Leucocyte adhesion molecules.
Explore the source record for details and available documents.
Antigens, Surface↗
SEARCH · PubMed Health
Results for “Integrin alphaXbeta2”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Effects of monocyte purification and culture on integrin expression.
Selective alterations in the surface expression of members of the LeuCAM (leukocyte cell adhesion molecule) family of integrins occur during in vitro culture of human monocytes. Such changes may relate in part to cellular maturation, but also to activation following purification and culture of monocytes. In this paper, we examined the effects of monocyte isolation, adherence during culture and endotoxin exposure on the expression of these molecules and the ligand for LFA-1, ICAM-1 (CD54). Expressions of CD11b, CD18 and CD54, but not CD11a or CD11c, were higher on monocytes freshly isolated by density gradient separation and plastic adherence as compared with cells labelled directly in whole blood. However, the surface expression of the LeuCAMs and CD54 on cultured monocytes was not affected by short-term adherence to plastic for 2 h, as determined by comparisons of their expression on adherence-isolated and elutriated monocytes. In contrast, prolonged adhesion of monocytes for up to 21 days in culture altered expression of CD11a without affecting that of the other LeuCAMs or CD54. Expression of CD11a decreased more rapidly on adherence-maintained cells as compared with suspension-cultured cells. Our results show that cellular manipulations required for in vitro studies of monocyte/macrophages may alter expression of the LeuCAMs.
CD18 Antigens↗
Role of alpha4 integrin and VCAM-1 in CD18-independent neutrophil migration across mouse cardiac endothelium.
Myocardial damage due to reperfusion of ischemic tissue is caused primarily by infiltrating neutrophils. Although leukocyte beta2 integrins (CD18) play a critical role, significant neutrophil emigration persists when CD18 is neutralized or absent. This study examined the role of leukocyte beta1 integrin (alpha4) and its endothelial ligand VCAM-1 in CD18-independent neutrophil migration across cardiac endothelium. In a mouse model of myocardial ischemia and reperfusion, we show that compared with wild-type mice, neutrophil infiltration efficiency was reduced by 50% in CD18-null mice; in both types of mice, myocardial VCAM-1 staining increased after reperfusion. In wild-type mice, antibodies against CD18, ICAM-1 (an endothelial ligand for CD18), or VCAM-1 given 30 minutes before ischemia did not block neutrophil emigration at 3 hours reperfusion. Although anti-VCAM-1 attenuated neutrophil emigration by 90% in CD18-null mice, it did not diminish myocardial injury. To determine if CD18-independent neutrophil emigration was a tissue-specific response, we used isolated peripheral blood neutrophils from wild-type or CD18-null mice and showed neutrophil migration across lipopolysaccharide-activated cultured cardiac endothelium is CD18-independent, whereas migration across endothelium obtained from inferior vena cava is CD18-dependent. Consistent with our in vivo findings, migration of CD18-deficient neutrophils on cardiac endothelial monolayers is blocked by antibodies against alpha4 integrin or VCAM-1. We conclude tissue-specific differences in endothelial cells account, at least partially, for CD18-independent neutrophil infiltration in the heart.
Animals↗
Neutrophil transmigration across human airway epithelial monolayers: mechanisms and dependence on electrical resistance.
To examine neutrophil transepithelial migration in the basolateral-to-luminal direction, bronchial epithelial cells (16HBE) were grown at an air-medium interface on the lower face of permeable supports, and resistance across each membrane was recorded before measuring neutrophil transmigration over 2 h. Subconfluent monolayers (resistance < 250 Omega) permitted high spontaneous migration of neutrophils (7.4+/-1%), which was further enhanced (29.7+/-3%) in response to interleukin (IL)-8 (100 ng/ml). Confluent monolayers (250 to 700 Omega) showed low spontaneous migration (2+/- 0.5%) but responded markedly to IL-8 (12.4+/-1.3%). Left in culture, 16HBE resistances continued to increase and were associated with minimal spontaneous migration (< 0.5%) or responses to IL-8. Using cells in the 250 to 700 Omega range, neutrophil migration to IL-8 was dose-dependent and was enhanced when epithelial cells were incubated with a combination of tumor necrosis factor-alpha and interferon-gamma. Neutrophil migration was stimulus-specific and was reduced by preincubation of epithelial cells with a F(ab')(2) anti-intercellular adhesion molecule (ICAM)-1, or by preincubation of neutrophils with anti-CD18, anti-CD11a, anti-CD11b, or anti-CD11c, but not by anti-CD11d, indicating a role for beta(2)-integrin-ICAM-1 interaction in the migration process.
Antibodies↗
Effects of heparin coating on the expression of CD11b, CD11c and CD62L by leucocytes in extracorporeal circulation in vitro.
Leucocyte adhesion molecules are involved in the leucocyte-endothelial interaction and in the activation of coagulation and binding of complement and endotoxin. Thus, they are important in inflammation, systemic acute phase reaction, ischaemia reperfusion injury and resistance against infections. The expression of the adhesion molecules CD11b, CD11c and CD62L on leucocytes and changes in plasma products of neutrophil activation (myeloperoxidase, lactoferrin) and complement activation (C3bc, SC5b-9 (TCC)) were examined in an extracorporeal circulation (ECC) model and the effects of Carmeda bioactive surface (CBAS) heparin coating (n = 7) of the circuits were compared to uncoated control circuits (n = 5). In this model, new 'unactivated' cells mobilized from the bone marrow could not interfere with descriptive measures of cell activation as seen in in vivo studies. In the control group, CD11b and CD11c were upregulated on monocytes and granulocytes during ECC, whereas CD62L was downregulated. Heparin coating reduced the increase in CD11b and CD11c on granulocytes (p < 0.02 at 2 h), but the delayed increase in CD11c on monocytes and the delayed downregulation of CD62L on granulocytes and monocytes did not reach statistical significance. Further, heparin coating also reduced the initial decrease in the absolute cell counts of monocytes and granulocytes (p = 0.01 at 2 h), reflecting reduced adhesion to the oxygenator/tubing. The increases in plasma myeloperoxidase, lactoferrin, C3bc and TCC were lower in the heparin-coated group compared to the control group. The increases in plasma myeloperoxidase and lactoferrin correlated significantly to the increase in CD11b (r = 0.71, p = 0.02 and r = 0.64, p = 0.05, respectively) and CD11c (r = 0.72, p = 0.008 and r = 0.72, p = 0.008, respectively) on granulocytes, suggesting interacting regulatory pathways in the process of neutrophil adhesion, activation and degranulation. Thus, in this in vitro ECC model, heparin coating of oxygenator/tubing sets reduced leucocyte activation and leucocyte adhesion-related phenomena.
Blood Cell Count↗
The apoptotic-cell receptor CR3, but not alphavbeta5, is a regulator of human dendritic-cell immunostimulatory function.
Dendritic cells (DCs) that capture apoptotic cells (ACs) in the steady state mediate peripheral tolerance to self-antigens. ACs are recognized by an array of receptors on DCs, the redundancy of which is not completely defined. We made use of an AC surrogate system to address the individual roles of the alphavbeta5 and complement receptors (CRs) in the phagocytosis and induction of immunity. CR3 and CR4, while substantially less efficient than alphavbeta5 in internalizing ACs, initiate signals that render DCs tolerogenic. Responding T cells show impaired proliferation and IFNgamma production and subsequently die by apoptosis. While tolerogenic DCs are not induced via alphavbeta5, coligation of CR3 and alphavbeta5 maintains the DC's tolerogenic profile. This immunomodulatory role, however, is countered by a significant inflammatory stimulus such as bacterial infection. Overall, our data suggest that under steady-state conditions, signaling via CRs predominates to render DCs tolerogenic.
Apoptosis↗
Endothelial cell activation by myeloblasts: molecular mechanisms of leukostasis and leukemic cell dissemination.
Leukostasis and tissue infiltration by leukemic cells are poorly understood life-threatening complications of acute leukemia. This study has tested the hypothesis that adhesion receptors and cytokines secreted by blast cells play central roles in these reactions. Immunophenotypic studies showed that acute myeloid leukemia (AML) cells (n = 78) of the M0 to M5 subtypes of the French-American-British Cooperative Group expressed various amounts of adhesion receptors, including CD11a, b, c/CD18, CD49d, e, f/CD29, CD54, sCD15, and L-selectin. The presence of functional adhesion receptors was evaluated using a nonstatic adhesion assay. The number of blast cells attached to unactivated endothelium increased by 7 to 31 times after a 6-hour exposure of endothelium to tumor necrosis factor (TNF)-alpha. Inhibition studies showed that multiple adhesion receptors--including L-selectin, E-selectin, VCAM-1, and CD11/CD18--were involved in blast cell adhesion to TNF-alpha-activated endothelium. Leukemic cells were then cocultured at 37 degrees C on unactivated endothelial cell monolayers for time periods up to 24 hours. A time-dependent increase in the number of blasts attached to the endothelium and a concomitant induction of ICAM-1, VCAM-1, and E-selectin were observed. Additional experiments revealed that endothelial cell activation by leukemic myeloblasts was caused by cytokine secretion by blast cells, in particular TNF-alpha and IL-1 beta, and direct contacts between adhesion receptors expressed by blast cells and endothelial cells. Thus, leukemic cells have the ability to generate conditions that promote their own adhesion to vascular endothelium, a property that may have important implications for the pathophysiology of leukostasis and tissue infiltration by leukemic blast cells. (Blood. 2001;97:2121-2129)
Antigens, CD↗
Production of inducible nitric oxide is required for monocytic differentiation of U937 cells induced by vitamin E-succinate.
Many putative differentiating agents arrest cell growth prior to progression of the cell through differentiation. Vitamin E-succinate is known to be a potent modulator of haematopoietic differentiation as well as an inhibitor of cell growth in vitro and in vivo. In this study, we examined whether vitamin E-succinate could modulate the monocytic differentiation of U937 human monoblasts. Treatment with vitamin E-succinate for 1-4 days inhibited the proliferation of U937 cells. Vitamin E-succinate also induced monocytic differentiation as indicated by the increase in nitro blue tetrazolium reduction activity, and the expression of monocyte specific cell surface antigen, CD11c, and integrins alpha5 and beta1. The monocytic differentiation of U937 cells was also induced when the cells were cultured in fibronectin-coated wells. Monocytic differentiation was enhanced when the cells were treated with both vitamin E-succinate and fibronectin, suggesting that vitamin E-succinate and fibronectin synergistically act on monocytic differentiation of U937 cells. During monocytic differentiation of U937 cells induced by vitamin E-succinate and/or fibronectin, nitric oxide was detected in supernatants. The production of nitric oxide was not detected when monocytic differentiation of U937 cells was induced by phorbol-12 myristate 13-acetate, a well known inducer of macrophage-like cell differentiation. Vitamin E-succinate and/or fibronectin induced monocytic differentiation was blocked by the treatment of nitric oxide synthase inhibitor, N-G-monomethyl-L-arginine. In contrast, treatment of cells with sodium nitroprusside, a chemical nitric oxide donor, stimulated monocytic differentiation of U937 cells at an early time point. Taken together, these results suggest that nitric oxide is an important intermediator at an early stage of vitamin E-succinate- and/or fibronectin-induced monocytic differentiation of U937 cells.
Antigens, CD↗
Lipophosphoglycan from Leishmania mexicana promastigotes binds to members of the CR3, p150,95 and LFA-1 family of leukocyte integrins.
The abundant surface glycolipid, promastigote lipophosphoglycan (LPG), of Leishmania promastigotes was isolated and reconstituted onto the surface of hydrophobic silica beads. These beads bound to both macrophages and monocytes, suggesting that phagocytes possess a receptor(s) capable of recognizing LPG. LPG beads were unable to bind to macrophages isolated from individuals with a genetic deficiency in the CD18 complex of leukocyte integrins (CR3, p150,95, and LFA-1), suggesting that one or more of these receptors were required for binding of LPG. Individual members of the CD18 complex were depleted from macrophages by plating cells on surfaces coated with anti-receptor mAb. These experiments indicated that CR3 and p150,95 from the CD18 complex, were the predominant mediators of attachment of LPG. The phagocyte receptor CR3 expresses two distinct binding sites, one that binds peptide ligands, such as C3bi, and a second site, that recognizes bacterial LPS. Antibody inhibition experiments and competition binding studies with synthetic peptides and soluble LPG indicated that LPG is recognized by the nonpeptide, or "LPS" binding site on CR3.
Animals↗
Integrin distribution and cytoskeleton organization in normal and malignant monocytes.
In this work we have mapped by double-label immunofluorescence the cellular distribution of integrins and their relationship with cytoskeletal proteins in normal and malignant monocytes. In normal monocytes, CD18 and CD11c are concentrated at specific adhesion sites, named podosomes, together with actin, vinculin, and talin, while CD11a, CD11b, CD29/beta 1, CDw49d/alpha 4 and CD54/ICAM-1 retain a diffuse distribution on the cell surface without a selective pattern of localization. U-937 and fresh leukemic monoblasts under standard culture conditions do not adhere and do not form podosomes, but, when treated with TPA, they promptly adhere to substrate, form podosomes and focal adhesions in different cells and display the same integrin/cytoskeleton relationship as normal mature monocytes. Further, in these cells CD18, CD11a, CD11c, ICAM-1, and talin, but not vinculin, co-localize in homotypic cell junctions, thus showing a close relationship between integrins and talin. These observations provide morphological evidence that, in cells of the monocytic lineage, podosome formation is acquired upon differentiation and different integrins are selectively localized at different adhesion sites.
CD18 Antigens↗
Current status review: adhesion molecules and myelomonocytic cell-endothelial interactions.
Explore the source record for details and available documents.
Antibodies, Monoclonal↗
An octamer element functions as a regulatory element in the differentiation-responsive CD11c integrin gene promoter: OCT-2 inducibility during myelomonocytic differentiation.
The integrin CD11c/CD18 mediates leukocyte adhesion to endothelium and other cell types and is a receptor for LPS, iC3b, and fibrinogen. CD11c expression is restricted to myeloid and activated B cells, is regulated during leukocyte differentiation, and constitutes a diagnostic tool for hairy cell leukemia. Mapping of in vivo DNA-protein interactions in the CD11c proximal promoter revealed three adjacent myeloid-specific interactions, one of which lies on an octamer consensus sequence, ATTT GCAT (Oct185). Oct185 disruption increased the CD11c promoter activity while decreasing its myeloid differentiation responsiveness, indicating that Oct185 contributes to the activity of the CD11c promoter and suggesting that Oct185 is a negative regulatory element whose function changes during myeloid differentiation. Oct185 is recognized by the ubiquitous Oct-1 factor in all cell lineages and by Oct-2 in B lymphoid lineage cells. Unexpectedly, Oct-2 binding to Oct185 was induced de novo upon monocytic differentiation of U937 and HL-60 cells but not during HL-60 granulocytic differentiation, as determined by electrophoretic mobility shift assays and immunochemical studies, and Oct-2 complexes were also observed in cultured adherent monocytes. Western blotting showed that the pattern of Oct-2 isoforms in myeloid cells is similar to that seen in B cells. The Oct-2 up-regulated expression in differentiating myeloid cells and its binding to the Oct185 negative regulatory element suggests its involvement in the differentiation-regulated activity of the CD11c promoter and might represent an important parameter for the myeloid- and B cell-restricted expression of the CD11c/CD18 integrin and other molecules with similar patterns of expression.
Blotting, Western↗
Integrin-using rotaviruses bind alpha2beta1 integrin alpha2 I domain via VP4 DGE sequence and recognize alphaXbeta2 and alphaVbeta3 by using VP7 during cell entry.
Integrins alpha2beta1, alphaXbeta2, and alphaVbeta3 have been implicated in rotavirus cell attachment and entry. The virus spike protein VP4 contains the alpha2beta1 ligand sequence DGE at amino acid positions 308 to 310, and the outer capsid protein VP7 contains the alphaXbeta2 ligand sequence GPR. To determine the viral proteins and sequences involved and to define the roles of alpha2beta1, alphaXbeta2, and alphaVbeta3, we analyzed the ability of rotaviruses and their reassortants to use these integrins for cell binding and infection and the effect of peptides DGEA and GPRP on these events. Many laboratory-adapted human, monkey, and bovine viruses used integrins, whereas all porcine viruses were integrin independent. The integrin-using rotavirus strains each interacted with all three integrins. Integrin usage related to VP4 serotype independently of sialic acid usage. Analysis of rotavirus reassortants and assays of virus binding and infectivity in integrin-transfected cells showed that VP4 bound alpha2beta1, and VP7 interacted with alphaXbeta2 and alphaVbeta3 at a postbinding stage. DGEA inhibited rotavirus binding to alpha2beta1 and infectivity, whereas GPRP binding to alphaXbeta2 inhibited infectivity but not binding. The truncated VP5* subunit of VP4, expressed as a glutathione S-transferase fusion protein, bound the expressed alpha2 I domain. Alanine mutagenesis of D308 and G309 in VP5* eliminated VP5* binding to the alpha2 I domain. In a novel process, integrin-using viruses bind the alpha2 I domain of alpha2beta1 via DGE in VP4 and interact with alphaXbeta2 (via GPR) and alphaVbeta3 by using VP7 to facilitate cell entry and infection.
Amino Acid Motifs↗
Surface adhesion molecule expression on human blood cells induced by vascular graft materials in vitro.
The expression of surface adhesion molecules on granulocytes, monocytes (CD11a, CD11b, CD11c, CD18, L-selectin), and platelets (P-selectin, gpIIb-IIIa) was determined after incubation with different graft surfaces [expanded polytetrafluoroethylene (ePTFE) or woven Dacron]. Woven Dacron grafts upregulated the CD11b and CD11c surface antigens on both granulocytes and monocytes. Both graft materials demonstrated increased expression of CD11a and CD18 adhesion molecules on white blood cells at 30 min, followed by a downregulation. Maximum L-selectin expression was seen at 120 min on granulocytes and at 90 min on monocytes without differences between the graft materials. A rapid downregulation of gpIIb-IIIa complexes on platelets was noticed, while no expression of platelet P-selectin molecules was observed. In conclusion, both graft materials induced alteration of the white blood cell adhesion molecule expression, but the intensity and time course were dependent on the cell type and the graft material, suggesting that different mechanisms might be implicated. The expression of platelet surface antigens was less clearly influenced. The clinical significance of an enhanced cell surface antigen receptor expression caused by woven Dacron (CD11b, CD11c) has to be further studied. However, determination of adhesion molecule expression might offer possibilities to predict biocompatibility.
Blood Platelets↗
Expression of a homologue of rat NG2 on human microglia.
The expression of NG2 chondroitin sulfate has been widely associated with oligodendrocyte precursors in rodents. We used a monoclonal antibody (9.2.27) against the human homologue of the rat NG2 to determine whether expression of this molecule was associated with a specific glial cell population present in dissociated cell preparations derived from adult and fetal human brain tissue. Our data, derived using FACS and immunocytochemical analyses of immediately ex vivo or cultured glial cells, indicate that the large majority of NG2 expressing cells belonged to the microglial lineage (CD68, CD11c) rather than to the oligodendrocyte lineage (O4, A2B5, GalC). In situ immunohistochemistry performed on non-fixed normal spinal cord tissue confirmed the observation that NG2 is expressed by mononuclear phagocytes of the CNS. In contrast, peripheral blood-derived monocytes were NG2(-). Cells from fetal brain tissue showed only small numbers of NG2(+) cells, which was consistent with the number of microglial cells in this preparation. In absence of additional markers, we cannot exclude that this anti-NG2 mAb might also recognize human oligodendrocyte progenitor cells.
Adult↗
Expression of the H52 epitope on the beta2 subunit is dependent on its interaction with the alpha subunits of the leukocyte integrins LFA-1, Mac-1 and p150,95 and the presence of Ca2+.
Integrin-mediated adhesion is a divalent cation-dependent process. Whether divalent cations directly participate in ligand binding or exert their effects indirectly by affecting the overall structure of the integrin heterodimers is not known. In this study we describe the epitope of the mAb H52 which has been mapped to a predicted disulfide-bonded loop (C386 and C400) in the beta2 integrin subunit. In the presence of Ca2+ and Mg2+, the H52 epitope is expressed on the monomeric beta2 subunit, the LFA-1 and Mac-1 heterodimers but not on p150,95, thus implying that this epitope is masked in p150,95. However, expression of the H52 epitope on Mac-1, but not on LFA-1, or the monomeric beta2 subunit, is dependent on the presence of Ca2+, thus suggesting that the chelation of Ca2+ causes a conformational change in Mac-1 which results in the loss of the epitope. These results suggest that expression of the H52 epitope on the beta2 subunit is dependent on its interaction with the different alpha subunits. Since the epitope itself is not required for heterodimer formation nor for ligand binding, occupancy of a Ca2+ binding site(s) must therefore affect the alphabeta subunit interactions, and thus the overall conformation of Mac-1.
Amino Acid Sequence↗
Salmonella efficiently enter and survive within cultured CD11c+ dendritic cells initiating cytokine expression.
While Salmonella infects macrophages, this cell population may not be the only one important for disseminating intracellular bacteria from mucosal sites. Dendritic cells (DC) are present in the Peyer's patches and are mobilized following stimulation. Such characteristics would seem to be ideal for the dissemination of an intracellular, mucosal pathogen. However, it has been difficult to obtain sufficient numbers of DC to assess their ability to harbor Salmonella or to monitor DC in vivo. In the present study, this problem has been addressed by expanding DC in vivo using flt3 ligand, followed by the purification of CD11c+ cells using antibody-coated magnetic beads or by fluorescence-activated cell sorting. Salmonella dublin were found to be efficiently internalized, and to survive and replicate within purified CD11c+ DC, and also in CD11c+, CD8alpha+ or CD11c+, CD11b+ DC subpopulations. The ability of Salmonella to enter DC is of similar magnitude to that reported for macrophages, suggesting that this cell population could be an important host cell for dissemination of this pathogen from mucosal sites. Furthermore, infected DC responded to Salmonella by secretion of IL-1, IL-6 and IL-12. As such, these cells may be important sources of these cytokines during the host response against Salmonella infection.
Animals↗
CD4 T cell traffic control: in vivo evidence that ligation of OX40 on CD4 T cells by OX40-ligand expressed on dendritic cells leads to the accumulation of CD4 T cells in B follicles.
We report here that CD40- but not lipopolysaccharide (LPS)-activated murine dendritic cells (DC) express OX40-ligand (OX40L) as has been reported in humans. To understand how OX40 ligation affects differentiation of CD4 T cells at the time of priming, we constitutively expressed OX40L on DC using the DC-specific promoter of CD11c. Transgenic mice showed greatly increased numbers of CD4 but not CD8 T cells in their B cell areas. This effect was to a great extent immunization dependent, as spleen and lymphoid tissue with no germinal center reactions from mice which had not been deliberately immunized did not show marked CD4 T cell accumulation. The increased numbers of CD4+ CD62low cells in transgenic mice suggest that it is activated CD4 T cells that accumulate within B cell follicles. These data are consistent with the notion that physiological engagement of OX40 (CD134) on activated CD4 T cells either initiates their migration into or causes them to be retained in B follicles. In contrast, LPS-treated CD did not up-regulate OX40L expression. This dichotomy provides a molecular explanation of how DC might integrate environmental and accessory signals to control cytokine differentiation and migration in CD4 effector cells.
Animals↗