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Biomedical subjects

K D Forsyth

Publications and source records attributed to K D Forsyth.

17 recordsLinked to original sources
PubMed1994

Endothelial serpins--protectors of the vasculature?

Vascular damage, initiated by host inflammatory cells, is a component of the pathophysiology of many acute and chronic inflammatory disorders. Neutrophil-mediated tissue damage is mediated primarily by proteinases, particularly elastase and cathepsin G. In this study we have identified endothelial binding of two key serine proteinase inhibitors (serpins), alpha 1-antitrypsin, the inhibitor of elastase, and alpha 1-antichymotrypsin, the inhibitor of cathepsin G. These serpins are shed from the endothelium into the supernatant when neutrophils adherent to the endothelium are activated. Endothelium activated by lipopolysaccharide (LPS) augments this process. Serpin-proteinase complexes activate neutrophils and induce further cytokine release, thereby amplifying inflammatory processes. Strategies aimed at preventing endothelial serpin depletion may help minimize vascular damage during inflammation.

Adult↗
PubMed1994

Plasma fibronectin levels in extremely preterm infants in the first 8 weeks of life.

Fibronectin has in the past been considered to function simply as a non-specific plasma opsonin. However, recent studies have demonstrated that this molecule plays an important role in fundamental components of the immune response, for example, neutrophil adhesion, T cell activation and endothelial function. Additionally, fibronectin is important in lung homeostasis where it contributes to alveolar epithelial integrity. In this study plasma fibronectin levels were measured longitudinally in a group of extremely preterm infants, mean gestational age 27 weeks. Plasma fibronectin levels at birth were significantly lower in the preterm study group than in term controls (mean 91 +/- 33 micrograms/mL compared with 214 +/- 62 micrograms/mL in the term controls, P < 0.0001). The preterm cohort demonstrated a more than two-fold rise in plasma fibronectin on days one and two; levels fell almost to baseline values by day three with a subsequent slow rise to a plateau by day 28. No further increase was seen by day 56. This sequence of early changes in fibronectin levels mirrored closely the time course of respiratory distress syndrome. Infants of mothers with pre-eclampsia had significantly lower peak fibronectin levels than in those without (P = 0.016), and those infants with bronchopulmonary dysplasia showed a trend towards lower basal fibronectin levels (P = 0.07) and a greater difference between peak and basal levels (P = 0.05). Neonates, particularly those born preterm, have blunted immunological responses to infection. Fibronectin plays a key role in immunological responsiveness. The significant changes in fibronectin levels after birth in the preterm neonate are likely to have important pathophysiological consequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Expression of the leukocyte common antigen CD45 by endothelium.

The CD45 family of Ag expressed by leukocytes play a key role in lymphocyte activation. In this study, we identify both a restricted pattern of expression of CD45 Ag by human endothelial cells and differences in m.w. of endothelial CD45 compared with lymphocyte CD45. Initially, immunoperoxidase staining of endothelial cells in culture revealed the presence of the CD45RO isoform provided the endothelial cells had been stimulated by IL-1 for several days. No other isoform of CD45 was detected by immunoperoxidase staining of endothelium. Leukocyte common antibodies, reputed to detect all isoforms of CD45, did not detect endothelial CD45RO. A polymerase chain reaction method was then used to demonstrate that the message for the CD45RO isoform was constitutively present, with increased levels after IL-1 stimulation. Western blot confirmed the presence of the RO isoform. No other CD45 isoform was detected, either by PCR amplification for message or by Western blot. There were clear differences between lymphocyte and endothelial CD45. The RO isoform expressed by endothelium has an estimated M(r) of 235,000 in contrast to lymphocyte RO that, on our gels, has an estimated M(r) of 190,000. Given the large surface area of endothelium (approximately 1 km2 in the human), the close apposition of lymphocytes and endothelium in immunologic tissues such as lymph nodes, and the pivotal role CD45 plays in activation, expression of CD45RO by endothelium may have important implications in lymphocyte-endothelial interactions. This is most likely to occur in endothelium after a few days of IL-1 stimulation, e.g., at sites of chronic inflammation, or in the draining lymph node of an inflammatory focus.

Actins↗
PubMed1993

Wiskott Aldrich syndrome: an immunodeficiency syndrome not rare in Western Australia.

Wiskott Aldrich syndrome, a combined cellular and humoral X-linked immunodeficiency, is generally considered to be rare. The aim of this study was to ascertain the true prevalence in the paediatric population in Western Australia, describe the clinical features, and summarise the current literature on this unusual condition. All cases of Wiskott Aldrich syndrome presenting to Princess Margaret Hospital in Perth during the period from January 1960 to January 1990 were identified by a retrospective review of case records and by interviewing hospital immunology, haematology and general clinical staff. Nine cases of Wiskott Aldrich syndrome are described, demonstrating that the prevalence of Wiskott Aldrich syndrome in Western Australia is nine times that expected from previous reports. Death occurred in a number of patients before the correct diagnosis was recognised. The clinical features in this group are quite variable. Low isohaemagglutinins, elevated IgE, blunted DTH skin multitest, and very low CD8 numbers are however consistent features. Wiskott Aldrich syndrome may be more prevalent than previously recognised, and should be considered in males with thrombocytopenia and infection.

Adolescent↗
PubMed1993

Decreased plasma fibronectin concentrations in preterm infants with septicaemia.

Changes in plasma fibronectin concentrations were determined during bacterial septicaemia in extremely preterm infants. The study was a prospective study of fibronectin concentrations in infants of less than 30 weeks' gestation. Concentrations were determined at birth, before sepsis, and throughout the episode of sepsis. Fibronectin concentrations at birth or immediately before sepsis were not significantly different between those infants who developed septicaemia and those who did not (98 (15) v 97 (10) micrograms/ml). In the infants with septicaemia, fibronectin concentrations decreased significantly on day 1 (106 (13) v 173 (18) micrograms/ml for the controls) and remained significantly lower on day 2 (123 (26) v 201 (17) micrograms/ml). By day 5 fibronectin concentrations had increased and were no longer statistically different from controls. Fibronectin is a key modulator of the immune response, with important functions in neutrophil adhesion, bacterial opsonisation, T cell activation, and vascular integrity. Acute depletion of plasma fibronectin during sepsis in preterm neonates may further abrogate their ability to control sepsis.

Bacteremia↗
PubMed1991

Assessment of endothelial immunophenotype--limitation of flow cytometric analysis.

Flow cytometry is generally utilized to quantify antigen expression by cells in suspension. To detect antigens on endothelium, which grows as a monolayer, either the creation of a suspension of endothelial cells for flow cytometry, or the use of alternative techniques (such as immunoperoxidase staining) is required. We demonstrate here that creating suspensions of endothelial cells for flow cytometry underestimates the expression of certain antigens. In addition, morphological information regarding certain antigens (serpins and fibronectin) is only discernible by immune microscopy, a subjective procedure. We would recommend caution in using flow cytometry for the estimation of endothelial antigens. Using computerized estimates of microscopic immunostaining (e.g., with video image analysis) it may be possible to overcome some of the subjective limitations of immune microscopy.

Antigens↗
PubMed1991

Anti-CD9 antibodies augment neutrophil adherence to endothelium.

Anti-CD9 antibodies which bind to the CD9 (p24) antigen are known to induce platelet and pre-B-cell aggregation. We show here that human endothelium expresses the CD9 antigen, and anti-CD9 antibodies incubated with endothelium induce a rapid increase in adhesion of neutrophils to endothelium by an action on the endothelial cell. This augmented adhesion is not mediated by glycoprotein IIb/IIIa or by the leucocyte integrins. Binding of anti-CD9 antibody to CD9 induces shedding of the CD9/anti-CD9 complex off the endothelial cell in a time-dependent manner. It is likely that CD9 binding to its ligand induces an activation event within the endothelial cell, resulting in surface expression of a pre-formed adhesive ligand for the neutrophil, or an activation change to a constitutively expressed ligand to render it functional.

Antibodies↗
PubMed1990

Preparative procedures of cooling and re-warming increase leukocyte integrin expression and function on neutrophils.

The majority of studies involving neutrophil integrin expression and function are performed at physiological temperatures subsequent to routine preparative procedures at 4 degrees C. We have shown that surface expression of the leukocyte integrin molecules on neutrophils is increased by cooling and subsequently re-warming of neutrophils to 37 degrees C when compared with cells held at room temperature or 37 degrees C. This increase in expression is secondary to prior cooling of the neutrophils. There is an associated increase in function of these newly expressed adhesion molecules, making the neutrophils more adherent to endothelium. Preparation of cells at 4 degrees C and subsequently warmed to 37 degrees C is stimulatory for neutrophils, probably causing translocation of intracellular stores of the leukocyte integrins to the cell surface in a manner analogous to the stimulant FMLP. Our results indicate that the cooling of neutrophils during isolation is an inappropriate method of neutrophil preparation.

Adult↗
PubMed1990

Fibronectin degradation; an in-vitro model of neutrophil mediated endothelial cell damage.

We have observed that fibronectin has a characteristic fibrillar morphology within the extracellular matrix surrounding endothelial cells. This morphology, which is easily recognizable by conventional immunoperoxidase techniques, is disrupted if neutrophils are induced to degranulate on endothelial monolayers. Loss of the fibrillar morphology (degraded fibronectin) is characterized by fragmentation and diffuse spreading of fibronectin over the surface of the endothelial cells. Loss of the normal fibronectin architecture following neutrophil degranulation is more rapid and extensive in endothelium pretreated with Interleukin-1 (IL-1). In addition, there is loss from the fibronectin molecule of a chymotryptic protease-sensitive epitope recognized by a cellular fibronectin specific antibody. Degraded fibronectin is stimulatory for neutrophils, and is likely to induce further fibronectin breakdown. This sequence has the potential to set up an amplification inflammatory loop with neutrophil mediated loss of vascular homeostasis. Alteration of fibronectin architecture is a useful marker of endothelial injury, and has important pathophysiological consequences.

Cell Degranulation↗
PubMed1989

Neutrophil-mediated endothelial injury in haemolytic uraemic syndrome.

Neutrophil leucocytosis is associated with a poor outcome in the haemolytic uraemic syndrome (HUS). This study tested the hypothesis that neutrophils from HUS patients are activated and through release of their intracellular contents damage endothelium. The proportion of neutrophils adhering to endothelium in culture was twice as high for HUS patients' neutrophils as for control neutrophils (n = 12). In addition, these neutrophils induced endothelial injury, assessed morphologically by degradation of endothelial cell fibronectin. In an attempt to inhibit neutrophil adhesion and subsequent endothelial damage the hyperadhesive neutrophils from HUS patients were incubated with a CD18 antibody directed against the common beta chain of the leucocyte integrin molecules. The CD18 antibody was able to abrogate endothelial damage in four of the ten subjects studied. These observations suggest that the neutrophil is of prime pathophysiological importance in HUS, and that methods aimed at reducing neutrophil adhesion and neutrophil-mediated endothelial damage are likely to be beneficial.

Acute Disease↗
PubMed1989

Lung immunoglobulins in the sudden infant death syndrome.

The incidence of the sudden infant death syndrome parallels that of respiratory tract infections in the paediatric community. On the basis that the aetiology of the sudden infant death syndrome may lie in an unusual response to a trivial intercurrent respiratory infection a necropsy study was carried out investigating pulmonary immunoglobulins in 16 victims of the syndrome and a series of infants (controls) who had died of non-pulmonary causes. Compared with the controls victims of the sudden infant death syndrome had grossly raised concentrations of IgG, IgM, and to a less extent IgA in lung lavage samples. In addition, pulmonary interstitial and terminal airway cells expressing these immunoglobulins were identified far more often in victims than controls. The study failed to determine whether the increased immunoglobulin concentrations were a consequence of an unusual response to a trivial infection or an expression of otherwise altered immunological control in the respiratory tract. Epidemiological evidence and the findings of this study suggest that the respiratory tract is the prime target organ in the sudden infant death syndrome.

Bronchoalveolar Lavage Fluid↗
PubMed1989

CD15 antibodies increase neutrophil adhesion to endothelium by an LFA-1-dependent mechanism.

Anti-neutrophil antibodies (CD15) bind to a simple sugar (lactose-N-fucopentaose III, LNF III) known to be present on the chains of the adhesion molecules on neutrophils. We have demonstrated that pre-incubation of neutrophils with a CD15 antibody increases neutrophil adherence to endothelium by a neutrophil-dependent mechanism. This augmented adhesion can be inhibited by antibodies directed against the alpha and beta chain of the leukocyte function-associated antigen 1 (LFA-1) molecule. There is also some increase in surface LFA-1 expression on neutrophils after CD15 incubation, suggesting that CD15 antibodies increase neutrophil adhesion by an LFA-1-dependent mechanism. The increase in LFA-1 expression after CD15 incubation occurs in the presence of a protein synthesis inhibitor. As LFA-1 is not stored intracellularly, the increased adherence of the neutrophils, and increased LFA-1 expression on their surface, suggests the possibility that the CD15 antibodies are binding to the LNF III antigen present on the alpha and beta chains of LFA-1, producing their effect by activating the molecule, perhaps by exposing new antigen sites by a stearic effect.

Antigen-Antibody Reactions↗
PubMed1989

Role of the LFA-1 adhesion glycoprotein in neutrophil adhesion to endothelium and plastic surfaces.

Neutrophil adherence to endothelium is known to be mediated, at least in part, by adhesion molecules such as LFA-1. Deficiency of these adhesion molecules leads to recurrent infection and early death from infection. As screening for defects of these adhesion glycoproteins is often performed by the ability of neutrophils to adhere to plastic plates, in this study a comparison of neutrophil adherence by the CD18/CD11a (LFA-1) mechanism to endothelium and plastic surfaces was examined. Baseline neutrophil adherence was two-fold higher to plastic than to endothelium (17% +/- 9 for plastic, 8% +/- 5 for endothelium). Baseline adherence to endothelium was partially inhibitable by anti-LFA-1 antibodies, whereas no inhibition of adherence occurred on plastic. Neutrophil stimulants increased adherence to both surfaces, although only on endothelium was this increase attributable to the LFA-1 mechanism. IL-1 increased adherence to endothelium, but had no effect on plastic. We conclude that adherence of neutrophils to plastic surfaces probably represents overall activation status through undefined mechanisms, is not by LFA-1 receptor ligand interactions, and is therefore a non-physiological phenomenon. Endothelial receptors are pivotal in neutrophil adherence. It would be more appropriate to screen leucocytes for leucocyte adhesion deficiency by assaying for specific receptor occupancy with monoclonal antibodies, rather than an assay such as adhesion to plastic where the adhesion ligand is non specific.

Antigens, Differentiation↗
PubMed1988

IgG antibodies to Aspergillus fumigatus in cystic fibrosis: a laboratory correlate of disease activity.

Serum was collected from 50 patients with cystic fibrosis, and IgG antibodies to Aspergillus fumigatus were measured by enzyme linked immunosorbent assay (ELISA). In addition, total IgE and Aspergillus specific IgE antibodies were measured in 41 of the 50. A close association was found between pulmonary function and clinical state, and IgG antibodies to Aspergillus. There was no association between pulmonary function or clinical state and IgE antibodies. It is postulated that in patients with cystic fibrosis, Aspergillus fumigatus may contribute to deterioration in pulmonary function by local pathogenicity, or by hypersensitivity mechanisms mediated by IgG.

Adolescent↗
PubMed1988

Immunocytologic characterization using monoclonal antibodies of lung lavage cell phenotype in infants who have died from sudden infant death syndrome.

The phenotype of cells obtained from pulmonary lavage in infants who have died from sudden infant death syndrome were examined and compared with cells from control subjects. The only striking difference between the groups was a lack of reactivity of lavage cells with antibody of the CD14A cluster in the sudden infant death syndrome subjects, while antibodies of the CD14B cluster reacted strongly with cells from both the sudden infant death syndrome group and controls. Major histocompatibility complex class II antigens were expressed on approximately 95% of lavage cells, with DQ expressed more frequently than DR or DP. The majority of the lavage cells was macrophages, yet they reacted with CD3 (OKT3) and CD8 (OKT8) antibodies. No interleukin 2 was found in the lavage fluid.

Antibodies, Monoclonal↗