Stewart A. Cederholm-Williams

Neutralizing antibodies to streptokinase four years after intravenous thrombolytic therapy

Neutralization antibodies to streptokinase increase to high levels within several days of administration. It is not known how long these high levels persist. The time course of antibody levels needs to be further characterized owing to the increasing need to readminister thrombolytic therapy, and to the possibility that these antibodies may compromise the safety and efficacy of a further dose of streptokinase or streptokinase-containing compounds. In this study, paired streptokinase neutralization titers (in vitro functional assay) and specific antistreptokinase immunoglobulin G (IgG) antibody levels were measured in 145 patients who received streptokinase between 10 and 48 months previously. Serologic evidence of recent streptococcal infection was also sought. Neutralization titers sufficient to inactivate a conventional dose of 1,500,000 units of streptokinase were still present in 50% of patients (95% confidence interval 36-64) at 24 months, 48% (34-62) at 36 months, and 51% (37-71) at 48 months after streptokinase administration. Levels of specific antistreptokinase IgG antibodies also remained constant over the 1- to 4-year period. Neutralization titers were weakly correlated with specific IgG levels (r = 0.35). Antistreptolysin titers > or = 250 and > or = 333 IU/ml were present in 30% (24-38) and 12% (8-18) of these patients, respectively. Neutralization titers were not correlated with antistreptolysin titers. Neutralizing antibodies (assessed by an in vitro functional assay) remained high in 51% of patients 4 years after intravenous streptokinase administration. It is not known whether persisting high in vitro neutralization titers affect the efficacy and safety of repeat administration of streptokinase or streptokinase-containing compounds.

The compact domain conformation of human Glu-plasminogen in solution

A complete understanding of the accelerating mechanisms of plasminogen activation and fibrinolysis necessarily requires structural information on the conformational forms of plasminogen. Given the absence of high-resolution structural data on plasminogen the use of lower resolution approaches has been adopted. Two such approaches have previously indicated a compact conformation of Glu-plasminogen (Tranqui, L., Prandini, M., and Chapel, A. (1979) Biol. Cellulaire, 34, 39-42; Bányai, L. and Patthy, L. (1985) Biochim. Biophys. Acta, 832, 224-227) whereas a third has suggested a fairly extended conformation (Mangel, W., Lin, B. and Ramakrishnan, V. (1990) Science, 248, 69-73). Native Glu-plasminogen has been investigated using small-angle X-ray scattering (SAXS) experiments. It is concluded that this molecule in solution is compact (radius of gyration, RG 3.05 +/- 0.02 nm and maximum intramolecular distance, Im 9.1 +/- 0.3 nm) and that the data are consistent with the right-handed spiral structure observed using electron microscopy by Tranqui et al. (1979). A spiral structure of native plasminogen would have important implications for the conformational response of plasminogen to fibrin and concomitant stimulation of plasminogen activation.

Cardiolipin antibody levels in endometriosis and systemic lupus erythematosus

Cardiolipin antibody levels were found to be significantly higher in women with endometriosis and SLE when compared with healthy women.

Urokinase—the enzyme responsible for invasion and metastasis in human breast carcinoma?

Raised levels of tissue fibrinolytic activity have been observed in certain malignant tissues and these may determine metastatic spread. We have investigated the fibrinolytic enzymes tissue plasminogen activator (tPA) and urokinase (UK) in 26 breast carcinomas and 13 benign breast biopsies. The extracts were analysed for overall fibrinolytic activity on fibrin plates and by fibrin-overlay zymography after electrophoresis on SDS-PAG. Supernatants of the extracts were analysed by an antigenic immunoassay (ELISA) and a functional bioimmunoassay (BIA) using polyclonal antibodies and chromogenic substrates. All tissues contained similar tPA levels. Malignant extracts contained significantly increased UK compared with benign extracts (1.60 ± 0.37 iu/ml, 0.36 ± 0.16 iu/ml; P < 0.002). Zymography showed no inhibitor complexes and UK was almost exclusively confined to malignant tissues (x2 = 5.04, P < 0.025). The results suggest malignant transformation of breast is associated with the uninhibited and significantly increased production of UK, which may be responsible for the characteristics of malignant growth.

Effect of bradykinin on the exposure of tissue plasminogen activator from human endothelial cells

Human umbilical vein endothelial cells cultured on plastic microcarrier spheres were used in an acute release model to study tissue plasminogen activator (t-PA) and von Willebrand factor (vWF). No consistent acute release of t-PA could be directly demonstrated but several agents induced vWF release including preformed plasmin and plasminogen in the presence of t-PA. Bradykinin induced a small release of vWF when perfused singly over endothelial cells but much more in the presence of plasminogen. It is postulated that this is an indirect demonstration of active t-PA exposure at the endothelial surface due to bradykinin.

Detection of Antibodies to Vascular Endothelium: A Possible Contribution to Thrombosis

Abstract Vascular endothelium is very important in the control of fibrin deposition, and defects of function often lead to thrombosis. Microvascular disease and thrombosis are clinical features of systemic lupus erythematosus (SLE), and anti-phospholipid antibodies have been implicated in the pathogenesis of thrombosis in this disease. In order to detect autoantibodies directed against endothelium, cells were harvested from human umbilical veins and grown to confluence in microtitre plates. The monolayers were fixed, incubated with dilute SLE or control sera, and specifically bound IgG quantitatively detected using alkaline-phosphatase conjugated goat anti-human IgG antibody. No significant binding was shown by 28 healthy control sera (median 0%, range 0–8%), whereas the 73 SLE sera tested exhibited significant binding (median 15%, range 0–115 % P