Summary
Immunoglobulin 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.
Keywords
Antiphospholipid syndrome - immunoglobulin G - fibrin - plasmin - fibrinolysis
