摘要:

AbstractCD4 T cells bearing high (240–190 kDa) and low (180 kDa) molecular mass isoforms of the leukocyte common antigen CD45 define functionally distinct subsets which have been equated with naive and memory T cells. In the rat, CD4 T cells expressing a high molecular mass isoform [identified by monoclonal antibody MRC‐OX22 (anti‐CD45RC)] exchange this for the 180 kDa molecule (CD45RC−) when stimulated by antigen. Here we show, by transferring mature allotype‐marked CD45RC−CD4 T cells (depleted of immature Thy‐1+CD45RC−recent thymic emigrants) into normal euthymic recipients, that many T cells re‐express the high molecular mass isoform in less than 6 h. By 24 h, 30–60% of CD45RC−CD4 T cells became CD45RC+; within a week the entire cohort appeared to exchange the low for the high molecular mass isoform. Isoform exchange was dynamic and many CD4 T cells returned once again to the CD45RC−state. CD45RC−CD4 T cells declined in number more rapidly than the CD45RC+subset after transfer. The results suggest that CD45R isoforms distinguish between resting T cells (CD45RC+) and those which have encountered antigen in the recent past. CD45R isoforms would appear to be unsuitable markers of

ISSN:0014-2980    

DOI:10.1002/eji.1830241102

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractStatistical correlations between the expression of various HLA antigens and certain autoimmune diseases have been observed for both HLA class I and II antigens. Autoimmune diseases like spondyloarthropathies and anterior uveitis are associated with HLA‐B27, but uveitis in Behçet's disease with HLA‐B51. We describe a peptide from disease‐associated HLA class I antigens sharing sequence homologies with a highly uveitogenic epitope from the retinal autoantigen S‐antigen. S‐antigen induces autoimmune uveitis in the animal model and is a major autoantigen in human disease. The HLA peptide induced uveitis in the Lewis rat and, moreover, suppressed S‐antigen‐induced disease when administered orally. Patients' PBL cross‐reacted with the HLA‐ and corresponding retinal peptide, explaining the organ specific

ISSN:0014-2980    

DOI:10.1002/eji.1830241103

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe regulation of the cell surface expression of ICAM‐3 (CD50) was investigated in human neutrophils. Immunofluorescence flow cytometry analysis revealed a remarkable and very rapid down‐regulation of the ICAM‐3 cell surface expression upon neutrophil activation with stimulating agents such as phorbol myristate acetate (PMA) or calcium ionophore. A similar low expression of ICAM‐3 was observed on neutrophils from patients undergoing hemodialysis with cell‐activating cellulosic membranes. Internalization assays with125I‐labeled anti‐ICAM‐3 monoclonal antibody (mAb) suggested that ICAM‐3‐down‐regulation was due to antigen release from the cell surface towards the outer milieu, rather than to antigen internalization. Immunoprecipitation studies confirmed this down‐regulatory effect, and revealed the presence of ICAM‐3 in cell‐free supernatants from activated neutrophils. Furthermore, the presence of a soluble form of ICAM‐3 with a range of concentrations of 0–296 ng/ml in the plasma from healthy human volunteers was detected by using a two‐site mAb radioimmunoassay. A proteolytic mechanism likely accounts for this process since protease inhibitors virtually abrogated the PMA‐induced down‐regulation of ICAM‐3. Functional studies showed that anti‐ICAM‐3 mAb were able to trigger homotypic neutrophil aggregation both before and after ICAM‐3 down‐regulation, indicating that the fraction of ICAM‐3 molecules remaining on the neutrophil surface upon activation are still capable of sustaining cell adhesion. In contrast, the loss of L‐selectin (CD62L) on activated neutrophils was almost complete, thus leading to an impairment of L‐selectin‐mediated neutrophil‐endothelial cell adhesion. These results indicate that ICAM‐3 is released to the medium upon neutrophil stimulation and that both ICAM‐3 an

ISSN:0014-2980    

DOI:10.1002/eji.1830241104

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mechanisms of CD4 depletion and hyporesponsiveness during human immunodeficiency virus (HIV) infection are still unknown. Given the ability of superantigens to stimulate a higher number of lymphocytes than conventional antigens, they may play a major role in this process. Recently, a novel superantigen, the rabies virus nucleocapsid (NC), was described in humans. In the present work, we tested the responses of peripheral blood lymphocytes from asymptomatic HIV‐infected patients to this superantigen. In contrast to its effect in normal controls, NC failed to expand T cells from HIV‐infected individuals expressing the Vβ8 family, and induced a strong decrease in the response to CD3 activation. This absence of response was not the consequence of programmed cell death, and was explained by an anergic state induced by the superantigen. NC superantigen was also able to induce polyclonal activation of B cells, as measured by the secretion of anti‐HIV antibodies and autoantibodies. Moreover, Vβ8 depletion experiments showed that induction of autoantibody secretion was Vβ8 dependent, whereas secretion of HIV‐1 antibody was not. Interleukin secretion studies showed that NC was able to induce high levels of interleukin‐4 and interleukin‐10. Taken together, our results suggest a role for exogenous viral superantigens such as NC in the induction of T cell hyporesponsiveness and polyclonal B cell activation during HIV infection. The induction of a Th2 response and the role of these superantigens in the immunopathogenesis of acquired immunodeficiency syndrome

ISSN:0014-2980    

DOI:10.1002/eji.1830241105

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractRapid up‐regulation of the functional activity of integrin adhesion receptors is a hallmark of T cell activation. Monoclonal antibody engagement of the CD7 antigen on human T cells results in an increase in β1 and β2 integrin‐mediated adhesion within minutes. This suggests that CD7 is capable of transducing intracellular signals, and is consistent with other indirect studies implicating CD7 as a signaling receptor on T cells. In this report, we have explored the intracellular mechanism by which CD7 modulates integrin functional activity. First, CD7‐mediated up‐regulation of T cell adhesion was found to be unique when compared to phorbol ester stimulation and CD3/T cell receptor cross‐linking, based on differences in the kinetics of activation‐dependent integrin‐mediated adhesion and lack of increase in CD2 functional activity. Second, up‐regulation of integrin activity mediated by CD7 cross‐linking was completely inhibited by the tyrosine kinase inhibitor herbimycin A. Third, antiphosphotyrosine immunoblotting demonstrated that antibody engagement of CD7 results in a rapid but transient increase in tyrosine phosphorylation in human T cells. Finally, CD7 immunoprecipitates containin vitrokinase activity, as demonstrated by phosphorylation of a predominant band of 80 kDa and multiple other bands. Phosphoamino acid analysis of the 80‐kDa substrate revealed phosphorylation on tyrosine as well as serine and threonine residues. Together, our results suggest that CD7 is associated with tyrosine kinase activity and that this tyrosine kinase activity correlates with the ability of CD7 to regulate T cell integri

ISSN:0014-2980    

DOI:10.1002/eji.1830241106

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractA CD4+Vβ8.2+T cell clone specific for the peptide 72–89 of guinea pig myelin basic protein (GMBP) was used to induce acute experimental autoimmune encephalomyelitis (EAE) in Lewis rats. To assess apoptosis in inflammatory cells infiltrating the central nervous system (CNS), we extracted cells from the spinal cord, enriched them for T cells and performed flow‐cytometric analysis of their DNA stained with propidium iodide. The presence of apoptosis was confirmed by the demonstration of DNA fragmentation on gel electrophoresis. A gradual increase in the proportion of apoptotic cells was observed between 4 and 7 days after the transfer of the encephalitogenic T cells. The highest frequency of apoptotic cells (9.2 ± 1.2%) was observed 7 days after cell transfer, when clinical recovery commenced. Passive transfer of ovalbumin‐specific cells resulted in only a background level (0.8%) of apoptosis in the CNS. We conclude that the apoptotic process selectively eliminates autoreactive T cells from the CNS as: (a) there was a selective disappearance of disease‐relevant CD5+Vβ8.2+cells from the CNS during the course of EAE; (b) there was a decrease in the frequency of CNS‐infiltrating T cells reactive to the GMBP 72–89 peptide during the course of EAE, and in a standard proliferation assay there was a loss ofin vitroreactivity of CNS‐infiltrating cells to this peptide, but not to a non‐CNS antigen (ovalbumin); (c) simultaneous surface labeling and DNA analysis of CNS‐infiltrating cells revealed that the frequency of Vβ8.2+cells was about sevenfold higher in the apoptotic T cell population than in the normal (non‐apoptotic) T cell population; and (d) we were unable to detect recirculation of the Vβ8.2+cells to lymphoid organs after their frequency decreased in the CNS. The selective apoptotic elimination of autoreactive T cells from the target organ of this spontaneously resolving autoimmune disease may have implications for the understanding of the mechanism by which an autoimmune attack is terminated and for the design of therapeutic strategies to

ISSN:0014-2980    

DOI:10.1002/eji.1830241107

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe most important immunopathological consequence of experimental mycobacterial infection is the suppression of T cell‐mediated immune response to both mitogens and mycobacterial antigens. We registered that there was decreased concanavalin A‐induced spleen cell proliferation in infected susceptible BALB/c mice as compared to normal mice. In resistant (C3H/HeJ) mice, infection with the bacteria did not induce any suppression in the mitogen‐induced lymphoproliferation. Likewise, delayed‐type hypersensitivity (DTH) responses, to keyhole limpet hemocyanin and mycobacterial crude soluble antigen were suppressed in infected BALB/c mice but not in C3H/HeJ mice. This depressed T helper cell function may either be due to defective T cell‐receptor occupancy by antigen‐Ia complex or altered co‐stimulatory signals provided by antigen‐presenting cells. In the present study, we have investigated the status of certain co‐stimulatory molecules on the infected macrophages from both susceptible and resistant mice. Our results demonstrate that upon mycobacterial infection, the macrophages are rendered incapable of delivering the co‐stimulatory signals to T helper cells, possibly due to the involvement of prostaglandin, as inhibition of its biosynthesis by indomethacin reversed the defect. Furthermore, the selective regulation was bacteria‐induced as killing of the bacteria by rifampicin abrogated the derangements in the expression of co‐stimulatory molecules on theMycobacterium‐infected macrophages. Our observations revealed that upon infection withMycobacterium tuberculosis, B7 was down‐regulated while ICAM‐1 was increased only in BALB/c but not in C3H/HeJ mice. Expression of VCAM‐1 did not change during the infection in either strain of mice. We found that these changes in ICAM‐1 and B7 expression on the surface of infected macrophages resulted in inhibition of DTH‐mediating functions of T helper cells from BALB/c mice. The results obtained in this study describe not only a novel immune evasion strategy adopted byMycobacterium, but also open up the possibility of immunotherapy of mycobacterial infection by selective manip

ISSN:0014-2980    

DOI:10.1002/eji.1830241108

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractCells undergoing death by apoptosis are rapidly engulfed by phagocytesin vivo, a highly efficient process which prevents leakage of potentially dangerous intracellular contents from dying cells to neighboring tissue. We have tested a panel of monoclonal antibodies (mAb) specifying a range of human monocyte/macrophage surface antigens for their capacity to inhibit thein vitrorecognition of apoptotic cells by human peripheral blood monocyte‐derived macrophages. The results identify the antigen defined by the 61D3 mAb, a widely‐used marker of monocyte/macrophage lineage cells, as an important mediator of apoptotic cell recognition. In our system, apoptotic, but not viable, cells were recognized by the cultured macrophages and 61D3 was found to inhibit the recognition of all apoptotic cell types tested, including Ca2+ionophore‐treated or growth factor‐depleted B and T lymphocyte lines, tonsillar germinal center B cells, irradiated peripheral blood lymphocytes and senescing neutrophils. Furthermore, the apoptotic cell recognition pathway specified by 61D3 could be distinguished from that involving the macrophage αvβ3vitronectin receptor which has been shown previously to play an important role in the recognition of apoptotic cells. These results provide further evidence that the mechanisms underlying rapid clearance of apoptotic cells involve multiple phagocyte

ISSN:0014-2980    

DOI:10.1002/eji.1830241109

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractAs a preliminary step towards the use of cell surface single‐chain class I major histocompatibility complex (MHC) molecules as T cell immunogens, we have engineered a recombinant gene encoding a full‐length cell surface single‐chain version of the H‐2Ddclass I MHC molecule (SCβDdm) which has β2‐microglobulin (β2m) covalently linked to the amino terminus of a full‐length H‐2Ddheavy chain via a peptide spacer. The single‐chain protein is correctly folded and stably expressed on the surface of transfected L cells. It can present an antigenic peptide to an H‐2Dd‐restricted antigen‐specific T cell hybridoma. When expressed in peptide‐transport‐deficient cells, SCβDdm can be stabilized and pulsed for antigen presentation by incubation with extracellular peptide at 27° or 37 °C, allowing the preparation of cells with single‐chain molecules that are loaded with a single chosen antigenic peptide. SCβDdm can be stably expressed in β2m‐negative cells, showing that the single‐chain molecule uses its own β2m domain to achieve correct folding and surface expression. Furthermore, the β2m domain of SCβDdm, unlike transfected free β2m, does not rescue surface expression of endogenous class I MHC in the β2m‐negative cells. This strictcisactivity of the β2m domain of SCβDdm makes possible the investigation of class I MHC function in cells, and potentially in animals, that e

ISSN:0014-2980    

DOI:10.1002/eji.1830241110

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe reticuloendothelial system includes macrophages and endothelial cells. These cells are produced and destroyedin vivowith a precision that implies the existence of homeostatic mechanisms. The stimuli for endothelial cell proliferation and monocyte production are becoming well characterized. However, the mechanisms involved in eliminating these cells are poorly understood. One mechanism involved in cellular elimination is apoptosis, which can be triggered in some cells by ligation of the Fas molecule. In this report we have investigated whether macrophages and endothelial cells express the Fas molecule, and whether Fas transmits an apoptosis‐inducing signal in these cells. We demonstrate that macrophages express Fas and readily undergo apoptosis when cultured with anti‐Fas. In contrast, while endothelial cells can express the Fas molecule, Fas ligation is insufficient to induce apoptosis. These results suggest differential regulation of Fas function among cells of the reticuloendothelial system, and imply different mechanisms of homeosta

ISSN:0014-2980    

DOI:10.1002/eji.1830241111

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY