Occlusion of Plasma Proteins by Human Fibrin: Studies using Trace-Labelled Proteins

S ummary The occlusion of 13 different proteins by human fibrin has been investigated using radioactive techniques. Each of the proteins examined exhibited different tendencies to be retained by clots. For a satisfactory demonstration of this, studies of the effects of varying protein and fibrinogen concentration were required and are reported here.
With normal plasma, the contamination of the syneresed and washed fibrins with albumin and transferrin was negligible whereas significant quantities of β-lipoproteins, haptoglobin-haemoglobin complex, free haemoglobin and IgG-globulins were trapped. Substantial contaminations were noted with macroglobulins (IgA, IgM and α₂-macroglobulin), and above all with plasminogen, of which more than 50 per cent was adsorbed to the fibrin. Bence Jones proteins were also occluded by fibrin, Type K more so than Type L, whereas iodinated thrombin showed no affinity for fibrin.
Some effects of clotting conditions on occlusion are also reported, and it is shown that in dilute plasmas occlusion is reduced and in covalently bound fibrin it is enhanced.