Gel-filtered pooled plasma from healthy blood donors.

Immunoblots are shown from an in vitro experiment on the effect of ancrod and thrombin on proteolytic release of the factor XIII activation peptide and the catalytic activity of factor XIII leading to the formation of fibrin γ-chain dimers and trimers. Pooled plasma from healthy blood donors was incubated without enzyme, with ancrod, or with thrombin in absence or presence of recombinant hirudin and calcium chloride, as specified in the graph. Panel A shows an immunoblot using a polyclonal antiserum against the activation peptide of factor XIII. A polyclonal antiserum against the γ-chain of fibrinogen was used for the immunoblot in panel B. Addition of thrombin (lane 11) or intrinsic formation of thrombin after addition of calcium in the absence of hirudin (lane 3) led to disappearance of the factor XIII band and appearance of cross-linked γ-chains. Parallel addition of ancrod and calcium chloride led to the formation of γ-chain cross-links, also in presence of hirudin, even though there is no decrease in the factor XIII band. This indicates that the factor XIII zymogen is able to cross-link desAA-fibrin γ-chains formed by the action of ancrod in the presence of calcium.