Summary
Blood 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.