice. Consistent with prolonged survival of bm12 skin grafts, markedly diminished levels of Iabm12CTL activity were elicited from T cells of aged micein vitro.However, no such decline was observed in the level of Kbm1CTL from T cells of aged mice. The alterations in Iabm12allospecific responses were not attributable to quantitative changes in CD4+T cells of aged mice, and addition of soluble T cell helper factors to response cultures of aged mice did not augment Iabm12cytotoxic T lymphocytes activity. These data demonstrate that aging fundamentally affects CD4+T cell‐mediated allospecific responses particularlyin vivo, and that deficient generation of soluble T cell helper factors alone cannot explain

ISSN:0014-2980    

DOI:10.1002/eji.1830240611

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY