摘要:

AbstractHere we describe a novel “antibody‐redirected cell adhesion” (ARCA) assay. This assay measures heterotypic cell‐cell adhesion, resulting from antibody bridging between Fcγ receptors type II (CD32) on leukocytes, and clustered intergrins on adherent cell monolayers. This ARCA activity, facilitated by integrins αβ1or α4β1, required an intact cytoskeleton, but did not involve typical integrin ligand binding sites or divalent cations. Furthermore, deletion of the α4cytoplasmic tail almost completely abrogated integrin ARCA activity, suggesting an alteration of integrin recruitment into adhesive sites. If two or more tail residues were present after the conserved GFFKR motif, then ARCA activity was largely restored. Although α4tail deletion caused loss of ARCA activity, it had no effect on the binding of VCAM‐1 to intact α4‐transfected K562 cells. In conclusion, the integrin α chain tail can positively regulate integrin‐dependent cell adhesion by a receptor recruitment/clustering mechanism independent of conventional integrin ligand

ISSN:0014-2980    

DOI:10.1002/eji.1830270112

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe mechanism leading to selective production and accumulation of eosinophils in certain allergic skin diseases is unknown. Cyclophosphamide treatment (150 mg/kg) of BALB/c mice 48 h before sensitization with picryl chloride (PCI) resulted in striking blood and tissue eosinophilia, maximal at 13 days. Blood eosinophilia was not induced by the sensitization with oxazolone and 2, 4‐dinitrofluorobenzene. Challenge with 1% PCI, but not croton oil caused preferential eosinophil accumulation into the dermis, which was associated with the enhanced expression of vascular cell adhesion molecule 1 (VCAM‐1) on endothelial cells. Intraveneous administration of anti‐VCAM‐1 monoclonal antibody abrogated eosinophil infiltration. In this murine model, we examined the role of several cytokines, including chemokines in inducing selective tissue eosinophiliain vivo.Local administration of antibodies against interleukin (IL)‐1β, IL‐4, tumor necrosis factor (TNF)‐α, and RANTES, but not against IL‐5 before challenge inhibited hapten‐induced eosinophil recruitment. Intradermal injection of recombinant (r)IL‐1β, rIL‐4, rTNF‐α, rRANTES, and rMIP‐1α induced marked eosinophil accumulation. Nonetheless, intradermal rIL‐5 was not a chemoattractant for eosinophilsin vivo.Our findings suggest that IL‐1β, IL‐4, TNF‐α, and RANTES contribute to the selective accumulation of eosinophils in contact sensitivity reaction. Although circulating IL‐5 can activate eosinophils and prolong their survival, locally secreted IL‐5 is not crucial for i

ISSN:0014-2980    

DOI:10.1002/eji.1830270113

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe superantigens staphylococcal enterotoxin A and E (SEA and SEE) both contact major histocompatibility complex (MHC) class II molecules on two sites located on the α and β chains. We have investigated the role of the T cell receptor (TCR) α chain in the modulation of the various topologies of TCR/SEA (or SEE)/class II complexes. For this purpose, we have used three mouse Vβ20 T cell lines expressing different Vα domains and two T cell hybridomas expressing mouse Vβ1 or Vβ11 segments. The response of these T cells to SEA and SEE was studied in the context of presentation by wild‐type human MHC class II molecules; or by mutants on MHC, in each of the two superantigen binding sites (position α39K and β81H) to which the superantigens can still bind but with an altered conformation. Although Vβ20 T cell lines are efficiently stimulated using SEA and SEE presented by wild‐type HLA‐DR1 molecules, our results show that the nature of the TCR Vα domain can affect differently the recognition of the toxins bound to mutant class II molecules. This suggests that various functional topologies exist for both SEA and SEE/class II complexes and that the T cell response to each of these complexes can be modulated by the Vα domain of the TCR. Interestingly, the recognition of SEA and SEE is achieved in different fashions by a given

ISSN:0014-2980    

DOI:10.1002/eji.1830270114

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractInterleukin‐7 (IL‐7) receptor α chain‐deficient (IL‐7Rα‐/‐) mice have severely depleted lymphocyte populations and thymocyte development is arrested at the double‐negative (DN) stage. We show that thymocyte development in these mice can be reconstituted by the introduction of a transgenic T cell receptor (TCR), implying that one function of the IL‐7Rα chain is to initiate TCR gene rearrangement. Expression of the recombinase‐activating genesRAG1andRAG2was greatly reduced in the IL‐7Rα‐/‐thymuses, and in DN thymocytes from the TCR transgenic IL‐7Rα‐/‐mice, but was restored in double‐positive thymocytes from the TCR transgenic IL‐7Rα‐/‐mice. These data suggest that the IL‐7Rα chain controls RAG expression and initiation of TCRβ chain VDJ rearrangement in DN cells. In contrast, once cells have progressed beyond the DN stage of development the IL‐7Rα ch

ISSN:0014-2980    

DOI:10.1002/eji.1830270115

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThree monoclonal antibodies (mAb; SC‐6, SC‐12, and SC‐29) reactive with the γδ T cell‐restricted antigen WC1 were obtained immunizing mice with an ovine interleukin (IL)‐2‐dependent γδ T cell line. These mAb strongly inhibited DNA synthesis in IL‐2‐dependent γδ T cell lines with cell cycle arrest in G0/G1 phase, but did not induce apoptosis. The mAb‐induced growth arrest was reversible, either by removing the mAb or by co‐culture with mitogen or anti‐CD3 in the presence of IL‐2. In contrast, addition of phorbol ester, ionomycin and IL‐2 had no effect on the mAb‐induced growth arrest. The observations define a biologically important role for the cell surface molecule WC1 in the regulation of γδ T cell proliferation and also provide a suitable system to study the

ISSN:0014-2980    

DOI:10.1002/eji.1830270116

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractInterferon‐γ (IFN‐γ)‐inducible protein‐10 (IP‐10), a member of the C‐X‐C sub‐family of chemokines, is known to be produced by monocytes, lymphocytes, keratinocytes and endothelial cells in response to IFN‐γ Here, we show that human polymorphonuclear neutrophils (PMN) also have the ability to produce IP‐10. IFN‐γ alone had a modest effect on IP‐10 mRNA accumulation, whereas tumor necrosis factor‐α (TNF‐α), yeast particles opsonized with IgG (Y‐IgG), lipopolysaccharide (LPS), and formyl‐methionyl‐leucyl‐phenylalanine (fMLP) all failed to up‐regulate IP‐10 gene expression. However, stimulation of neutrophils with IFN‐γ in combination with either TNF‐α or LPS (but not with Y‐IgG or fMLP) resulted in a considerable induction of IP‐10 mRNA transcripts, as well as in the extracellular release of the protein. In contrast, the best inducer of IP‐10 release from peripheral blood mononuclear cells was IFN‐γ alone. Furthermore, mRNA stabilization analyses demonstrated that IP‐10 mRNA isolated from PMN stimulated with IFN‐γ only, or with IFN‐γ plus either TNF‐α or LPS, had similar half‐lives. Finally, we found that interleukin‐10, a known inhibitor of chemokine production in PMN, moderatley suppressed the extracellular production of IP‐10 in neutrophils stimulated with IFN‐γ plus either LPS or TNF‐α. Since IP‐10 is a potent chemoattractant for activated T lymphocytes, the ability of neutrophils to produce

ISSN:0014-2980    

DOI:10.1002/eji.1830270117

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThis study investigates the effect of interleukin (IL)‐4 mutant proteins and a monoclonal antibody to the IL‐4 receptor α chain on IL‐4 and IL‐13 response by B cells from X‐linked severe combined immunodeficiency (X‐SCID) patients in which the common γ chain (γc chain) gene mutations have been fully characterized and no γc chain expression was detected. In this γc chain gene knockout model, it was confirmed that the γc chain is essential for B cell responses to IL‐2 but not for IL‐4 or IL‐13. Dose‐response curves for X‐SCID and normal B cell responses to IL‐4 were indistinguishable, showing that the loss of the γc chain did not diminish the sensitivity of B cells to IL‐4. The mutant protein IL‐4Y124Dand an antibody to the IL‐4R α chain both inhibited responses of X‐SCID B cells to IL‐4 and IL‐13, showing that X‐SCID B cell responses to these cytokines are mediated by a receptor complex that includes the IL‐4R α chain but not the γc chain. Another mutant protein, IL‐4R88D, which has greatly reduced affinity for IL‐4Rα, was found to inhibit responses by normal B cells to IL‐4 but not to IL‐13. IL‐4R88Ddid not, however, inhibit X‐SCID B cell responses to IL‐4. This result is consistent with IL‐4R88Dinhibition of responses mediated by receptor complexes that include the γc chain. We propose that X‐SCID B cells responses to IL‐4 are mediated by an IL‐13 receptor complex comprised of the IL‐4R α chain associated with the recently cloned IL‐13R binding protein. This

ISSN:0014-2980    

DOI:10.1002/eji.1830270118

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractCD21 (complement receptor 2, CR2) binds the C3 degradation products, iC3b and C3d, which are covalently linked to antigen or immune complexes in the process of complement activation. The ability of antigen‐nonspecific B cells to present immune complexes containing high titers of acquired antibodies was tested. Influenza virus was incubated with serum from immune donors to create complement‐containing complexes. These bound specifically to CD21 on transfected fibroblasts and B cell lines, as measured by microcytofluorimetry. Binding of immune complexes was ablated by inactivation of serum complement. In addition, the immunoglobulin in immune human serum blocked influenza binding to cells in the absence of complement, implying a minimal role for immunoglobulin‐Fc receptor interactions in this system. Significant immune complex binding required a threshold level of CD21 expression, suggesting that only those cells with the highest levels of CD21 are likely to participate in the processing of macromolecular antigens. B cells pulsed with complement‐influenza complexes elicited an augmented response from a panel of influenza‐specific, class II‐restricted T cell clones, as compared with those which had bound immunoglobulin‐influenza complexes lacking complement. This enhanced response did not require CD35. In addition, B cell lines expressing higher levels of CD21 were more efficient in processing antigen than those with lower levels. These findings suggest that presentation of antigen by B cells in immune individuals is dependent on the binding of complement‐antigen immune co

ISSN:0014-2980    

DOI:10.1002/eji.1830270119

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractImmunoglobulin isotype switching to IgE in patients infected withSchistosoma mansoniand patients with atopic dermatitis was studied. Patients with parasitic infections or allergic diseases have a higher production of IgE. We found a fourfold increased production of Iε RNA in both patient groups as compared to control donors. The increased expression of germ‐line transcripts correlates with higher serum IgE levels. Nested primer polymerase chain reaction was used to generate Sμ/Sε fragments from DNA of patient peripheral blood mononuclear cells. Twenty‐nine out of fourty sequenced switch fragments had undergone direct joining from Sμ to ε whereas seven fragments showed mono sequential switching from Sμ via either Sμ, Sγ2, Sγ4 or Sε to Sε and four fragments demonstrated double sequential switch: Sμ/Sμ/Sγ1/Sε, Sμ/Sγ2/Sε/Sε or Sμ/Sγ1/Sγ2/Sε. The sequential switching had occurred either via deletions or inversions. Mapping of the breakpoints showed hot spots for recombination within Sμ, Sγ1 and Sε. To our knowledge, this is the firstin vivostudy in humans demonstrating that switching to IgE can occur from sequential re

ISSN:0014-2980    

DOI:10.1002/eji.1830270120

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe thymic architecture is normally compartmentalized into a central medulla surrounded by a peripheral cortical region. We investigated how compartmentalization of the thymic stroma is regulated using T cell receptor (TCR)‐transgenic mouse models. Our studies show that the signals generated by TCR/peptide/major histocompatibility complex interactions regulate thymic stromal cell compartmentalization. In TCR‐transgenic mice, normal stromal cell compartmentalization occurs when the transgenic TCR is expressed on a background that does not result in skewing toward either positive or negative selection. In models representing strong positive selection, the thymic stromal elements do not fully organize into a central medulla. Instead, small medullary foci are dispersed throughout the thymus with some regions residing directly under the capsule. The highest degree of disorganization in medullary epithelial regions is observed in TCR‐transgenic mice that exhibit negative selection. Although the medullary foci lack central organization, the expression in these regions of CD80, CD86 and CD40, as well as the clustering of dendritic cells, is similar to that observed in medullae of wild‐type mice. Thus, the organization of the medulla appears to occur in two stages: (1) small medullary epithelial regions that are dispersed in fetal thymi expand and associate with antigen‐presenting cells, and (2) the expanded medullary foci organize into a central medullary compartment. Our data suggest a model in which this second stage of stromal cell organization is increasingly inhibited as the normal balance of TCR‐mediated signals is skewed by higher‐avidity interactions between thymocytes and antigen‐p

ISSN:0014-2980    

DOI:10.1002/eji.1830270121

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY