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D F Bainton

Publications and source records attributed to D F Bainton.

At least 37 records · Page 2Linked to original sources
PubMed1994

Neutrophil tethering to and rolling on E-selectin are separable by requirement for L-selectin.

Neutrophil tethering and rolling in shear flow are mediated by selectins and have been thought to be two indistinguishable manifestations of a single molecular interaction between selectin and ligand. However, we report that under physiologic flow conditions, tethering to E-selectin requires a ligand distinct from the one that supports neutrophil rolling. Tethering under shear to E-selectin requires a carbohydrate ligand that is closely associated with the lectin domain of L-selectin on the neutrophil surface, as enzymatic removal of L-selectin, chemotactic factor-induced shedding of L-selectin, and L-selectin MAbs effectively block tethering. In contrast, this ligand is dispensable for the ability to roll on E-selectin, since rolling adhesions formed after static incubations were not affected by the presence or absence of L-selectin. Thus, E-selectin interactions with ligands on neutrophils persist after L-selectin shedding. These findings add an additional step for regulation of leukocyte localization in inflammatory sites.

Antibodies, Monoclonal↗
PubMed1994

Activated neutrophils express proteinase 3 on their plasma membrane in vitro and in vivo.

Apart from the diagnostic value of anti-neutrophil cytoplasmic antibodies (ANCA), their detailed characterization and that of their corresponding antigens have opened new ways for the exploration of the pathogenesis of primary systemic vasculitis. ANCA are now thought to play an important functional role via activation of phagocytic cells (e.g. polymorphonuclear neutrophils (PMN)). In this study we examined the mechanisms by which ANCA could gain access to proteinase 3 (PR3) in intact PMN, at two levels: ex vivo by analysing the presence of PR3 on the plasma membrane of PMN from patients with ANCA-associated vasculitis, and in vitro by stimulation of PMN using different cytokines, including recombinant tumour necrosis factor-alpha (rhTNF-alpha) and two forms of IL-8 (produced by monocytic and endothelial cells). Using immunocytochemical staining techniques (FACS and immunoelectronmicroscopy) PR3 has been detected on the plasma membrane of PMN from patients with active ANCA-associated vasculitis. However, this phenomenon is also seen in patients with sepsis who do not have ANCA. In addition, TNF-alpha and both forms of IL-8 act synergistically and induce a translocation of PR3 from the intragranular loci to the cell surface of PMN. These results provide strong evidence for the hypothesis that ANCA are directly pathogenic by binding to PR3 which is expressed on the cell surface of primed/activated PMN.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1994

A functional integrin ligand on the surface of platelets: intercellular adhesion molecule-2.

Activated platelets express P-selectin and release leukocyte chemoattractants; however, they have not been known to express integrin ligands important in the stabilization of leukocyte interactions with the vasculature. We now demonstrate the presence of intercellular adhesion molecular-2 (ICAM-2) (CD102), and lack of expression of other beta 2-integrin ligands, ICAM-1 (CD54) and ICAM-3 (CD50), on the surface of resting and stimulated platelets. ICAM-2 isolated from platelets migrates as a band of 59,000 M(r) in reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Staining of bone marrow aspirates with anti-ICAM-2 mAb demonstrates strong reactivity to megakaryocytes. Using frozen thin sections and immunogold labeling, the antigen was shown to be present on the plasma membrane and surface-connected canalicular system of resting platelets. The average number of ICAM-2 molecules per platelet is 3,000 +/- 230 and does not change after activation. In adhesion assays, resting and stimulated platelets were capable of binding through ICAM-2 to purified leukocyte function-associated antigen-1. Activation of T lymphocytes with PMA stimulated binding to platelets that was Mg2+ dependent and could be specifically inhibited by mAbs to either ICAM-2 or leukocyte function-associated antigen-1. ICAM-2 is the only known beta 2-integrin ligand present on platelets, suggesting that it may play an important role in leukocyte-platelet interactions in inflammation and thrombosis.

Antibodies, Monoclonal↗
PubMed1994

Granulophysin is located in the membrane of azurophilic granules in human neutrophils and mobilizes to the plasma membrane following cell stimulation.

Granulophysin, a protein described in platelet dense granule membranes, has been shown to be similar or identical to CD63, a lysosomal membrane protein. We have previously shown granulophysin to be present in neutrophils using immunofluorescence. We now localize granulophysin to the neutrophil azurophilic granules by fine structural immunocytochemistry. Granulophysin expression on the surface membrane of the neutrophil is increased following stimulation of the cells, demonstrated by flow cytometry and fine structural immunocytochemistry. A similar pattern is shown for an anti-CD63 antibody. Incubation of activated neutrophils with D545, a monoclonal antibody to granulophysin, blocks subsequent binding of anti-CD63 antibodies to the cell surface, and anti-CD63 antibodies prevent subsequent binding of D545 as assessed by flow cytometry and immunoblotting. Our results support the homology of CD63 and granulophysin previously demonstrated in platelets and confirm CD63 as an activation marker in neutrophils and the first azurophilic granule membrane marker of neutrophils.

Antigens, CD↗
PubMed1993

Structural and functional heterogeneity among peroxidase-negative granules in human neutrophils: identification of a distinct gelatinase-containing granule subset by combined immunocytochemistry and subcellular fractionation.

The existence of separate gelatinase granules in human neutrophils has been a matter of debate in recent years. We have demonstrated that the 135-kD form of neutrophil gelatinase is a complex of 92-kD gelatinase and a novel 25-kD protein termed neutrophil gelatinase-associated lipocalin (NGAL) that, in addition to being complexed with part of the gelatinase, is localized in free form in peroxidase-negative specific granules. Because this association was not appreciated in earlier studies, we decided to reassess the ultrastructural localization of gelatinase using specific antibodies without immunoreactivity towards NGAL. Double-labeling immunogold electron microscopy was performed on frozen thin sections of human neutrophils. Twenty-four percent of all peroxidase-negative granules were labeled with antigelatinase antibody, but not with antilactoferrin antibody. These granules are defined as gelatinase granules. Sixteen percent reacted with antilactoferrin antibody but not with antigelatinase antibody. The rest (60%) reacted with both antibodies. All granules labeling for lactoferrin are defined as specific granules. Gelatinase granules were observed as round and oval forms of considerably smaller size than specific granules, and were less electron dense. Isolated granules obtained by subcellular fractionation were also examined by immunoelectron microscopy. This demonstrated that peroxidase-negative granules comprise a continuum from the most dense granules that contain lactoferrin but no gelatinase to the lightest that contain gelatinase but no lactoferrin. Thus, gelatinase granules do exist as a subpopulation of peroxidase-negative granules and may allow for exocytosis of gelatinase during neutrophil diapedesis without substantial mobilization of other peroxidase-negative granules, ie, specific granules.

Cytoplasmic Granules↗
PubMed1993

Endocytosis of fibrinogen into megakaryocyte and platelet alpha-granules is mediated by alpha IIb beta 3 (glycoprotein IIb-IIIa)

Recently, we showed that platelet alpha-granule fibrinogen is derived entirely from endocytic uptake and not from megakaryocyte synthesis, as previously thought. In this present report, we identify the receptor that mediates endocytosis. We have found that barbourin, a unique disintegrin that is a specific antagonist of alpha IIb beta 3, inhibits the endocytic uptake of fibrinogen into alpha-granules. Continuous intravenous infusion of barbourin (200 micrograms/h) into guinea pigs blocked collagen-induced platelet aggregation as well as endocytosis of biotinylated fibrinogen into megakaryocytes; however, endocytosis of biotinylated albumin by megakaryocytes was not affected. Thus, we have shown that endocytosis of fibrinogen into megakaryocyte and platelet alpha-granules is receptor-mediated, and that alpha IIb beta 3 is the primary receptor.

Animals↗
PubMed1993

Membrane surface proteinase 3 expression and intracytoplasmic immunoglobulin on neutrophils from patients with ANCA-associated vasculitides.

We studied the presence of proteinase 3 (PR3), myeloperoxidase (MPO) and elastase (HLE) on the plasma membrane of neutrophils in patients with biopsy-proven Wegener's disease (WG), pANCA-positive vasculitis, control patients (SLE, rheumatoid arthritis, ankylosing spondylitis), sepsis patients and healthy donors. We found an overexpression of PR3 on the cell surface of neutrophils in WG, ANCA-associated vasculitis and during infection (sepsis). Thus PR3 becomes accessible to ANCA. Furthermore we detected intracytoplasmic IgG antibodies in PMN from patients with WG by immunoelectron microscopy and direct immunofluorescence. Our findings support the pathophysiological role of ANCA.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1993

Human neutrophil granules and secretory vesicles.

The traditional classification of neutrophil granules as peroxidase-positive (azurophil, or primary) and peroxidase-negative (specific or secondary) has proven to be too simple to explain the differential exocytosis of granule proteins and incorporation of granule membrane into the plasma membrane which is an important aspect of neutrophil activation. Combined subcellular fractionation and immunoelectron microscopy has revealed heterogeneity among both peroxidase-positive and peroxidase-negative granules with regard to their content, mobilization and time of formation. Peroxidase-negative granules may be classified according to their content of lactoferrin and gelatinase: 15% of peroxidase-negative granules contain lactoferrin, but no gelatinase. 60% contain both lactoferrin and gelatinase. The term specific or secondary granule should be reserved for these two subsets. In addition, 25% of peroxidase-negative granules contain gelatinase but no lactoferrin. These should be termed gelatinase granules or tertiary granules. Gelatinase granules are formed later than specific granules and mobilized more readily. In addition, a distinct, highly mobilizable intracellular compartment, the secretory vesicle, has now been recognized as an important store of surface membrane-bound receptors. This compartment is formed in band cells and segmented cells by endocytosis. This heterogeneity among the neutrophil granules is of functional significance, and may also be reflected in the dysmaturation which is an important feature of myeloproliferative and myelodysplastic disorders.

Calcium↗
PubMed1993

Kistrin, an integrin antagonist, blocks endocytosis of fibrinogen into guinea pig megakaryocyte and platelet alpha-granules.

Recent data indicate that megakaryocyte/platelet alpha-granule fibrinogen is endocytosed from plasma. Because fibrinogen is the major platelet protein present in high concentrations in alpha-granules, fibrinogen uptake into alpha-granules may occur via specific receptors. In that cells of the megakaryocyte/platelet lineage contain two integrins--alpha IIb beta 3 (GP IIb-IIIa) and the vitronectin receptor (alpha v beta 3)--that can bind fibrinogen, one or both of these receptors may mediate the endocytic uptake of fibrinogen. To test this hypothesis, we examined the effect of Kistrin, an RGD-containing protein purified from the venom of Agkistrodon rhodostoma that inhibits fibrinogen binding to human platelet receptors, on endocytosis of fibrinogen by megakaryocytes and platelets. Continuous intravenous infusion of kistrin into guinea pigs (200 micrograms/h) over a 24-h period inhibited collagen-induced platelet aggregation. When biotinylated fibrinogen was injected intravenously into animals receiving Kistrin, megakaryocytes failed to endocytose the labeled fibrinogen. Endocytosis of fibrinogen into platelets was also inhibited in these animals. In contrast, platelets and megakaryocytes obtained from sham-infused control animals contained the injected biotinylated fibrinogen. We conclude that, in addition to the well-known extracellular function of cell adhesion, integrins can also act as receptors that mediate endocytosis of exogenous proteins and incorporate them into regulated secretory granules.

Animals↗
PubMed1993

Multimerin is found in the alpha-granules of resting platelets and is synthesized by a megakaryocytic cell line.

In this report, we describe the intracellular localization of multimerin in platelets and its biosynthesis by Dami cells, a megakaryocytic cell line. Immunoelectron microscopy was used to examine frozen thin sections of resting and activated platelets. Multimerin was localized within the platelet alpha-granule in an eccentric position. Within activated platelets, multimerin was found in the surface-connected open cannalicular system and on the external plasma membrane. Light microscopic immunocytochemistry demonstrated multimerin in normal megakaryocytes and in Dami cells after stimulation with PMA. Confirmation of multimerin biosynthesis by Dami cells was obtained by metabolic labeling studies. Both platelet and Dami cell multimerin demonstrated several subunit sizes on reduced SDS-PAGE. However, peptide mapping confirmed structural homology between the different multimerin subunits. Glycosidase digestion demonstrated that multimerin is heavily glycosylated with mainly complex, N-linked carbohydrate. In contrast to the multimerin isolated from platelets, cultured Dami cells secreted mainly smaller multimers of the protein. Biosynthesis of multimerin by a megakaryocytic cell line supports endogenous biosynthesis by megakaryocytes as the origin of this platelet alpha-granule protein.

Blood Platelets↗
PubMed1992

Platelet dense granule membranes contain both granulophysin and P-selectin (GMP-140).

We recently reported the characterization of a platelet granule membrane protein of molecular weight (mol wt) 40,000 called granulophysin (Gerrard et al: Blood 77:101, 1991), identified by a monoclonal antibody (MoAb D545) raised to purified dense granule membranes. Using immunoelectron-microscopic techniques on frozen thin sections, this protein was localized in resting and thrombin-stimulated platelets. In resting platelets, labeled with antigranulophysin antibodies and immunogold probes, label was localized to the membranes of one or two clear granules per platelet thin section. D545 also labeled dense granules in permeabilized whole platelets and isolated dense granule preparations examined by whole-mount techniques. Expression of granulophysin on the platelet surface paralleled dense granule secretion as measured by 14C-serotonin release under conditions in which lysosomal granule release, as measured by beta-glucuronidase secretion, was less than 5%. After thrombin stimulation, both the surface-connected canalicular system and the plasma membrane were labeled, demonstrating redistribution of granulophysin associated with degranulation. Double labeling experiments with D545 and antibodies to the alpha-granule membrane protein, P-selectin, demonstrated labeling of both P-selectin and granulophysin on dense granule membranes. Distribution of both proteins on the plasma membrane after platelet stimulation was similar. The results demonstrate that granulophysin is localized to the dense granules of platelets and is redistributed to the plasma membrane after platelet activation.

Antibodies, Monoclonal↗
PubMed1992

Cytoplasmic domain of P-selectin (CD62) contains the signal for sorting into the regulated secretory pathway.

P-selectin (CD62), formerly called GMP-140 or PADGEM, is a membrane protein located in secretory storage granules of platelets and endothelial cells. To study the mechanisms responsible for the targeting of P-selectin to storage granules, we transfected its cDNA into COS-7 and CHO-K1 cells, which lack a regulated exocytic pathway, or into AtT20 cells, which are capable of regulated secretion. P-selectin was expressed on the plasma membrane of COS-7 and CHO-K1 cells but was concentrated in storage granules of AtT20 cells. Immunogold electron microscopy indicated that the electron-dense granules containing P-selectin in AtT20 cells also stored the endogenous soluble hormone ACTH. Activation of AtT20 cells with 8-Br-cAMP increased the surface expression of P-selectin, consistent with agonist-induced fusion of granule membranes with the plasma membrane. Deletion of the last 23 amino acids of the 35-residue cytoplasmic domain resulted in delivery of P-selectin to the plasma membrane of AtT20 cells. Replacement of the cytoplasmic tail of tissue factor, a plasma membrane protein, with the cytoplasmic domain of P-selectin redirected the chimeric molecule to granules. We conclude that the cytoplasmic domain of P-selectin is both necessary and sufficient for sorting of membrane proteins into the regulated pathway of secretion.

Adrenocorticotropic Hormone↗
PubMed1991

Decreased content and surface expression of alpha-granule membrane protein GMP-140 in one of two types of platelet alpha delta storage pool deficiency.

To determine whether alpha-granule membranes are present in platelets of patients with storage pool deficiencies of both alpha and dense granules (alpha delta-SPD), we examined the content and surface expression of the alpha-granule membrane protein GMP-140 in one patient (J.C.) with a severe alpha-granule deficiency and in three members of a family (family C) with milder alpha-granule deficiencies. Surface expression of GMP-140 in stimulated platelets, assessed by flow cytometric measurements of the binding of two anti-GMP-140 monoclonal antibodies, was 24-38% of normal values in platelets from patient J.C., vs. 60-95% of normal values in family C. Total platelet content of GMP-140, determined in platelet lysates by antigen-capture ELISA, was 49% of normal in patient J.C., but normal in the members of family C. Platelets of patient J.C. were found to be heterogeneous with respect to GMP-140 content and surface expression by both flow cytometry and immunogold electron microscopy. Approximately 80% of her platelets expressed little or no GMP-140 after stimulation, whereas the remaining 20% expressed normal amounts of GMP-140 and showed extensive immunogold labeling of typical alpha-granules and clear vacuoles. No such heterogeneity was found in platelets from family C. These findings in the severe alpha delta-SPD patient are in clear contrast to the observations of normal GMP-140 content in the three other alpha delta-SPD patients, and in patients with the gray platelet syndrome, reported previously by others. These results illustrate the phenotypic heterogeneity of alpha-granule deficiencies in human platelets, and suggest that a defect in granule formation in the megakaryocytes may account for the alpha-granule defect in at least one form of alpha delta-SPD.

Adult↗
PubMed1990

Monoclonal antibodies bound to subunits of the integrin GPIIb-IIIa are internalized and interfere with filopodia formation and platelet aggregation.

The monoclonal antibodies Tab and AP3 are directed, respectively, against GPIIb and GPIIIa, the subunits of the platelet fibrinogen receptor. When added together to platelets, these antibodies prevent adenosine diphosphate (ADP)-induced platelet aggregation, despite normal fibrinogen binding (Newman et al, Blood 69:668, 1987). To explore the cellular requirements of aggregation after fibrinogen binding, we used several techniques to study platelets treated with Tab and AP3, then stimulated with ADP. We used scanning and transmission electron microscopy to evaluate platelet morphology, immunolabel-surface replication to determine whether individual GPIIb-IIIa complexes clustered, immunocytochemistry on frozen thin sections to study the subcellular distribution of the integrin GPIIb-IIIa and fibrinogen, and biochemical methods to assess the activation of the platelet cytoskeleton. We found that the treated cells had short, blunted projections instead of normal filopodia. Other morphologic abnormalities, apparent in thin section, were aberrantly placed alpha-granules and microtubules, and a prominent, worm-like, fibrinogen-filled surface-connected canalicular system. Biochemical analysis suggested that such platelets undergo massive actomyosin-controlled membrane flow, which serves to sequester GPIIb-IIIa and makes the platelets refractory to aggregation. We conclude that aggregation requires the formation of long, slender filopodia, probably directed by cytoskeletal rearrangements after activation, and that the transmembrane GPIIb-IIIa complex may play a role in signaling these events.

Adenosine Diphosphate↗
PubMed1990

Ultrastructural localization of a macrophage-restricted sialic acid binding hemagglutinin, SER, in macrophage-hematopoietic cell clusters.

Resident bone marrow macrophages in hematopoietic clusters have previously been shown to express a novel lectin-like sheep erythrocyte receptor, SER, which mediates binding of unopsonized sheep erythrocytes via recognition of sialylated glycoconjugates and may interact with sialylated ligands on murine bone marrow cells. In this study, the distribution of SER on macrophages within hematopoietic clusters was localized by a monoclonal antibody, SER-4, by immunofluorescence and immunoelectron microscopy. SER was found to be diffusely localized at the contact zones between macrophages and erythroblasts, whereas the receptor was highly concentrated at the contacts between macrophages and developing myelomonocytic cells. These data suggest that SER on resident bone marrow macrophages interacts differentially with sialylated ligands on developing myeloid cells and that this may influence their development.

Animals↗
PubMed1990

Platelet alpha-granule fibrinogen, albumin, and immunoglobulin G are not synthesized by rat and mouse megakaryocytes.

It has been assumed that endogenous synthesis by the platelet precursor cell, the bone marrow megakaryocyte, is the major source of platelet alpha-granule protein. To test this hypothesis, we used mRNA phenotyping to detect in megakaryocytes the presence of mRNA transcripts specific for various proteins. Our results indicate that megakaryocytes synthesize platelet factor 4, a protein relatively specific for platelets, but do not express mRNA transcripts for the fibrinogen, albumin, or IgG found in alpha-granules. We have previously shown that megakaryocytes endocytose circulating proteins, including fibrinogen, albumin, and IgG, and incorporate them into alpha-granules. Thus, platelets appear to contain a unique type of secretory granule whose contents originate by both endogenous synthesis and endocytosis from plasma. Under basal conditions, the source of alpha-granule fibrinogen is plasma.

Animals↗