Ultrastructural aspects of interactions of platelets with microcrystalline collagen.

Whole blood anticoagulated with EDTA was stirred with high concentrations of a microcrystalline bovine dermal collagen preparation in order to study the interactions of blood cells with collagen at the ultrastructural level. Blood from normal subjects and from patients congenitally deficient in Factors VIII or XII or with thrombasthenia or von Willebrands disease was used. In scanning and transmission electron microscopic studies with blood from normal subjects and patients, platelets were seen to adhere to collagen, develop cell surface undulations, form pseudopods, and undergo morphologic changes suggestive of the release reaction. Although thrombasthenic platelets adhered to collagen, pseudopods formed by these cells were remarkably angulated and nodular. Relatively few von Willebrands platelets adhered to collagen, but those platelets that did adhere underwent the usual sequence of morphologic changes.