The Platelet-fibrin Relationship in Human Blood Clots: an Ultrastructural Study Utilizing Ferritin-conjugated Anti-human Fibrinogen Antibody.

T HE RELATIONSHIP of platelets and fibrin has interested investigators since the early descriptions of human blood clots.’4 Many studies showed an intimate platelet-fibrin association which indicated that platelets served as centers of clot formation, and as the main support of the fibrin meshwork.5’#{176} Other reports, however, described the relationship to be accidental; that is, platelets and the network of developing fibrin strands were related in the clot by mutual adhesiveness, rather than by specific structural connections.79 We have used electron microscopic technics to study platelet clots formed in vitro from recalcified platelet rich plasma.1#{176} The ultrastructural observations have indicated a specific association of fibrin strands and altered alpha granules of platelets in the clot. In order to further identify the platelet-fibrin relationship we have combined suitable immune technics11 with our electron microscopic observations. Ferritin-conjugated antihuman fibrinogen antibody was incubated with platelet-rich human plasma during clot formation. Examination of the clots revealed the ferritin labeled antibody in developing fibrin, and in platelets undergoing viscous metamorphosis. These observations support the fact that fibrin strands outside the platelet are related to the granulomere within the altered cell.