(1/437) Does soluble intercellular adhesion molecule-1 (ICAM-1) affect neutrophil activation and adhesion following ischaemia-reperfusion?
OBJECTIVES: To examine the effect of reperfusion plasma and sICAM-1 on neutrophil integrin expression and neutrophil adhesion to determine if sICAM-1 has a potential role in the regulation of neutrophil adhesion. MATERIALS: Twenty-seven patients, 17 men and 10 women undergoing femorodistal surgery. Blood was taken preoperatively and from the femoral vein following the release of the cross-clamp. Neutrophils were obtained from five volunteers and incubated with phosphate buffered saline (PBS), preoperative plasma or reperfusion plasma with and without sICAM-1. Neutrophil expression of CD11b and adhesion were measured. MAIN RESULTS: Neutrophil CD11b expression did not change following incubation in the three media. Neutrophil adhesion increased significantly following exposure to reperfusion plasma compared to PBS or preoperative plasma (45.5 adhesion vs. 12.75%, p < 0.01 Mann-Whitney U-test). Soluble ICAM-1 decreased CD11b expression and adhesion in neutrophils exposed to reperfusion plasma only (CD11b expression fell from 15.9 to 3.4 mcf, p < 0.01 Mann-Whitney U-test and adhesion fell to 11.6% cells adhered, p < 0.01). CONCLUSION: An increase in CD11b expression is not required for an increase in neutrophil adhesion. The change in neutrophil adhesion produced by reperfusion plasma can be blocked by sICAM-1. Soluble ICAM-1 may have a physiological role in the regulation of neutrophil adhesion. (+info)
(2/437) Phenotypic analysis of lymphocytes and monocytes/macrophages in peripheral blood and bronchoalveolar lavage fluid from patients with pulmonary sarcoidosis.
BACKGROUND: The granulomatous inflammation in sarcoidosis is driven by the interplay between T cells and macrophages. To gain a better understanding of this process the expression by these cells of cell surface activation markers, co-stimulatory molecules, and adhesion molecules was analysed. METHODS: CD4+ and CD8+ T lymphocytes from peripheral blood (PBL) or bronchoalveolar lavage (BAL) fluid, as well as paired peripheral blood monocytes and alveolar macrophages from 27 patients with sarcoidosis were analysed by flow cytometry. RESULTS: CD26, CD54, CD69, CD95, and gp240 were all overexpressed in T cells from BAL fluid compared with those from PBL in both the CD4+ and CD8+ subsets, while CD57 was overexpressed only in BAL CD4+ cells. In contrast, CD28 tended to be underexpressed in the BAL T cells. Monocyte/macrophage markers included CD11a, CD11b, CD11c, CD14, CD16, CD54, CD71, CD80 and CD86 and HLA class II. CD11a expression in alveolar macrophages (and peripheral blood monocytes) was increased in patients with active disease and correlated positively with the percentage of BAL lymphocytes. Expression of CD80 in macrophages correlated with the BAL CD4/CD8 ratio. CONCLUSIONS: Our data indicate substantial activation of both CD4+ and CD8+ lung T cells in sarcoidosis. There were also increased numbers of BAL lymphocytes whose phenotypic characteristics have earlier been associated with clonally expanded, replicatively senescent cells of the Th1 type. (+info)
(3/437) Maturation and apoptosis of primary human acute myeloblastic leukemia cells are determined by TNF-alpha exclusively through CD120A stimulation.
BACKGROUND AND OBJECTIVE: Tumor necrosis factor-a plays an important role in hematopoiesis. Its effects are mediated through two membrane-bound receptors: TNF-R I (p55; CD 120a) and TNF-R II (p75; CD 120b). The aim of our study was to investigate the relative roles of these receptors. DESIGN AND METHODS: We analyzed in 16 acute myeloid leukemia cases whether TNF-alpha could induce in vitro maturation and apoptosis. We then investigated which of the two receptors was provoking monocytic maturation and which was responsible for apoptosis by using the agonistic MoAb HTR-9, directed at CD120a, and the CD120b antagonistic MoAb UTR-1. RESULTS: Monocytic maturation (morphologic and immunologic) was induced in all cases studied, although to different rates, by TNF-alpha and by HTR-9 incubation. The addition of UTR-1 to TNF-alpha did not abolish maturation, nor did it affect apoptosis, which was present in primary AML cultures after 4 and 10 days. INTERPRETATION AND CONCLUSIONS: We present here evidence that the sole stimulation of CD 120a, but not of CD120b, by TNF-alpha is responsible for bot monocytic maturation and apoptosis of primary AML blasts. (+info)
(4/437) Membrane expression of soluble endotoxin-binding proteins permits lipopolysaccharide signaling in Chinese hamster ovary fibroblasts independently of CD14.
The activation of phagocytes by lipopolysaccharide (LPS) has been implicated in the pathogenesis of Gram-negative sepsis. Although the interaction between CD14 and LPS is a key event in the signaling cascade, the molecular mechanism by which cellular activation occurs remains obscure. We hypothesized that the main function of CD14 was to bind LPS and transfer it to a second receptor, which then initiates the subsequent signal for cellular activation. Thus, surface binding of LPS to the cell membrane would be the critical step that CD14 carries out. To test this hypothesis, we examined the activity of two other proteins known to bind LPS, lipopolysaccharide-binding protein and bactericidal/permeability-increasing protein. We found that when these normally soluble proteins were expressed in Chinese hamster ovary-K1 fibroblasts as glycosylphosphatidylinositol-anchored proteins, both could substitute for CD14 in initiating LPS signaling. Pharmacological studies with synthetic lipid A analogues demonstrated that these surface expressed LPS-binding proteins had characteristics that were qualitatively identical to membrane CD14. These data support the hypothesis that a receptor distinct from CD14 functions as the actual signal transducer and suggest that surface binding of LPS to the cell membrane is the crucial first step for initiating downstream signaling events. (+info)
(5/437) ICAM-2 and a peptide from its binding domain are efficient activators of leukocyte adhesion and integrin affinity.
Cell adhesion mediated by the CD11/CD18 integrins and their ligands, the ICAMs, is required for many leukocyte functions. In resting cells the integrins are nonadhesive, but when activated they become adhesive for their ligands. Previous findings have shown that a peptide derived from the first Ig domain of ICAM-2 (P1) binds to LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) and activates leukocyte aggregation. Because its mechanism of action has remained poorly understood, we have now studied the peptide-induced ligand binding in detail. Here we show that P1 was able to induce CD11/CD18-dependent adhesion of human T lymphocytes to immobilized, purified ICAM-1, -2, and -3. The optimal peptide concentration was 150 micrograms/ml, whereas concentrations higher than 400 micrograms/ml did not have any stimulatory effect. The increase in adhesion was detectable within 10 min of treatment with the peptide; it was dependent on energy, divalent cations, temperature, and an intact cytoskeleton but was unaffected by protein kinase C and protein tyrosine kinase inhibitors. Peptide treatment resulted in strong stimulation of the binding of soluble, recombinant ICAMs to T lymphocytes, showing that the integrin affinity toward its ligands was increased. Importantly, soluble ICAM-2Fc was also able to induce T lymphocyte adhesion to purified ICAM-1, -2, and -3, and it was a more potent stimulatory molecule than ICAM-1Fc or ICAM-3Fc. (+info)
(6/437) Human immunoglobulin A receptor (FcalphaRI, CD89) function in transgenic mice requires both FcR gamma chain and CR3 (CD11b/CD18).
Even though more immunoglobulin A (IgA) is produced in humans than all other isotypes combined, relatively little is known about receptors that bind the Fc part of IgA. The myeloid IgA receptor, FcalphaRI (CD89), triggers various effector functions in vitro, but its in vivo role remains unclear. Here, a transgenic mouse model is described in which FcalphaRI is expressed under its own regulatory sequences. Receptor expression and regulation by cytokines was comparable to the human situation and hFcalphaRI can trigger phagocytosis and lysis of tumor cells. To analyze the contribution of the FcR gamma chain or the beta2 integrin CR3 (CD11b/CD18) in FcalphaRI biological function, FcalphaRI transgenic mice were crossed with either FcR gamma chain -/- or CR3 -/- mice. In contrast to in vitro data, FcR gamma chain was essential for surface expression of hFcalphaRI in vivo. Functional studies in hFcalphaRI/ gamma-/-mice were, therefore, limited. In vitro studies showed FcR gamma chain to be necessary for phagocytosis. Neither hFcalphaRI expression nor phagocytosis, triggered via hFcalphaRI, were influenced by CR3. Remarkably, the capacity to lyse tumor targets was ablated in hFcalphaRI transgenic/ CR3-/- mice, although binding of neutrophils to tumor cells was intact. This shows a previously unrecognized importance of CR3 for hFcalphaRI-mediated antibody-dependent cellular cytotoxicity (ADCC). (+info)
(7/437) Decreased superoxide production, degranulation, tumor necrosis factor alpha secretion, and CD11b/CD18 receptor expression by adherent monocytes from preterm infants.
Preterm infants have an increased incidence of infection, which is principally due to deficiencies in neonatal host defense mechanisms. Monocyte adherence is important in localizing cells at sites of infection and is associated with enhanced antimicrobial functions. We isolated cord blood monocytes from preterm and full-term infants to study their adhesion and immune functions, including superoxide (O2-) generation, degranulation, and cytokine secretion and their adhesion receptors. O2- production and degranulation were significantly diminished, by 28 and 37%, respectively, in adherent monocytes from preterm infants compared to full-term infants (P < 0. 05); however, these differences were not seen in freshly isolated cells. We also observed a significant decrease of 35% in tumor necrosis factor alpha secretion by lipopolysaccharide-stimulated adherent monocytes from preterm infants compared to full-term infants (P < 0.05); however, this difference was not observed in interleukin-1beta or interleukin-6 production by the monocytes. The cell surface expression of the CD11b/CD18 adhesion receptor subunits was significantly decreased (by 60 and 52%, respectively) in monocytes from preterm infants compared to full-term infants (P < 0. 01). The cascade of the immune response to infection involves monocyte upregulation and adherence via CD11b/CD18 receptors followed by cell activation and the release of cytokines and bactericidal products. We speculate that monocyte adherence factors may be important in the modulation of immune responses in preterm infants. (+info)
(8/437) Apo A-I inhibits foam cell formation in Apo E-deficient mice after monocyte adherence to endothelium.
We have previously shown that expression of the human apo A-I transgene on the apo E-deficient background increases HDL cholesterol and greatly diminishes fatty streak lesion formation. To examine the mechanism, prelesional events in atherosclerotic plaque development were examined in 6- to 8-week-old apo E-deficient and apo E-deficient/human apo A-I transgenic mice. A quantitative assessment of subendothelial lipid deposition by freeze-fracture and deep-etch electron microscopy indicated that elevated apo A-I did not affect the distribution or amount of aortic arch subendothelial lipid deposits. Immunohistochemical staining for VCAM-1 demonstrated similar expression on endothelial cells at prelesional aortic branch sites from both apo E-deficient and apo E-deficient/human apo A-I transgenic mice. Transmission electron microscopy revealed monocytes bound to the aortic arch in mice of both genotypes, and immunohistochemical staining demonstrated that the area occupied by bound mononuclear cells was unchanged. Serum paraoxonase and aryl esterase activity did not differ between apo E-deficient and apo E-deficient/human apo A-I transgenic mice. These data suggest that increases in apo A-I and HDL cholesterol inhibit foam cell formation in apo E-deficient/human apo A-I transgenic mice at a stage following lipid deposition, endothelial activation, and monocyte adherence, without increases in HDL-associated paraoxonase. (+info)