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Biomedical subjects

T S Edgington

Publications and source records attributed to T S Edgington.

At least 145 records · Page 8Linked to original sources
PubMed1982

Immunochemical heterogeneity of human plasma apolipoprotein B. II. Expression of apolipoprotein B epitopes on native lipoproteins.

Eleven hybridoma antibodies specific for apoprotein B were used to examine the expression of apoprotein B epitopes on native plasma lipoproteins using fluid phase radioimmunoassays. Heterogeneity of apoprotein B in low density lipoprotein (LDL) of density 1.019-1.063 g/ml was indicated by maximum binding of radioiodinated LDL in the presence of excess antibody that ranged from 45 to 100%. Affinity constants for LDL ranged from 0.29-3.0 X 10(9) M-1. Each of the 11 antibodies recognized apoprotein B epitopes that were expressed by very low, intermediate, and low density lipoproteins, VLDL, IDL, and LDL, respectively, since at high concentrations, each could fully displace the binding of radioiodinated LDL. In contrast, these same apoprotein B epitopes were not present on high density lipoproteins. Logit transformation analysis of competitive inhibition titrations demonstrated at least three patterns of epitope expression. The first pattern, identified by five of the antibodies, was characterized by indistinguishable expression of each of the apoprotein B epitopes on VLDL, IDL, and LDL. The second pattern, identified by three antibodies, was characterized by identical expression of the apoprotein B epitopes on VLDL and IDL, but of differing affinities than the related epitope on LDL. Three antibodies identified a third pattern of epitope expression which was was characterized by identical expression on IDL and LDL, but with differing affinities for the antibodies than the same epitopes on VLDL. These observations suggest that the organization of apoprotein B in VLDL, IDL, and LDL is similar, but not identical.

Animals↗
PubMed1982

Murine lymphoid procoagulant activity induced by bacterial lipopolysaccharide and immune complexes is a monocyte prothrombinase.

Murine lymphoid cells respond rapidly to bacterial lipopolysaccharide or antigen-antibody complexes to initiate or accelerate the blood coagulation pathways. The monocyte or macrophage has been identified as the cellular source, although lymphocyte collaboration is required for the rapid induction of the procoagulant response. This procoagulant activity is identified in the present study as a direct prothrombin activator, i.e., a prothrombinase. Studies with plasmas deficient in single coagulation factors demonstrate that the induced murine procoagulant activity effector molecule does not require factors XII, VIII, VII, X, or V, but does require prothrombin to transform fibrinogen to fibrin. This enzyme(s) produces limited proteolysis of prothrombin to yield thrombin or thrombinlike products that are functionally capable of converting fibrinogen to fibrin. The prothrombinase is undetectable in freshly isolated Murine lymphoid cells respond rapidly to bacterial lipopolysaccharide or antigen-antibody complexes to initiate or accelerate the blood coagulation pathways. The monocyte or macrophage has been identified as the cellular source, although lymphocyte collaboration is required for the rapid induction of the procoagulant response. This procoagulant activity is identified in the present study as a direct prothrombin activator, i.e., a prothrombinase. Studies with plasmas deficient in single coagulation factors demonstrate that the induced murine procoagulant activity effector molecule does not require factors XII, VIII, VII, X, or V, but does require prothrombin to transform fibrinogen to fibrin. This enzyme(s) produces limited proteolysis of prothrombin to yield thrombin or thrombinlike products that are functionally capable of converting fibrinogen to fibrin. The prothrombinase is undetectable in freshly isolated

Animals↗
PubMed1981

Issues in immunologically-mediated hepatic injury.

Chronic infection with hepatitis B virus is widespread, and there are other forms of chronic hepatitis in which the host's immune response is pathogenic. A conference study group report assessed faulty immune effector mechanisms. The immune pathways considered were effector cell recruitment and cytolytic mechanisms, including hepatocyte killing by antigen-specific T lymphocytes, non-antigen-specific cells (K and NK cells, macrophages), and antibody plus complement. Also considered were "modulating" effects of surface-located antibody which could result in reduction of killing by T cells of virus-infected hepatocytes which could facilitate chronicity. Evidence for participation of these immune effector processes has not yet been convincing in human chronic hepatitis. Future research must be directed to defining the type and specificity of cytolytic effector systems and circumstances under which host antibody diminishes or augments the activity of such systems, delineating putative auto-antigens, and developing suitable animals models.

Animals↗
PubMed1981

Induction of monocyte procoagulant activity by murine hepatitis virus type 3 parallels disease susceptibility in mice.

The in vitro induction of procoagulant activity (PCA) in murine peripheral blood mononuclear cells (PBM) by murine hepatitis virus type 3 (MHV-3) correlates with the disease susceptibility in three strains of mice. PBM from BALB/c mice, a strain in which MHV-3 infection results in fatal acute fulminant hepatitis, responds to the virus with a robust PCA response, whereas PBM from C3H/St mice, a strain which develops mild acute hepatitis followed by chronic hepatitis, only exhibit a modest PCA response. In contrast, PBM from A/J mice, a strain fully resistant to MHV-3, generate no increase in PCA above control levels. The induction phase of MHV-3 PCA is rapid, with an increase within 1-1.5 h, with maximum activity at 18h, and it precedes MHV-3 replication in either 17 CL1 cells, a fully permissive cell line, or in monocytes from these strains of mice. The PCA response of BALB/c PBM exceeds the response to any other known stimulus. No induction occurs upon direct stimulation of monocytes by MHV-3, but in the presence of lymphocyte collaboration, the PCA response is observed first at a lymphocyte:monocyte ratio of 2:1 and reaches a maximum as the lymphocyte:monocyte ratio approaches 4:1. This response appears to provide a functional marker for susceptibility to MHV-3 infection in inbred strains of mice and could be important in the pathogenesis of MHV-3-induced disease.

Animals↗
PubMed1981

Immune complex-induced human monocyte procoagulant activity. I. a rapid unidirectional lymphocyte-instructed pathway.

It has previously been described that soluble antigen:antibody complexes in antigen excess can induce an increase in the procoagulant activity of human peripheral blood mononuclear cells. It has been proposed that this response may explain the presence of fibrin in immune complex-mediated tissue lesions. In the present study we define cellular participants and their roles in the procoagulant response to soluble immune complexes. Monocytes were shown by cell fractionation and by a direct cytologic assay to be the cell of origin of the procoagulant activity; and virtually all monocytes were able to participate in the response. Monocytes, however, required the presence of lymphocytes to respond. The procoagulant response required cell cooperation, and this collaborative interaction between lymphocytes and monocytes appeared to be unidirectional. Lymphocytes once triggered by immune complexes induced monocytes to synthesize the procoagulant product. Intact viable lymphocytes were required to present instructions to monocytes; no soluble mediator could be found to subserve this function. Indeed, all that appeared necessary to induce monocytes to produce procoagulant activity was an encounter with lymphocytes that had previously been in contact with soluble immune complexes. The optimum cellular ratio for this interaction was four lymphocytes per monocyte, about half the ratio in peripheral blood. The procoagulant response was rapid, reaching a maximum within 6 h after exposure to antigen:antibody complexes. The procoagulant activity was consistent with tissue factor because Factors VII and X and prothrombin were required for clotting of fibrinogen. WE propose that this pathway differs from a number of others involving cells of the immune system. Elucidation of the pathway may clarify the role of this lymphocyte-instructed monocyte response in the Shwartzman phenomenon and other thrombohemorrhagic events associated with immune cell function and the formation of immune complexes.

Animals↗
PubMed1981

Immunochemical mapping of the conformation of human fibrinogen. The gamma 95-264 segment in inaccessible to antibody in native fibrinogen but progressively exposed by plasmic cleavage.

The accessibility of the gamma 95-264 sequence to specific antibody probes in the native fibrinogen molecule and its plasmic cleavage fragments have been investigated. The gamma 95-264 segment was generated by cyanogen bromide cleavage of the gamma chain and isolated by gel filtration and ion exchange chromatography. Rabbit antisera to this peptide and to gamma chain recognized at least five antigenic loci uniformly distributed throughout this segment. In primary binding assays, antibodies to gamma 95-264 bound gamma 95-264, free gamma chain, and fibrinogen fragment D, but not native fibrinogen. Also, gamma 95-264 was bound by antibodies to gamma chain and fibrinogen fragment D, but not by antibodies generated to native fibrinogen. Thus, the gamma 95-264 sequence was not accessible to antibody in the native structure. In competitive equilibrium radioimmunoassays, neither native fibrinogen nor highly soluble fibrinogen fraction I-9 inhibited the binding of gamma 95-264 by its antiserum or anti-gamma chain. With plasmic cleavage, however, the gamma 95-264 sequence became accessible to antibody and the series of fragments D greater than Y greater than D:E = X describes the relative reactivity of the gamma chain sequence in fibrinogen degradation products. Differential expression of gamma 95-264 antigenic loci was also observed with D fragments differing in molecular weight. Plasmic cleavage of cross-linked and noncross-linked fibrin generated D fragments which did not express gamma 95-264 as well as fibrinogen D derivatives, indicating that the D domains of fibrinogen and fibrin are immunochemically distinguishable. These findings indicate that the central segment of the gamma chain is inaccessible to antibody in native fibrinogen, but that proper surface orientation is achieved upon plasmic degradation.

Antibodies↗
PubMed1981

Characteristics of membrane and cytosol forms of the mammary tumor glycoprotein molecule MTGP in human breast carcinoma cell cultures and tumors.

The presence, concentration and selected molecular characteristics of the human mammary carcinoma glycoprotein molecule set MTGP, a trace and apparently tumor-specific molecule, were examined in fifteen cell cultures established from mammary carcinomas, tissue from seven mammary carcinomas and control cultures. Both cytosol and membrane-associated forms of MTGP were analyzed, and each was phenotyped by reference to isoelectric point and buoyant density. All cells or tissues of mammary carcinoma origin contained membrane MTGP, whereas cytosol MTGP was undetectable in cell cultures from half of the mammary carcinomas. Neither membrane nor cytosol MTGP were detectable in cells other than mammary carcinomas. Cytosol MTGP could be assigned to three groups by reference to presence, isoelectric point and buoyant density. Membrane MTGP also exhibited heterogeneity between different tumors and could be assigned to three groups by isoelectric point and buoyant density. Each form of MTGP was homogeneous for a given single tumor or cell culture and retained its phenotypic features with passage and cloning. Four general types of MTGP are proposed, through there may be additional fine heterogeneity that cannot be further resolved at this time. These data provide an initial characterization of the membrane form of MTGP and an integrated characterization that is consistent with the concept that tumor-specific antigens may possess both constant regions by reference to antigens recognized by the antisera and variable structure by reference to physicochemical characteristics.

Antigens, Neoplasm↗
PubMed1981

An inhibitor of plasminogen activator in rabbit endothelial cells.

The antifibrinolytic activity of cytosols obtained from cultured rabbit endothelial cells was studied to determine whether it resulted from the presence of an antiplasmin or an antiactivator. These cytosol preparations inhibited the fibrinolytic activity initiated by some plasminogen activators (e.g. urokinase, rabbit endothelial cell activator), but not others (e.g. activators associated with bovine endothelial cells and Rous sarcoma virus-infected chick embryo fibroblasts), suggesting that inhibition occurred at the level of plasmin formation, not plasmin activity. The fibrinolytic activity of plasmin itself was unaffected by concentrations of cytosol that completely blocked urokinase-mediated fibrinolysis consistent with this conclusion. In addition, the ability of urokinase to cleave 125I-plasminogen into its characteristic activation fragments was inhibited by cytosol in a dose-dependent manner. When urokinase was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, two peaks of activity were detected, corresponding to Mr = 55,000 and 32,000. Urokinase preincubated with cytosol and analyzed in a similar manner demonstrated no activity in any portion of the gel, suggesting that its ability to function as a plasminogen activator was irreversibly lost following its interaction with cytosol. These results indicate that the antifibrinolytic activity of rabbit endothelial cells results from the presence of a molecule or molecules with antiactivator activity. The cellular location and unusual degree of specificity distinguish the endothelial cell inhibitor(s) from antifibrinolytic agents observed in other cells and in plasma and platelets.

Animals↗
PubMed1981

Plasma lipoprotein induction and suppression of the generation of cellular procoagulant activity in vitro.

Isolated human plasma very low density, intermediate density, and high density lipo-proteins at physiologic concentrations have been demonstrated in the preceding report to induce significant increases in the procoagulant activity of human peripheral blood mononuclear cells in vitro, whereas low density lipoprotein did not. The monocyte was identified in this study by cellular fractionation and by direct cytologic assays as the source of this inducible activity, thus identifying the procoagulant activity as a monokine. The generation of these lipoprotein-induced procoagulant monokines was entirely dependent upon the presence of lymphocytes. Isolated lymphocytes that had been exposed to the stimulatory lipoproteins could induce monocytes to produce the procoagulant activity, whereas neither the culture medium from lipoprotein-stimulated lymphocytes, homogenates of lymphocytes, nor other cells such as platelets could substitute for this requirement. The interaction of the stimulatory lipoproteins with lymphocytes was rapid, reaching completion within 30 min, and was equally effective at either 4 degrees or 37 degrees C. Low density lipoprotein did not stimulate lymphocytes to induce monocyte procoagulant activity, but did actively suppress the production of the procoagulant monokines induced by each of the stimulatory lipoproteins, as well as bacterial lipopolysaccharide. The monocyte was identified as the cell sensitive to low density lipoprotein suppression, and no suppression of lymphocyte triggering was observed. These observations on the interaction of plasma lipoproteins with lymphocytes and monocytes in vitro introduce two new regulatory events by which plasma lipoproteins influence the function of cells, and define a regulatory network by which certain lipoprotein classes trigger lymphocytes, which can in turn induce monocytes to express procoagulant activity. Only this latter phase is subject to lipoprotein suppression by physiologic concentrations of low density lipoprotein.

Blood Coagulation Factors↗
PubMed1981

Plasma lipoprotein induction and suppression of the generation of cellular procoagulant activity in vitro: two procoagulant activities are produced by peripheral blood mononuclear cells.

In the process of analyzing the effects of lipoproteins on functions of lymphoid cells, it was observed that physiological concentrations of isolated human plasma lipoproteins possess varying capacities to rapidly enhance the expression of procoagulant activity of human peripheral blood mononuclear cells in vitro. In a strict dose-dependent fashion, very low density lipoprotein, intermediate density lipoprotein, and high density lipoprotein enhanced both the surface expression by viable cells and the total cellular content of procoagulant activity during a 6-h incubation. Very low density lipoprotein induced a maximal 6.7-fold increase in the expression of a thromboplastin activity, which was consistent with tissue factor, in that it was dependent on Factors VII, X, and II. Both intermediate density lipoprotein and high density lipoprotein induced approximately a 12-fold increase of a different procoagulant activity which appears to be a direct prothrombin activator. This prothrombinase was calcium dependent and was inhibited by 2.5 mM diisopropylfluorophosphate, but was not neutralized by anti-Factor X antibodies or by inhibitors of Factor Xa. In contrast to the other lipoprotein density classes, low density lipoprotein did not stimulate procoagulant activity, but instead actively suppressed the generation of the two procoagulant activities induced by the stimulatory lipoproteins. Suppression by low density lipoprotein was clearly evident at molar ratios of low density lipoprotein to stimulatory lipoproteins of 1:3 or less. Reconstitution of all lipoproteins to physiological concentrations was not stimulatory as a consequence of the suppressive effects of low density lipoprotein. These data indicate that isolated plasma lipoproteins are capable of regulating the expression of two different procoagulant activities of peripheral blood mononuclear cells in vitro. The possibility that these interactions may be implicated in the association between certain types of hyperlipoproteinemias and thromboembolic disease merits study.

Blood Coagulation Factors↗
PubMed1981

The biologic activity of the immunoregulatory lipoprotein, LDL-In is independent of its free fatty acid content.

The immunoregulatory normal plasma lipoprotein subclass, termed LDL-In, suppresses a number of immune responses in vitro including peripheral blood lymphocyte phytohemagglutinin-stimulated 3H-thymidine uptake, pokeweed mitogen-driven immunoglobulin synthesis, and the generation of cytolytic T cells. In vivo parallels have also been demonstrated. Plasma lipoproteins represent noncovalent complexes of lipid and apolipoprotein chains. Since free fatty acids have been demonstrated to suppress certain lymphocyte responses including mitogen-stimulated 3H-thymidine uptake, we have examined the hypothesis that the free fatty acids associated with LDL-In particles are the biologically active constituents. However, the dose-dependence and the kinetics of LDL-In-mediated suppression were distinctly different from those observed for a number of free fatty acids. In addition, when greater than 92% of the endogenous free fatty acids of LDL-In were removed by incubation in the presence of delipidated albumin, no differences were observed between this free fatty acid depleted LDL-In and native LDL-In with respect to suppressive activity for lymphocyte stimulation or binding to the lymphocyte LDL-In receptor. These observations indicate that the interaction of the LDL-In particle with the lymphocyte receptor and the suppression of lymphocyte function are independent of the free fatty acid content of this bioregulatory lipoprotein, thus focusing attention on the apolipoprotein chains or the phospholipids and glycolipids of this minor plasma lipoprotein.

Adsorption↗
PubMed1981

Lymphocyte collaboration is required for induction of murine monocyte procoagulant activity by immune complexes.

Both aggregated IgG and soluble immune complexes composed of human serum albumin and specific antibody at a 4:1 ratio were demonstrated to rapidly induce an increase in procoagulant activity (PCA) of murine peripheral blood mononuclear cells. Direct cytologic assays as well as fractionation of cells by adherence to plastic established the monocyte as the cell producing PCA, and demonstrated further that almost all monocytes, rather than a subpopulation, participated in the response. Monocytes that were depleted of lymphocytes did not respond to these stimuli with production of PCA; that is, induction of monocyte PCA was observed only when stimulation was performed in the presence of lymphocytes. Induction was equally efficient when only the lymphocyte was stimulated by aggregated IgG or soluble immune complexes, washed free of unbound stimulus, and added to monocytes. This suggests a unidirectional pathway by which the stimulus triggers lymphocytes after which there is direct lymphocyte-mediated induction of monocytes to produce PCA. Evidence for participation of soluble lymphocyte products was not obtained, and it is suggested that this series of events may be mediated by direct lymphocyte contact with responding monocytes. The role of this pathway in the genesis of immunologically initiated tissue lesions is discussed.

Animals↗