Platelet-collagen interactions: increase in rate of adhesion of fixed
washed platelets by factor VIII-related antigen
M Aihara, HA Cooper and RH Wagner
A simple technique using an aggregometer and fixed washed human platelets
(FWP) and fibrillar collagen has been used to evaluate the contribution of
the two components of the factor VIII (FVIII) complex to platelet-collagen
interactions. FWP bound individually to collagen fibrils in suspension, and
both the total number of FWP bound and the rate of adhesion increased with
increasing collagen concentration. Von Willebrand's disease (vWD) type I or
normal plasma immunoadsorbed with anti-factor VIII-related antigen
(anti-FVIIIR:Ag) antiserum gave 20% and vWD type IIa gave 50% of the rate
of adhesion obtained with normal, hemophilia A, or hemophilia A with
inhibitor plasma, but the same percent adhesion was found with all plasmas.
The rate of adhesion of both vWD type I and type IIa was corrected by the
addition of purified FVIII complex. These results indicated that the
FVIIIR:Ag and not the factor VIII coagulant activity (FVIII:C) in normal
plasma or purified FVIII complex caused an accelerating effect on the rate
at which FWP bound to collagen. Collagen fibrils not only bound FWP, but
also adsorbed the FVIII complex with preferential adsorption of the forms
of FVIIIR:Ag with the greatest ristocetin cofactor (FVIIIR:RCoF) activity.
Saturation of collagen with FWP did not change the adsorption pattern of
the FVIII complex. Also anti-FVIIIR:Ag blocked the accelerating effect of
the FVIII complex but not the adhesion of FWP. Thus, FWP and FVIIIR:Ag
appeared to bind to separate sites on collagen.
Volume 63,
Issue 3,
pp. 495-501,
03/01/1984
Copyright © 1984 by The American Society of Hematology
