Surface Factor Mechanisms in Relation to Blood Platelets: Evidence that Activated Hageman Factor is Present on the Surface of Platelets*

Abstract

SummaryBlood platelet suspensions from normal (N) or hemophilia A (VIII-) subjects contain active SF (surface factor or activation product) in their plasmatic atmosphere. Since factor XII is an essential precursor, SF is not formed on platelets from a Hageman-deficient. Experimental evidence establishing these facts was obtained by means of clotting tests (PCa and PTT) and the thrombelastograph (TEG). The SF activity of normal platelets, like a plasma SF preparation, corrects the deficiencies in XII- plasmas, best tested in silicone or the stainless steel cuvette of the TEG. An anti-SF preparation inhibited the platelet SF activity. Allowing for the SF effect, there was no evidence for any significant factor VIII (AHF) in the platelet plasmatic atmospheres.How surface factor (SF) activation from precursors (XII, XI) in the plasma and plasmatic atmosphere of altering platelets may combine in a mutually reinforcing reaction to trigger intrinsic blood clotting is discussed. When stress, vascular injury, stasis, and other factors enter the picture, the stage may be set for the occurrence of thrombosis in vivo.