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At least 487 records · Page 27Linked to original sources
PubMed1997

Intracerebral injection of myelin basic protein (MBP) induces inflammation in brain and causes paraplegia in MBP-sensitized B6 mice.

Brain inflammation and paraplegia can be induced by an additional intraperitoneal (i.p.) and intracerebral (i.c.) restimulation in B6 mice after standard immunization with MBP in Freund's complete adjuvant (FCA) and Bordetella pertussis coadjuvant. Only the combination of i.p. MBP/FCA and i.c. MBP injection could induce clinical paraplegia; either one alone was not effective. Clinical symptoms would develop 2 days after the i.c. injection. The induction of paraplegia was MBP-specific, as irrelevant bovine serum albumin with the same protocol could not induce it. The i.p. restimulation was requisite and needed the MBP in FCA, as MBP in PBS was ineffective. Histopathological observation manifested cellular infiltration by leucocytes in perivascular spaces and cerebral cortex. Neutrophils were prominent at 12 h after i.c. injection, then were replaced by mononuclear cells 24 h later. There were dynamic changes in cell number and immunophenotype of VLA-4+ expression in cervical lymph node cells after i.c. injection. The cells derived from cervical lymph nodes had higher MBP-stimulated proliferation than that of distal lymph nodes. This additional i.p. and i.c. stimulation provides a new manipulation to study brain inflammation.

Animals↗
PubMed1998

Effects of monoclonal antibodies to adhesion molecules on eosinophilic myocarditis in Toxocara canis-infected CBA/J mice.

Eosinophilic myocarditis followed by fibrosis of the cardiac muscle was observed in addition to peripheral blood eosinophilia in CBA/J mice infected with Toxocara canis. The infected mice were used as an experimental model of eosinophilic endomyocarditis associated with hypereosinophilic syndrome. Effects of in vivo treatment with MoAbs to adhesion molecules on eosinophilic myocarditis were examined using this experimental model. Expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells of capillaries in myocardium were increased 1 and 2 weeks after infection. Infiltration of very late antigen (VLA)-4+ and/or CD11a+ cells into the cardiac muscles was also observed 1 and 2 weeks after infection. Infiltration of eosinophils into the heart was significantly suppressed by anti-CD18 MoAb and anti-VLA-4 MoAb, and focal fibrosis of the cardiac muscle was also significantly suppressed by combined administration of anti-CD18 and anti-ICAM-1 MoAbs. These results indicate that adhesion molecules may play important roles in eosinophilic myocarditis, and that blockade of interaction between adhesion molecules and their ligands may help to control it.

Animals↗
PubMed1998

The low molecular weight Dextran 40 inhibits the adhesion of T lymphocytes to endothelial cells.

Dextrans are complex colloidal macromolecules widely used as haemorrheologic substances and anti-thrombotic agents. Here we describe a novel function of Dextran 40 by demonstrating an inhibition of T lymphocyte adhesion to endothelial cells (EC). We applied an established microassay in which constitutive and tumour necrosis factor-alpha (TNF-alpha)-induced binding of mouse T lymphoma cells (TK-1) to mouse endothelioma (eEND.2) cells is mediated by the interaction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on EC with their counter-receptors the LFA-1 heterodimer (CD11a/CD18) and VLA-4 on T cells. Dextran 40 in therapeutically achievable levels (2-32 mg/ml) reduced both constitutive and TNF-alpha-stimulated TK-1 adhesion to eEND.2. Selective preincubation of eEND.2 or TK-1 revealed that Dextran 40 acted exclusively on the T cells. To explore further the mechanisms by which Dextran 40 interfered with TK-1 adhesion, their LFA-1 and VLA-4 expression was analysed by FACS. The surface expression levels of neither receptor were affected by Dextran 40. However, confocal microscopy revealed that Dextran 40 interfered with the activation-dependent capping and clustering of LFA-1 and VLA-4 on the surface of TK-1. We conclude that Dextran 40 inhibits the capacity of TK-1 T cells to adhere to eEND.2 endothelial cells and thus may be useful for therapeutic intervention in diseases associated with enhanced T lymphocyte binding to microvascular endothelium.

Animals↗
PubMed1999

Integrin mediated adhesion of mononuclear cells from patients with familial hypercholesterolemia.

BACKGROUND: Low-density lipoproteins (LDL) can induce the adhesion of monocytes to endothelial cells. Monocytes of patients with familial hypercholesterolemia (FH) are exposed to high concentrations of LDL, and it has been reported that adhesiveness of these cells in hypercholesterolemic patients is enhanced. We investigated whether LFA-1 or VLA-4 mediated adhesion is altered in FH patients and whether HMG-CoA reductase inhibitors influence this adhesion. PATIENTS AND METHODS: LFA-1 and VLA-4 mediated adhesion to ICAM-1 and VCAM-1 coated beads was investigated using freshly isolated monocytes and T-lymphocytes from patients with homozygous FH, heterozygous FH (before and after cholesterol lowering treatment), and from controls. In addition, the expression of beta1- and beta2-integrins on these cells was determined. RESULTS: Both LFA-1 and VLA-4 mediated adhesion and integrin expression of monocytes and CD3+ cells from patients with homozygous FH and heterozygous FH was similar to that of monocytes from a control population. Treatment with HMG-CoA reductase inhibitors did not affect the adherence to ICAM-1 or VCAM-1, and did not influence the expression of integrins. CONCLUSIONS: In contrast to studies by others, we demonstrated in the present study that the actual LFA-1 and VLA-4 mediated adhesion of T-lymphocytes and monocytes is not altered in patients with FH.

Adolescent↗
PubMed1996

Treatment of established adjuvant arthritis in rats with monoclonal antibody to CD18 and very late activation antigen-4 integrins suppresses neutrophil and T-lymphocyte migration to the joints and improves clinical disease.

The migration of leucocytes from blood into the joint is a key feature of human and experimental arthritis. Adhesion molecules on leucocytes and vascular endothelium are important in this process and may be therapeutic targets for intervention in arthritis. We investigated whether monoclonal antibody treatment to block the alpha 4 integrin, very late activation antigen-4 (VLA-4), and beta 2 integrins (CD11/CD18) administered to rats during the preclinical (day 5) or clinical phase (day 10+) would modify disease. When treatment was initiated 5 days after induction of disease, development of arthritis was significantly reduced by either anti-alpha 4 (TA-2) or anti-beta 2 (WT.3) monoclonal antibodies (mAb) and the combination of both mAb was even more effective (clinical scores: control 11.4; anti-alpha 4 6.6; anti-beta 2 6.8; anti-alpha 4 + anti-beta 2 3.9). When treatment was delayed until arthritis was apparent (day 10), the anti-alpha 4 + anti-beta 2 mAb combination still significantly diminished the arthritis score on day 14 (control 13; anti-alpha 4 + anti-beta 2 7.9). Treatment with anti-alpha 4 + anti-beta 2 mAb decreased the migration to the joints of blood polymorphonuclear leucocytes (PMNL) by 66-79% and of spleen T lymphocytes by 56-75%, depending on the joint. In contrast, PMNL migration was abolished (> 98%) and T-cell migration markedly (87%) inhibited to dermal inflammatory reactions in the same animals. These findings demonstrate: that blocking mAb to alpha 4 and beta 2 integrins can reduce the severity of adjuvant arthritis, even after joint inflammation has developed; that this treatment can markedly inhibit PMNL and T-lymphocyte migration to the joints; and that yet to be defined mechanisms distinct from alpha 4 (CD49d) and beta 2 (CD11/CD18) integrins, also contribute to leucocyte migration to inflamed joints. Identifying these additional adhesion mechanisms may be required to control joint inflammation further.

Animals↗
PubMed1996

Expression and function of alpha 4/beta 7 integrin on human natural killer cells.

In this report we have analysed the expression and function of the alpha 4/beta 7 heterodimer in human natural killer (NK) cells. The expression of alpha 4 beta 7 is induced in NK cells upon activation as the anti alpha 4 beta 2 ACT-1 monoclonal antibody (mAb) family stained a minority of peripheral blood NK cells, whereas it strongly reacted with in vitro long-term interleukin-2 (IL-2)-activated NK cells. Incubation with ACT-1 on its F(ab) fragments induced a strong homotypic adhesion of NK cells, comparable to than stimulated by the anti-alpha 4 HPI 7 mAb. Cell cell interaction induced by the ACT-1 mAb was only prevented by another anti-alpha 4 mAb (HP2.1) that recognizes a different epitope. In alpha 4 beta 7-mediated cell aggregation the alpha 4 beta 7 heterodimer was redistributed to intercellular contact sites thus, suggesting a direct involvement of this integrin in the formation of cell clusters. In NK cells attached to Fibronectin (FN38) or vascular cell adhesion molecule-1 (VCAM-1), both alpha 4 beta 7 and alpha 4 beta 7 integrins were redistributed at the ventral cellular membrane forming discrete contact sites. The ACT-1 mAb only partially blocked NK cell binding to FN38, but in combination with the anti-beta 7 mAb LIAI 2, NK cell binding to FN38 was completely inhibited. In contrast. ACT-1 did not modify NK cell adhesion to VCAM-1 thus supporting the theory that the alpha 4 beta 7 binding sites for both ligands appear to be different. Our results indicate that upon IL-2-activation, expression of functional alpha 4 beta-integrin is induced on NK cells potentially participating in their interaction with both extracellular matrix and endothelial cells.

Cell Adhesion↗
PubMed1996

Integrin alpha 4 beta 7 mediates human eosinophil interaction with MAdCAM-1, VCAM-1 and fibronectin.

We have investigated the contribution of integrin alpha 4 beta 7 to human peripheral blood eosinophil adhesive interactions. Immunofluorescence and flow cytometry demonstrated constitutive expression of alpha 4 beta 7 by eosinophils. Expression of alpha 4 beta 7 or alpha 4 beta 7 was not enhanced by eosinophil activation with platelet-activating factor (PAF). Expression of alpha 4 beta 7 was confirmed by immuno-precipitation of 125I-labeled lysates analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE). Approximately 20% of unstimulated eosinophils were adherent to L1-2 cells transfected with vascular cell adhesion molecule-1 (VCAM-1) cDNA, while very few resting eosinophils adhered to mouse mucosal adressin cell adhesion molecule-1 (MAdCAM-1) transfectants. Binding of unstimulated eosinophils to VCAM-1 transfectant was inhibited by HPI 2 (an antibody that blocks both alpha 4 beta 1 and alpha 4 beta 7 functions), but not Act-1, and alpha 4 beta 1 monoclonal antibody (mAb). PAF stimulation resulted in increased binding of eosinophils to MAdCAM-1 transfectants, which was inhibited by both HPI 2 and Act-1. In contrast, PAF did not enhance binding to VCAM 1 transfectants, although binding of PAE-stimulated eosinophils to VCAM-1 could be partially inhibited by Act-1. Stimulation of eosinophils with the beta 7-activating mAb TS2 16 resulted in enhanced binding of eosinophils to both VCAM-1 and MAdCAM-1 transfectants. The increased binding was largely alpha 4 beta 7-dependent. Unstimulated eosinophils bound to soluble recombinant human (rh) VCAM-1 and fibronectin (Fn), coated on 96-well plates in dose-dependent manner. Binding was inhibited by HPI-2 and 4b4, an anti-beta 1 mAb, but not by Act-1. TS2 16 treatment increased adherent cell numbers and this enhanced binding was inhibited by Act-1. We have therefore confirmed that alpha 4 beta 7 is functionally active on unstimulated eosinophils. In contrast, PAF-induced enhancement of eosinophils binding to VCAM-1 or MAdCAM-1 was alpha 4 beta 7-dependent. In addition treatment with TS2 16 resulted in a alpha 4 beta 7-dependent enhancement of eosinophil binding to VCAM-1, MAdCAM-1 and Fn. We therefore hypothesize that alpha 4 beta 7 may have an important role in eosinophil localization in diseases such as asthma and inflammatory bowel disease.

Cell Adhesion↗
PubMed1996

Expression of VCAM-1 and VLA-4 dependent T-lymphocyte adhesion to dermal fibroblasts stimulated with proinflammatory cytokines.

In chronic inflammatory conditions, mononuclear cells infiltrate the involved connective tissue and may persist, perhaps because of binding to adhesion molecules on connective tissue cells, as well as extracellular matrix. Here we investigated whether vascular cell adhesion molecule-1 (VCAM-1) may be induced on human dermal fibroblasts by proinflammatory cytokines. Expression of VCAM-1 was determined by Northern blotting, cell enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Only trace amounts of VCAM-1 mRNA or protein were constitutively expressed on dermal fibroblasts but both were rapidly (within 4 hr) upregulated by tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha) and somewhat slower (20 hr) by interferon-gamma (IFN-gamma). The combination of TNF-alpha and IFN-gamma had at least an additive effect. The adhesion function of the expressed VCAM-1 was examined by studying the adhesion of the Jurkat T lymphocytes to fibroblasts. Adhesion of Jurkat cells to dermal fibroblasts was markedly increased by stimulation of fibroblasts with TNF-alpha and IFN-gamma (22% of cells adhered versus 9% on unstimulated fibroblasts). The increased adhesion was inhibited to that on unstimulated fibroblasts by monoclonal antibody (mAb) to domain 1 of VCAM-1, but not by mAb to domain 4. MAb to very late antigen-4 (VLA-4), the integrin counter-receptor on lymphocytes for VCAM-1, completely inhibited the increase in Jurkat cell adhesion to activated fibroblasts and partly also inhibited basal adhesion to unstimulated fibroblasts. These results suggest that VCAM-1 expression by dermal fibroblasts is inducible at the mRNA, protein and functional levels by proinflammatory cytokines. The VLA-4/VCAM-1 pathway maybe involved in adhesive interactions between T lymphocytes and activated fibroblasts in the skin during chronic dermal inflammatory conditions.

Blotting, Northern↗
PubMed1998

The role of ICAM-1/LFA-1 and VCAM-1/VLA-4 interactions on T helper 2 cytokine production by lung T cells of Toxocara canis-infected mice.

In order to study the effect of costimulatory signals on T helper type 2 (Th2) cytokine production, monoclonal antibodies (mAb) against cell adhesion molecules (CAM) were added to cells in culture obtained from the lungs of Toxocara canis (Tc)-infected mice followed by the determination of interleukin-5 (IL-5) and IL-4 in the supernatants of the culture. ES-stimulated IL-5 production in the supernatant of total lung cells was reduced by 25% when anti-intercellular adhesion molecule-1 (anti-ICAM-1) mAb, anti-CD11a mAb, or both anti-ICAM-1 and anti-CD11a mAb together were added to the culture. The addition of anti-CD18 mAb had no effects. Anti-vascular cell adhesion molecule-1 (anti-VCAM-1) mAb addition also reduced IL-5 production by 60%, although the addition of anti-very late activation antigen-4 (anti-VLA-4) mAb or both anti-VCAM-1 and anti-VLA-4 mAb together were less effective. In the case of anti-CD3 mAb stimulation, similar effects of mAb to CAM were observed. In contrast, IL-4 production induced by anti-CD3 mAb was reduced more markedly by the addition of either anti-ICAM-1 or anti-CD11a mAb than the combination of anti-VCAM-1 and anti-VLA-4 mAb. Similar effects of mAb to CAM were observed on the production of IL-5 and IL-4 by CD4+ T cells purified using a fluorescence-activated cell sorter. Coincubation with adherent cells was necessary for the significant production of IL-5 and IL-4 by CD4+ T cells. These results suggest that the VCAM-1/VLA-4 interaction is more important for IL-5 production by CD4+ T cells in the lungs of Tc-infected mice, and that the ICAM-1/lymphocyte function-associated antigen-1 interaction is more important for the production of IL-4.

Animals↗
PubMed1998

Enhancement of activation-induced cell death by fibronectin in murine CD4+ CD8+ thymocytes.

Development of T cells in the thymus is achieved through the interactions of thymocytes with their microenvironments. This study focused on the function of fibronectin (FN), a major extracellular matrix molecule in the thymus, in the cell death induced by activation via the T-cell antigen receptor. FN alone did not increase cell death in murine thymocytes above the baseline level, but it significantly enhanced the cell death induced by fixed anti-CD3 monoclonal antibody (mAb), especially when a high concentration of anti-CD3 mAb was used. DNA fragmentation increased in parallel with cell death, indicating that cell death was a result of the apoptosis. Fluorescence-activated cell sorter (FACS) analysis revealed that the activation-induced cell death (AICD) caused by anti-CD3 mAb alone, or by a combination of anti-CD3 mAb and FN, occurred selectively in CD4+ CD8+ thymocytes. Very late activation antigen (VLA)-4 and VLA-5 are two major ligands to FN on thymocytes. The expression of both ligands was investigated at different stages of thymocyte development. VLA-4 was predominantly expressed at the CD4- CD8- stage, and thereafter the expression was reduced, whereas VLA-5 was constantly expressed during maturation. Furthermore, the enhancing effect by FN was inhibited in the presence of the Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) peptide but not in the presence of the connecting segment-1 (CS-1) peptide, suggesting that enhancement of AICD observed in CD4+ CD8+ thymocytes is mediated through VLA-5.

Animals↗
PubMed1999

Different roles for LFA-1 and VLA-4 integrins in T-B-cell interactions in vivo.

Adhesion molecules are critical in the cellular interactions involved in specific immune responses. They are used for homing, cell migration, cell-cell contact and, in some cases, for the delivery of costimulatory signals. Since the host-versus-graft (HVG) reaction represents a particular form of T-B-cell interaction, we have explored whether the inhibition of lymphocyte function-associated antigen-1/intracellular adhesion molecule-1 (LFA-1/ICAM-1) interactions and the signalling through very late activation antigen-4 (VLA-4) have any effect on the development of a lupus-like disease in BALB/c mice injected at birth with (BALB/cxC57BL/6)F1 spleen cells. In close association with the development of tolerance to donor allografts, these mice show a polyclonal activation of F1 donor B cells by alloreactive host CD4+ T cells, manifested by the production of autoantibodies (autoAbs) and the development of a mild glomerulonephritis. The dose of the monoclonal antibody (mAb) employed has been adjusted to block completely the molecule on the surface of peripheral lymphocytes without interfering with the induction of neonatal tolerance. Injection of saturating doses (100 microg/2 days) of either anti-LFA-1alpha or anti-ICAM-1 mAbs, but not anti-VLA-4alpha or anti-LFA-1beta mAbs, blocks the production of anti-ssDNA autoAbs and the thrombocytopenia characteristic of this HVG disease (HVGD). However, anti-VLA-4alpha treatment is only able to delay the production of autoAbs and the anti-LFA-1beta treatment, not to modify the evolution of the HVGD. These results point to the relevance of LFA-1/ICAM-1 interactions, but not of the VLA-4-mediated signal, in the polyclonal B-cell activation occurring during the allogeneic interactions between host T helper type 2 cells and donor B cells in HVGD.

Animals↗
PubMed1999

In vivo microscopy of murine islets of Langerhans: increased adhesion of transferred lymphocytes to islets depends on macrophage-derived cytokines in a model of organ-specific insulitis.

Environmental factors contribute to the pathogenesis of type 1 diabetes (insulin-dependent diabetes mellitus). Multiple low doses of streptozotocin (MLDS) induce hyperglycaemia and insulitis in mice. Previously we demonstrated that adhesion of lymphocytes to endothelium of islets is only increased when donor animals were diabetic and recipient mice had received 5 mg/kg streptozotocin (STZ). Therefore we used streptozotocin to evaluate the immunological relevance of such an irritation of islets. Lymphocytes, separated from diabetic mice (MLDS), were fluorescently labelled and injected to recipient mice that had received 5 mg/kg STZ. With in vivo microscopy we measured lymphocyte flow and adherence in islets. Expression of vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1) in the pancreas was assessed using immunohistochemistry. Very late antigen-4 (VLA-4) and leucocyte function-associated antigen-1 (LFA-1) expression on transferred lymphocytes was measured with flow cytometry. Pretreatment of recipients with antibodies to cytokines or silica reduced lymphocyte adherence to islet endothelium from 2.04% (goat immunoglobulin G; IgG) or 1.82% (rat IgG) to 0.47, 0.58, 0.39 or 0. 19% for monoclonal antibody (mAb) interferon-gamma (IFN-gamma), polyclonal antibody (pAb) tumour necrosis factor-alpha (TNF-alpha), pAb interleukin (IL)-1alpha or silica, respectively. Reduced adhesion was associated with a decreased expression of VCAM-1 and ICAM-1 in islets of treated recipients compared with mice treated with 5 mg/kg STZ alone. In conclusion, pretreatment of recipients with 5 mg/kg STZ leads to an increased expression of adhesion molecules in the islets and lymphocyte adhesion to islet endothelium in vivo, demonstrating an immune response of the islets. Prevention of increased expression of ICAM-1 or VCAM-1 and reduction of lymphocyte adhesion in islets by silica or antibody indicate an involvement of macrophages and macrophage derived cytokines in the generation of this immune response.

Animals↗
PubMed1999

CD44 is involved in selective leucocyte extravasation during inflammatory central nervous system disease.

Clinical signs of experimental autoimmune encephalomyelitis (EAE) are associated with the selective recruitment of CD4+ memory (CD45RBlow CD44high) T cells into the central nervous system (CNS). However, we have found that many of these recently recruited memory cells are CD44low, suggesting that the CD44 antigen may be involved in, and transiently lost during, the extravasation process. Indeed, administration of a CD44-specific antibody (IM7.8.1) induced leucocyte CD44 shedding and both prevented the development and ameliorated the severity of established EAE by inhibiting mononuclear cell infiltration into the CNS. Trafficking of cells into lymph nodes, however, a property mainly of naïve cells, was essentially unaffected. In contrast, treatment with antibody to very late activation antigen-4 (VLA-4) prevented homing to both the CNS and to lymph nodes. This study contests previous reports that dismissed a role for CD44 in inflammation of the CNS and, coupled with observations in murine dermatitis and arthritis, suggests that CD44 is involved in the homing of primed lymphocytes to sites of inflammation. CD44 should therefore be considered a target for immunotherapy of T-cell-mediated inflammatory diseases, such as multiple sclerosis.

Animals↗
PubMed2000

Disaccharides generated from heparan sulphate or heparin modulate chemokine-induced T-cell adhesion to extracellular matrix.

We have found previously that disaccharides (DS) enzymatically generated from heparin or heparan sulphate can modulate tumour necrosis factor-alpha (TNF-alpha) secretion from immune cells in vitro and cell-mediated immune reactions in vivo. Here, we show that such DS can modulate the adhesion and migration of human T cells. We found that certain heparin- and heparan sulphate-derived DS induced, in a dose-dependent manner, the adhesion of human T cells to both extracellular matrix (ECM) and immobilized fibronectin (FN); maximal T-cell adhesion occurred with 1 ng/ml of DS. The levels of T-cell adhesion to ECM that were induced by the tested DS molecules resembled those induced by the prototypic chemokine, macrophage inflammatory protein 1beta (MIP-1beta). However, the kinetics of DS-induced T-cell adhesion to FN resembled that induced by phorbol myristate acetate (PMA), but not that induced by MIP-1beta. This adhesion appeared to involve beta1 integrin recognition and activation, and was associated with specific intracellular activation pathways. Although a first exposure of T cells to certain DS molecules appeared to result in cell adhesion, a subsequent exposure of T cells to pro-adhesive chemokines, such as MIP-1beta or RANTES, but not to other pro-adhesive stimuli, for example interleukin-2 or CD3 cross-linking, resulted in inhibition of T-cell adhesion to and chemotactic migration through FN. Hence, we propose that the breakdown products of tissues generated by inflammatory enzymes are part of an intrinsic functional programme, and not necessarily molecular waste. Moreover, because the DS molecules exert their modulatory functions within a limited time, it appears that the historical encounters of the tissue-invading cells with the constituents of inflamed loci may dictate the cells' behaviour upon subsequent exposure to proinflammatory mediators.

Antibodies, Monoclonal↗
PubMed2000

Fibronectin synthesis by activated T lymphocytes: up-regulation of a surface-associated isoform with signalling function.

Fibronectin (FN) is a major constituent of the extracellular matrix. We now provide evidence for a surface-associated isoform of FN that is synthesized by T cells upon activation. The T-cell-derived FN has an unusual splice pattern: an additional domain, EDB, is produced whereas sequences within another domain, IIICS, are spliced out. CS1, the binding domain for very late antigen-4 (VLA-4), however, is still generated. To study the potential function of surface-associated FN its synthesis was down-regulated by an antisense oligonucleotide, then proliferation of T cells was induced by cross-linked anti-CD3. Proliferation was reduced as was expression of CD25. Moreover, when T cells were cultured in high density, the synthetic peptide QILDVPST, corresponding to CS1, inhibited proliferation, as did antibodies to VLA-4. We propose that surface-associated FN is a ligand for VLA-4, which by binding to VLA-4 on an adjacent cell, provides a costimulatory signal, thus sustaining T-cell proliferation.

Antibodies, Monoclonal↗
PubMed2001

Involvement of complement and fibronectin in eosinophil-mediated damage to Nippostrongylus brasiliensis larvae.

By using IL-5 transgenic mice, it has been shown that eosinophils might play a key role in elimination of larval stages of nematode infections. The present study was carried out to clarify molecular mechanisms involved in the eosinophil-mediated killing of Nippostrongylus brasiliensis larvae. The larvicidal activity was observed in the presence of normal serum in vitro. Electron microscopic observations revealed firm attachment of eosinophils to the cuticular surface of larvae, which was damaged by electron-dense materials released from eosinophils. The larvicidal activity was abrogated by heat- or zymosan-treatment of the serum, whereas depletion of IgG or IgM from the serum did not interfere with eosinophil adhesion and killing. Moreover, pretreatment of eosinophils with monoclonal antibodies against CD11b or VLA-4 inhibited the eosinophil-mediated killing of larvae. Immunofluorescent staining demonstrated the deposition of C3c and plasma fibronectin on the cuticle of the larvae. These results indicate that interactions between CD11b and VLA-4 and their respective counter-ligands deposited on the cuticle are essential in eosinophil-mediated adhesion and damage to larvae of N. brasiliensis.

Animals↗
PubMed1996

Regulation of alpha 4 integrin avidity in human B cells: requirement for dephosphorylation events for high avidity VCAM-1 binding.

The authors compared the phosphorylation-dependent signal transduction pathways involved in the regulation of adhesiveness of integrin LFA-1 with that of alpha 4 integrins binding to VCAM-1. The authors developed an in vitro method to monitor changes in adhesiveness using a VCAM-1 fusion protein coupled to magnetic beads. For LFA-1, a similar method has previously been established using an ICAM-1 fusion protein. Binding of cells was monitored and found to be strictly integrin alpha 4 and VCAM-1 dependent. The serine/threonine phosphatase inhibitors okadaic acid and calyculin A were equally potent in inhibiting binding to VCAM-1 as to ICAM-1, and inhibition of protein phosphatase-1 (PP1) is proposed to be the important denominator. Similarly, the phorbol ester PDBu, potentially stimulating protein phosphatase-1 and staurosporine, an inhibitor of serine/threonine kinases, enhanced adhesion to VCAM-1 as has previously been shown for ICAM-1. A major difference was that a significant portion of the binding to VCAM-1 was not susceptible to inhibition by drugs while binding to ICAM-1 could be completely inhibited. We propose that the adhesiveness of the alpha 4 integrins for VCAM-1 and of LFA-1 for ICAM-1 is regulated by similar or identical protein kinases and phosphatases.

B-Lymphocytes↗
PubMed2001

Downmodulation of CD18 and CD86 on macrophages and VLA-4 on lymphocytes in experimental tuberculosis.

Development and evaluation of new vaccines and immunotherapy against tuberculosis demand a better understanding of the immune mechanisms in this disease. Costimulatory signals and intercellular contact seem to be pivotal in determining whether recognition of antigen by T cells leads to activation or anergy. In this paper, we show that virulent M. tuberculosis H37Rv downmodulates the ex vivo expression of CD18 and CD86 on peritoneal macrophages and VLA-4 on lymphocytes but does not disturb the in vitro production of interleukin (IL)-12 and interferon (IFN)-gamma after intraperitoneal infection. In addition, splenocytes from infected mice produce IL-10, while the expression of cell surface receptors is unchanged. The interplay among IL-12, IFN-gamma and IL-10 in vivo and the downmodulation of cell-surface receptors during the infection at the inflammatory site may contribute to the explanation of the maintenance of infection.

Animals↗