Summary
Antibodies directed against the glycoprotein (GP) Ib have been identified as the potential
cause of various platelet disorders: Immune thrombocytopenic purpura (ITP) may be
caused by such autoantibodies; Anti-thrombotic drugs targeting GPIb also induce thrombocytopenia.
In order to elucidate the potential mechanism(s) of the anti-GPIb effects, we have
examined by electron microscopy (EM) the effect of several antibodies directed against
GPIb and GPIIb-IIIa on human culture megakaryocytes (MK). Virtually all antibodies
to GPIb enhanced the interaction of newly formed platelets with MK when compared to
other antibodies. These effects were retrieved when antibodies were tested on platelets.
We conclude that antibodies to GPIb can potentially inhibit platelet release by MK,
and can also induce homotypic platelet adhesion. These results may have implications
in the pathophysiology of thrombocytopenia and platelet recovery in ITP, and shed
light on the pathological effect of anti-GPIb antibodies used as antithrombotic drugs.
Keywords
Megakaryocytes - platelets - GPIb