A radioimmunoassay technique for the fragment Eneo-antigens in plasma was developed. Specific antibody to the Eneo-antigen was obtained from anti-E rabbit serum through a fibrinogen-Sepharose column. There was no interference on binding between Eneo-antibody and 1251-E even though hundreds mg of fibrinogen were present in a sample to be tested. Therefore, the method was applicable to plasma sample, permitting quantitation of the E-related neoantigens more than 1 ng/ml. On the Eneo-antigenicity,

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... electro-blotting study showed that the products of fragments X and Y which were generated in the early stage of fibrinolysis were bearing the antigenicity. Among the chains of fibrin and fibrinogen molecules, 9 and r chains were strongly suggested to be the loci of Eneo-antigenic sites.