Identification of glycoprotein Ib as a target for autoantibody in
idiopathic (autoimmune) thrombocytopenic purpura
NS Szatkowski, TJ Kunicki and RH Aster
An antibody (DIL) from a patient with idiopathic thrombocytopenic purpura
(ITP) was shown to have autospecificity on the basis of reactions with
autologous platelets that were identical to those obtained with platelets
from normal subjects. DIL antibody also reacted strongly in an
immunofluorescence test with platelets from a patient with Glanzmann's
thrombasthenia, but failed to react with platelets from a patient with the
Bernard-Soulier syndrome who was known to be deficient in glycoprotein Ib
(GPIb). Purified GPIb and control platelets, but not Bernard-Soulier
platelets, inhibited the lytic activity of DIL. Using the GPIb-specific
monoclonal antibody AP1 and one-dimensional rocket electrophoresis into
gels containing rabbit antihuman platelet membrane antibody, it was shown
that staphylococcal protein A-Sepharose beads coated with DIL antibody
selectively remove GPIb from solubilized platelet preparations. By crossed
immunoelectrophoresis it was found that DIL recognizes a determinant on
GPIb on the membrane side of the cleavage site of the platelet calcium-
activated protease (calpain). These studies provide direct evidence for
binding of a platelet autoantibody to a determinant on GPIb relatively
close to the site of insertion of this protein into the platelet membrane.
Volume 67,
Issue 2,
pp. 310-315,
02/01/1986
Copyright © 1986 by The American Society of Hematology
