Summary
Although it is recognized that glycoprotein (GP) IIb-IIIa complexes are deficient
in platelets in Glanzmann’s thrombasthenia, little is known of the origin of the defect.
We have examined the megakaryocytes in a bone marrow aspirate obtained from a thrombasthenia
patient during surgery. Analysis of platelet proteins by SDS-polyacrylamide gel electrophoresis
confirmed the patient to be of the type I subgroup. The megakaryocytes were examined
by immunofluorescence or by immunocytochemical procedures combined with electron microscopy.
Antibodies used included the murine monoclonal antibody, AP-2 and the human allo-antibody,
IgG L, both of which recognize determinants on GP IIb-IIIa complexes. Bound antibody
was detected by anti-IgG antibodies coupled to fluorescein isothiocyanate or adsorbed
on gold particles. In the immunofluorescence studies, permeabilized megakaryocytes
were identified by double staining using an antibody to von Willebrand factor (vWF).
Whereas mature megakaryocytes and their small precursor cells from normal individuals
were strongly fluorescent with AP-2 and IgG L, most vWF positive cells from the Glanzmann’s
thrombasthenia patient were negative and the remainder gave but a weak background
fluorescence. Immunogold staining on the surface of marrow cells was severely reduced.
Our results confirm a deficiency of GP IIb-IIIa complexes in megakaryocytes in thrombasthenia.
Keywords
Platelets - GP IIb-IIIa complexes - Glanzmann’s thrombasthenia
