Immunoglobulin G from Patients with Antiphospholipid Syndrome Impairs the Fibrin Dissolution with Plasmin

Abstract

SummaryImmunoglobulin G (IgG) isolated from normal human blood plasma stabilizes the structure of perfused crosslinked fibrin and prolongs the time for its dissolution with plasmin, when the fibrin surface is exposed to 500 s-1 shear rate flow. The IgG from patients suffering in antiphospholipid syndrome with thrombotic complications exerts even stronger antifibrinolytic effect. A patient, whose IgG does not affect the fibrin dissolution with plasmin, displays a bleeding tendency. The shear stress-induced disassembly of the fibrin clots containing IgGs with antifibrinolytic potency occurs at a much more advanced stage of fibrin digestion, as evidenced by the electrophoretic pattern of the ureatreated samples. The antifibrinolytic effects are also produced under static conditions and these are caused by the variable portion of the IgG molecules (fragment Fab), whereas the constant part (fragment Fc) has no inhibitory effect. The IgGs with antifibrinolytic properties do not affect directly the plasmin activity in amidolytic assay, but the IgGs from APS patients obliterate the competition of the fibrin and the peptidyl-p-nitroanilide for the protease in the same assay system suggesting interference of the IgGs with the plasmin action on the fibrin substrate. Thus, the correlation of the clinical symptoms with the effect of the isolated IgG on the dissolution of perfused fibrin clots supports a physiological and a pathological role of IgG in the fibrinolytic process related to the variability of the cross-reactions of immunoglobulins with fibrin, fibrin degradation products or fibrin-plasmin complexes.

Identification of Anti-Plasmin Antibodies in the Antiphospholipid Syndrome That Inhibit Degradation of Fibrin

“…In 2000, Cugno et al (36) showed that of 39 patients with primary APS, three had high titers of IgG Ab against t-PA, and four had high titers of Ab against fibrin-bound t-PA, which is the physiologically active form of t-PA. Very recently, Kolev et al (37) reported that IgG from APS patients impaired the fibrin dissolution with plasmin. Interestingly, these investigators noticed that although normal human IgG appeared to slightly retard the FIGURE 7.…”

Decreased fibrinolytic potential and morphological changes of fibrin structure in dermatitis herpetiformis

“…This assay was described earlier [15]. Briefly: freshly, simultaneously prepared plasma and serum samples were analysed within 1 h after collection without freezing to avoid cryoprecipitation.…”

Antiphospholipid Antibodies and APS Nephropathy

“…Isolated aPL antibodies with activity against plasmin as well as whole IgG from APS patients, have been found to impair plasmin-mediated fibrinolysis [41,42]. A subsequent study of the reactivity of aPL with tissue plasminogen activator (tPA), another fibrinolytic factor sharing homology with plasmin, showed that several of these aPL were able to reduce tPA activity in converting plasminogen to plasmin [43,44].…”