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PubMed1981

Studies on cell adhesion and recognition. II. The kinetics of cell adhesion and cell spreading on surfaces coated with carbohydrate-reactive proteins (glycosidases and lectins) and fibronectin.

The kinetics of cell attachment and cell spreading on the coated surfaces of two classes of carbohydrate-reactive proteins, enzymes and lectins, have been compared with those on fibronectin-coated surfaces with the following results: (a) A remarkable similarity between the kinetics of cell attachment to fibronectin-coated and glycosidase-coated surfaces was found. In contrast, cell attachment kinetics induced by lectin- and galactose oxidase-coated surfaces, in general, were strikingly different from those on fibronectin and glycosidase surfaces. The distinction between fibronectin- or glycosidase- and lectin- or galactose oxidase (an enzyme with lectin-type characteristics)-coated surfaces was further supported by the finding that cytochalasin B and EDTA inhibited cell attachment to fibronectin- and glycosidase-coated surfaces but not lectin-coated surfaces. (b) Fibronectin, if labeled and added to a cell suspension, showed only low or negligible interaction with the cell surface. However, fibronectin absorbed on plastic surfaces showed a high cell-attaching activity. It is assumed that fibronectin coated on plastic surfaces may form polyvalent attachment sites in contrast to its lower valency in aqueous solution. (c) Various inhibitors of cell attachment to both fibronectin-, galactose oxidase-, and lectin-coated surfaces were effective only during the first few minutes of the adhesion assay, after which time the attached cells became insensitive to the inhibitors. It is suggested that the initial specific recognition on either lectin-type or fibronectin-type surfaces is followed by an active cell-dependent attachment process. The primary role of the adhesion surface is to stimulate the cell-dependent attachment response. (d) Cells attached on tetravalent concanavalin A (Con A) spread very rapidly and quantitatively, whereas divalent succinyl Con A and monovalent Con A were effective stimulators of cell attachment but not cell spreading. Cross-linking of succinyl Con A restored the cell spreading activity. Tetravalent Con A surfaces specifically bind soluble glycoproteins, whereas succinyl Con A has a greatly reduced ability to bind the same glycoproteins. These results suggest that cross-linking of cell surface glycoproteins by the multivalent adhesive surface may trigger the cellular reaction leading to cell spreading.

Animals↗
PubMed1984

Substrate adhesion of rat hepatocytes: on the mechanism of attachment to fibronectin.

We examined the mechanisms of cell attachment to fibronectin-coated substrates. Inhibition of cell attachment was obtained by species-specific antifibronectin antibodies, which presumably recognize a distinct antigenic structure in the protein located at, or in the immediate vicinity of, the cell-binding site. The inhibiting antibodies could be adsorbed on a column of Sepharose substituted with plasma fibronectin. The initial phase of cell attachment was also inhibited by addition of soluble fibronectin to the incubation medium in a reaction that exhibited specificity and concentration dependence. These data suggest that cell-binding sites are available in an active form on the surface of soluble fibronectin. However, the inhibitory effect of fibronectin was greatly enhanced by adding the protein together with heparin, heparan sulfate, collagen, or a fibronectin-binding collagen peptide (CB-7), which is consistent with an "activation" of fibronectin on binding to these matrix components. A similar activation of fibronectin was obtained by cleaving the protein with trypsin. We discuss these findings in relation to conformational rearrangements in the fibronectin molecule. Data is presented supporting a mechanism of cell attachment to fibronectin involving multiple weak interactions between cellular receptors and substrate molecules, although some steps in the attachment process appear to disobey the requirements for such a mechanism.

Animals↗
PubMed2004

Fibronectin matrix turnover occurs through a caveolin-1-dependent process.

Extracellular matrix remodeling occurs during development, tissue repair, and in a number of pathologies, including fibrotic disorders, hypertension, and atherosclerosis. Extracellular matrix remodeling involves the complex interplay between extracellular matrix synthesis, deposition, and degradation. Factors that control these processes are likely to play key roles in regulating physiological and pathological extracellular matrix remodeling. Our data show that fibronectin polymerization into the extracellular matrix regulates the deposition and stability of other extracellular matrix proteins, including collagen I and thrombospondin-1 (Sottile and Hocking, 2002. Mol. Biol. Cell 13, 3546). In the absence of continual fibronectin polymerization, there is a loss of fibronectin matrix fibrils, and increased levels of fibronectin degradation. Fibronectin degradation occurs intracellularly after endocytosis and can be inhibited by chloroquine, an inhibitor of lysosomal degradation, and by caveolae-disrupting agents. Down-regulation of caveolin-1 by RNAi inhibits loss of fibronectin matrix fibrils, fibronectin internalization, and fibronectin degradation; these processes can be restored by reexpression of caveolin-1. These data show that fibronectin matrix turnover occurs through a caveolin-1-dependent process. Caveolin-1 regulation of fibronectin matrix turnover is a novel mechanism regulating extracellular matrix remodeling.

Adenoviridae↗
PubMedDate not supplied

Fibronectin and viral pathogenesis.

Fibronectin is a dimeric high-molecular-weight glycoprotein composed of two similar but not identical subunits. Differences have been observed between plasma and cell-derived fibronectins, and molecular and sequencing studies have revealed a domain structure. The characteristic features of fibronectin include its various molecular and biologic interactions, which can be assigned to the different domains of the molecule. Fibronectin was originally discovered as a protein missing from the surfaces of virus-transformed cells. The importance of functional oncogenes in the loss of extracellular matrices was later established in a number of studies using virus mutants that are temperature-sensitive for transformation. The loss of the extracellular matrix appears to be a result of multiple events in cells but is not a prerequisite for malignant growth in vivo. There appear to be multiple transformed phenotypes, and the loss of extracellular fibronectin may be due in part to proteolytic activity by the cells and other alterations caused by functioning oncogenes. The wide distribution of tissue and soluble forms of fibronectin offers multiple occasions for interactions with other molecules. Binding of fibronectin to viruses and purified viral proteins has been observed in a number of studies. Neuraminidase-sensitive virus-binding sites in the fibronectin molecule have tentatively been identified. Fibronectin also is capable of binding to various complement components, possibly making clearance of viral antigen-antibody-complement complexes, which are observed in the circulation during viral infection, more rapid. The virus-binding ability of fibronectin may play a role in modifying viral infections in the body.

Animals↗
PubMed1994

Expression of fibronectin during rat fetal and postnatal development: an in situ hybridisation and immunohistochemical study.

OBJECTIVE: Fibronectin is a protein of the extracellular matrix with numerous binding sites to the other elements of the matrix and to the cells. The aim of this study was to determine the relative importance of fibronectin isoform expression (FN-EIIIA, FN-EIIIB) during fetal and postnatal development of the rat heart. METHODS: In situ hybridisation and immunolabelling approaches were used to describe the cellular synthesis of fibronectin and its distribution throughout the rat heart from 11 d postconception until adulthood. The distribution of fibronectin was compared to that of laminin and of alpha type III procollagen. RESULTS: The accumulation and pattern of distribution of the major fibronectin mRNA isoforms were identical, that is, there was a progressive decrease in their accumulation as a function of time after 11 d postconception, resulting in a complete absence in the adult. The distribution of fibronectin and procollagen type III mRNAs were, however, quite distinct. At the protein level the time course of synthesis and secretion of the locally synthesised fibronectin (c-FN) did not follow fibronectin mRNA expression, the accumulation of the protein being rather poor, except just before birth, where it was found mainly in the coronary vessels. CONCLUSIONS: During the development of the fetal rat heart fibronectin gene transcription is active and progressively decreases with age, whereas the translation of the mRNAs into their corresponding proteins is always relatively poor. If fibronectin is involved in fetal and postnatal morphogenesis of the rat myocardium, it is the plasma form (p-FN) that is most probably involved in the process of growth and differentiation of the rat heart.

Animals↗
PubMed1982

Comparative influence of blood-borne nonbacterial particles and Staphylococcus aureus on fibronectin, complement and immunoglobulin.

Opsonic fibronectin deficiency has been documented in septic injured patients and suspected to reflect acute depletion due to blood-borne nonbacterial particulates. In the present study, the comparative effect of intravenous infusion of heat-killed Staphylococcus aureus or gelatin-coated nonbacterial test particles on immunoreactive fibronectin, IgG and C3 was investigated. These two test particles were selected because of their known dependence upon adequate opsonization for efficient RES phagocytic removal. The intravenous injection of gelatin-coated RE test lipid emulsion (50 mg/100 gm body weight) resulted in an acute depletion of serum fibronectin with no major alteration in circulating IgG or C3. This selective depletion of fibronectin was followed by a rapid restoration and elevation of fibronectin level within 24 hours. In contrast, intravenous infusion of heat-killed S. aureus (1 X 10 11/rat) resulted in an acute depletion of fibronectin and C2 within 60 minutes. The deficiency of these opsonic proteins after bacterial challenge was followed by elevation of fibronectin and normalization of C2. IgG was not significantly changed at any time. The decline in fibronectin and C3 was greater with an increase in bacterial dose. These studies emphasize the specificity of the opsonic deficiency induced by gelatin-coated particles. Additionally, the suggest that opsonic deficiency with S. aureus bacteremia may be, in part, functionally related to disturbances of fibronectin. The role of fibronectin deficiency in documented states of opsonic deficiency with sepsis warrants consideration.

Animals↗
PubMed1999

Renin-angiotensin system and fibronectin gene expression in Dahl Iwai salt-sensitive and salt-resistant rats.

OBJECTIVE: The tissue renin-angiotensin system and extracellular matrix are involved in the cardiovascular hypertrophy and remodeling induced by hypertension. In this study, we examined the gene expression of the tissue renin-angiotensin system and fibronectin in inbred Dahl Iwai salt-sensitive and salt-resistant rats. MATERIALS AND METHODS: Eight pairs of 6-week-old male Dahl Iwai salt-sensitive and salt-resistant rats were fed either a low- or high-salt diet (0.3% or 8% NaCl, respectively) for 4 weeks. Activities of the circulating renin-angiotensin system were measured by radioimmunoassay and the gene expression of tissue angiotensinogen, the angiotensin II type 1 receptor (AT1) and fibronectin were analyzed by Northern blot analysis. RESULTS: Salt loading significantly increased blood pressure and produced cardiovascular hypertrophy and nephrosclerosis in the salt-sensitive rats. Activities of the circulating renin-angiotensin system were lower in salt-sensitive rats than in salt-resistant rats fed the low-salt diet, and salt loading lowered these activities in salt-resistant rats but not in salt-sensitive rats. In salt-resistant rats, salt loading increased renal, cardiac and aortic angiotensinogen, AT1 and fibronectin messenger (m)RNA expression except for aortic fibronectin mRNA expression. In contrast, in the salt-sensitive rats, salt loading stimulated the expression of cardiac fibronectin and aortic angiotensinogen, AT1 and fibronectin mRNAs. Furthermore, the cardiac and aortic fibronectin mRNA levels in salt-sensitive rats were higher than those in salt-resistant rats when both strains were fed the high-salt diet. CONCLUSIONS: These results demonstrate that the expression of tissue angiotensinogen, AT1 and fibronectin mRNAs is regulated differently in Dahl Iwai salt-sensitive and salt-resistant rats, and indicate that salt-mediated hypertension activates the cardiac fibronectin gene independently of the tissue renin-angiotensin system and stimulates the aortic fibronectin gene with activation of the tissue renin-angiotensin system.

Angiotensin I↗
PubMed1988

Effect of fibronectin-rich human cryoprecipitate on fluid volume requirements in sheep during postoperative sepsis.

Septic surgical patients often require fluid administration to maintain cardiovascular stability due, in part, to the sepsis-induced increase in vascular permeability and associated plasma volume depletion. Plasma fibronectin deficiency exists in such septic patients. We determined if maintenance of fibronectin levels by administration of fibronectin-rich human plasma cryoprecipitate would lower the resuscitative fluid volume needed for support of arterial pressure in septic postoperative sheep which were experimentally depleted of plasma fibronectin. Following a 2-hr postoperative baseline period, denatured collagen (gelatin, 8.7 mg/kg), which has a high affinity for fibronectin, was infused into both control and experimental sheep in order to acutely deplete plasma fibronectin. Sheep were then challenged both intraperitoneally and intravenously with live Pseudomonas (5 x 10(10) bacteria IP; 5 x 10(9) bacteria IV). Experimentals were given fresh plasma cryoprecipitate intravenously at a dose of 4 units bolus, followed by 3 units/hr for 5 hr. Controls received plasma cryoprecipitate selectively depleted of fibronectin by affinity chromatography. Bacterial challenge rapidly resulted in severe systemic hypotension. Ringer's lactate was infused intravenously into both groups at a rate sufficient to maintain a systemic arterial pressure of approximately 50 mm Hg with a maximum pulmonary artery wedge pressure of 15-18 mm Hg. Its rate of infusion was periodically adjusted to maintain this hemodynamic status. Comparison was made of the volume of Ringer's lactate required to maintain an arterial pressure of 50 mm Hg in both groups. Net fluid requirement was significantly (p less than 0.05) less in postoperative septic sheep (47.4 +/- 6.2 mg/kg/hr) treated with fibronectin-rich cryoprecipitate compared to the fluid requirement (71.7 +/- 4.7 mg/kg/hr) for postoperative septic sheep receiving fibronectin-deficient cryoprecipitate. Thus elevation of plasma fibronectin concentration lowers the fluid requirements needed for hemodynamic support in postoperative Gram-negative sepsis.

Animals↗
PubMed1984

Opsonic fibronectin after operation or trauma: effect of hemodilution and duration of operation.

Fibronectin is an essential opsonin for phagocytosis of nonbacterial particulate matter by the reticuloendothelial system (RES). Fibronectin deficiency causes RES phagocytic depression and repletion of fibronectin reverses RES depression. Fibronectin depletion has been linked with multiple organ failure after surgery and trauma in patients with intra-abdominal infection. The mechanisms for fibronectin depletion have not been established. Plasma fibronectin levels were measured in 29 patients requiring operation after trauma and 15 patients undergoing elective abdominal operations. Opsonic fibronectin fell in the immediate postoperative period and on the first postoperative day in both groups. Total fluid replacement, blood loss, and operative time did not correlate with depression in fibronectin levels after trauma, although a weak correlation may exist between total fluid administration and fibronectin concentration in postoperative patients. Total fluid replacement, blood loss, and operative time may be contributing factors, but are not the major determinants of fibronectin deficiency after trauma or operation.

Abdomen↗
PubMed2003

Plasma fibronectin level and its association with coronary artery disease and carotid intima-media thickness.

BACKGROUND: The exact relation of fibronectin with coronary atherosclerosis is unknown. The aim of the present study was to examine the association of fibronectin level with presence and extent of coronary artery disease (CAD) and intima-media thickness (IMT) of common carotid artery (CCA). DESIGN: The IMTs of CCA of 86 patients who underwent coronary angiography were measured; traditional vascular risk factors were also evaluated in these patients. Fibronectin, lipids, C-reactive protein (CRP) and fibrinogen levels were determined. RESULTS: Plasma fibronectin levels of the patients with CAD were found to be significantly elevated compared to patients with normal vessels (0.46+/-0.11 and 0.36+/-0.12 mg/dl respectively, P = 0.001). Fibronectin levels were not associated with extent of CAD. No significant association was observed between fibronectin level and traditional risk factors. IMTs of right and left CCA in patients with CAD were found to be elevated compared to patients with normal vessels (0.89+/-0.1 mm compared with 0.76+/-0.1 mm, P = 0.001 and 0.93+/-0.2 mm compared with 0.71+/-0.1 mm, respectively P < 0.001). Fibronectin levels were positively correlated with CRP (r = 0.45, P < 0.001), low-density lipoprotein-cholesterol (r = 0.23, P = 0.03) and total cholesterol (r = 0.21, P = 0.04) levels and negatively correlated with high-density lipoprotein-cholesterol (HDL-C) levels (r = -0.24, P = 0.02). IMT of left CCA was positively correlated with CRP levels (r = 0.23, P = 0.04) and negatively correlated with HDL-C levels (r = 0.2, P = 0.04). Logistic regression analysis showed that age (P < 0.01) and fibronectin levels (P = 0.01) were independent predictors for the existence of CAD. CONCLUSIONS: The results suggest that fibronectin levels may be a significant predictor of CAD. However, it was shown that fibronectin levels were not associated with extent of CAD and IMT of CCA.

Adult↗
PubMed1984

Human keratinocyte adhesion and phagocytosis promoted by fibronectin.

Epidermal cells from human foreskin or cadaver skin were found to bind and phagocytose fibronectin-coated latex beads but not serum albumin-coated beads. Three lines of evidence suggested that the beads actually were internalized by the cells and not bound only at the cell surfaces. First, the fibronectin coat on internalized beads could be detected with antifibronectin antibodies only if the cells were permeabilized prior to indirect immunofluorescence staining. Second, the internalized beads were not released from the cells by trypsin treatment. Finally, electron microscopic observations showed that the internalized beads were packaged individually and in clusters inside endocytic vesicles in the perinuclear region of the cells. These vesicles had the typical appearance of lysosomes, and, based on the release of trichloroacetic acid-soluble radioactive fragments of fibronectin into the incubation medium, it was concluded that degradation of the fibronectin on the bead surfaces occurred. The epidermal cells that phagocytosed the fibronectin-coated beads were confirmed as keratinocytes according to their electron microscopic appearance and prominent immunofluorescence staining with antikeratin but not anti-plasma fibronectin antibodies. Fibronectin also was found to promote the attachment and spreading of keratinocytes on culture dishes, although the concentration of fibronectin required for half-maximal activity (approximately 5 micrograms/ml) was severalfold higher than the concentration of fibronectin required for spreading of human fibroblasts (approximately 1 microgram/ml). The results suggest the possible importance of fibronectin in mediating adhesion and phagocytosis by keratinocytes, which may be important for the migration of these cells during wound repair.

Antibodies↗
PubMed1981

Distribution of fibronectin during wound healing in vivo.

The distribution of fibronectin during wound healing has been studied. Full thickness wounds were made in the skin on the sides of guinea pigs' trunks. Biopsy specimens were taken from the normal skin, from the 5-hr-old wound, and on days 1-18 after wounding. Unfixed frozen sections were analyzed for fibronectin distribution by indirect immunofluorescence analysis with a specific antiserum prepared in rabbits against guinea pig plasma fibronectin. Tissue samples were also embedded in methacrylate and sections cut and stained with hematoxylin and eosin for general histology or with a silver stain for reticulin. Fibronectin was prominent in the basement membranes of normal skin epidermis. It was also present in the papillary dermis and to a lesser extent in the reticular dermis. After wounding, fibronectin was part of the fibrin clot and distributed along fibrin strands. Fibronectin was also deposited along newly synthesized collagen in the granulation tissue, which was at least in part collagen type III based upon staining for reticulin. Eventually, the entire granulation tissue was transformed into aligned collagen fibrils coated with fibronectin. Throughout the period of wound healing, the level of fibronectin associated with what appeared to be type I collagen in the reticular dermis adjacent to the wound area stayed about the same. When fibrils with the histological characteristics of type I collagen were within the granulation tissue, however, they were coated with fibronectin. The results indicate that fibronectin is a major component present during wound healing.

Animals↗
PubMed1980

Fibronectin and atherosclerosis.

Fibronectin is a polymorphic glycoprotein of plasma, other body fluids and connective tissue, and it occurs in an insoluble and a soluble form. Insoluble fibronectin is found associated with basement membranes and in loose connective tissue matrix as well as in the pericellular matrix formed around cultured adherent cells, such as endothelial, fibroblastic and smooth muscle cells. In these positions fibronectin apparently functions as a substrate for cell attachment and as a scaffold for cell migration and movement. Soluble fibronectin, present e.g. in the circulation (300 micronm/ml) exhibits some important interations with other proteins. It is covalently cross-linked to fibrin during thrombus formation and binds to collagen. Fibronectin is released from platelets during their aggregation and soluble fibronectin potentiates the action of plasminogen activator. We have detected fibronectin in the sub-endothelium, in the matrix of smooth muscle cells of the media and in the adventitia of arteries. By using immunohistological techniques we have further found that fibronectin is prominent in atherosclerotic lesions of the intima, especially in developing fibrous plaques. Fibronectin was also prominent in experimentally induced atherosclerotic lesions. These findings suggest that fibronectin is an indicator of connective tissue formation in atherosclerotic processes and that the protein can have a role in their pathogenesis.

Arteriosclerosis↗
PubMed1998

Different effects of fibronectin on the phagocytosis of Staphylococcus aureus and coagulase-negative staphylococci by murine peritoneal macrophages.

Fibronectin is known to be an important factor in colonization by Staphylococcus aureus of host tissues as well as other extracellular matrix proteins such as collagen and laminin. We investigated the effect of fibronectin on the phagocytosis of the S. aureus Cowan I strain by macrophages and of coagulase-negative staphylococci (CNS) strains for comparison. Fibronectin-reduced serum in place of normal serum lowered the phagocytic activity of the macrophages on the Cowan I strain. Purified fibronectin enhanced the phagocytic activity of the strain in a dose-dependent manner. On the other hand, fibronectin did not show any opsonic effect on the ingestion of CNS strains, though the binding of fibronectin occurred equally well in CNS strains and the Cowan I strain. Fibronectin-binding protein (FnBP), the specific fibronectin receptor on the surface on S. aureus, was detected in both the Cowan I strain and CNS strains. Polymerase chain reaction confirmed that not only the Cowan I strain, but also CNS strains possessed the FnBP gene. These results indicate that fibronectin shows an opsonic effect on the S. aureus, Cowan I strain but not on CNS strains, and suggest that the binding of fibronectin to FnBP is not sufficient for efficient phagocytosis of the staphylococci strains by macrophages.

Adhesins, Bacterial↗
PubMed1985

Fibronectin binds to complement-coated agarose beads and increases their association to mouse macrophages.

We have studied the binding of fibronectin to complement (C3b, C3bi, C3d)-coated agarose beads and its effect on cell association of such beads to mouse macrophages. Fibronectin bound to agarose beads preincubated in human serum, whereas no binding occurred after preincubation of the beads with complement-inactivated (50 degrees C for 20 min or ethylenediaminetetraacetic acid) sera. The binding of iodine-labelled fibronectin to beads preincubated in fibronectin-depleted serum (HS-FIB) was about twice that of beads preincubated in normal serum. Unlabelled fibronectin inhibited the following binding of labelled fibronectin to beads pretreated in HS-FIB. A similar amount of fibronectin bound to agarose beads coated with equimolar amounts of C3b, C3bi, or C3d, suggesting that the common domain C3d carries the main binding site(s) for fibronectin. Preincubation of serum-treated and trypsinized agarose beads with fibronectin led to an increased association (22%) of such beads to mouse macrophages. The results indicate that fibronectin promotes binding of complement-coated agarose beads to mouse macrophages, whereas the ingestion of the beads is mediated via complement C3 receptors.

Animals↗
PubMed1986

Fibronectin binding to C1q associated with antigen-antibody complexes in EDTA-treated plasma.

In this report we have investigated the association of fibronectin with antigen-antibody-C1q complexes incubated in fibronectin-depleted and C1q-depleted plasma. When BSA--anti-BSA immune aggregates are incubated in plasma depleted of both fibronectin and C1q to which 125I-fibronectin has been reconstituted, little radio-activity is bound to the immune complexes. However, pre-incubation of immune complexes with purified C1q prior to incubation in the plasma causes an approximately 10-fold increase in the amount of radioactivity bound. The binding of 125I-fibronectin to preformed antigen-antibody-C1q complexes is specific, since the reaction is inhibited by the addition of unlabelled fibronectin but not by ovalbumin. When antigen-antibody-C1q complexes are incubated in C1q-depleted plasma containing physiological concentrations of fibronectin, and analysed by immunoblotting, fibronectin antigens are detected on the immune complexes. Identical results are obtained using immune complexes composed of sheep erythrocyte rabbit anti-sheep erythrocyte C1q (EAC1q) cells. There is no specific requirement for preformed antigen-antibody-C1q complexes, since fibronectin can be detected on antigen-antibody complexes after incubation in normal human serum or in C1q-depleted ethylenediamineteraacetic acid (EDTA) serum reconstituted with purified C1q prior to incubation with the complexes. Finally, we also demonstrate that in the presence of C1q, 125I-fibronectin will associate with soluble antigen-antibody complexes.

Animals↗
PubMed1986

Serum and plasma fibronectin binds to complement reacted immune complexes primarily via Clq.

The binding of fibronectin to human Clq, C3b, and complement-reacted immune complexes (IC) was investigated by enzyme-linked immunosorbent assays. Microplates were coated with BSA followed by incubation with rabbit-anti-BSA IgG or F(ab')2 fragments of rabbit anti-BSA. Incubation of the solid phase with serum at 37 degrees C caused attachment of Clq and C3b. Addition of EDTA to the serum inhibited the binding of C3b, but not Clq, whereas substitution of the anti-BSA IgG on the solid phase with the F(ab')2 fragments abrogated the Clq, but not the C3b binding. Fibronectin binding was observed after incubation of the solid-phase IC with serum or plasma at conditions where Clq was also bound, whereas only minor amounts of fibronectin bound to the solid phase IC via C3b. Purified fibronectin showed a dose-dependent binding to solid-phase IC pretreated with Clq or fibronectin-depleted serum, confirming that the binding of fibronectin to IC largely occurred via Clq. Significantly smaller amounts of fibronectin were bound to solid-phase IC incubated with plasma instead of serum, despite the higher fibronectin concentration in plasma. This difference was found not to be due to a fibrinogen-fibronectin interaction in plasma. Binding of fibronectin to preformed fluid phase IC incubated with serum was demonstrated by SDS-PAGE analysis of PEG-precipitated IC.

Antigen-Antibody Complex↗
PubMed1996

Lipopolysaccharide increases cell surface-associated fibronectin in fibroblasts in vitro.

This study assessed the fibronectin expression by fibroblasts derived from noninflamed and inflamed gingiva by measuring the amount of cell surface-associated fibronectin and fibronectin released into the medium. The effects of added lipopolysaccharide from Porphyromonas gingivalis, Prevotella nigrescens and Escherichia coli on both types of fibroblasts were also studied. In the absence of lipopolysaccharide, the amounts of the two types of fibronectin were significantly larger in the fibroblasts from inflamed than from noninflamed gingiva. The specific lipopolysaccharide had no effect on the amount of fibronectin released into the medium by either fibroblast type. The amount of cell surface-associated fibronectin increased significantly when lipopolysaccharide (0.1 and 1 microgram/ml) was added to the cells from the noninflamed gingiva (the effect was evident in the order: P. gingivalis>P.nigrescens>E. coli). Lipopolysaccharide from P. gingivalis significantly increased the cell surface-associated fibronectin even at a low concentration of lipopolysaccharide (0.01 microgram/ml). In fibroblasts from the inflamed gingiva, only the lipopolysaccharide from P. gingivalis was effective in increasing the amount of cell surface-associated fibronectin. Our findings showed that the fibronectin expression was increased in the fibroblasts from inflamed gingiva and that lipopolysaccharide from P. gingivalis increased the cell surface-associated fibronectin.

Analysis of Variance↗