Summary
Treatment of bleeding in patients with Glanzmann’s thrombasthenia (GT) can be hampered
by iso-antibodies against the αIIbβ3 integrin, which cause rapid clearance of transfused
donor platelets. Type 1 GT patients with a total absence of αIIbβ3 from the platelet
surface are known to be susceptible to form such isoantibodies. In this study, we
describe a type 1 GT patient with a missense mutation (Gly540Asn) located in the EGF3 domain of the β3 integrin subunit. Cotransfection analysis
in CHO cells demonstrates total absence of αIIbβ3 from the surface, based on inappropriate
αIIb maturation. The patient’s serum was reactive with αIIbβ3 and αvβ3 integrins in
a capture assay, when platelets and endothelial cells were used. Two specificities
could be isolated from the patient’s serum, anti-αIIbβ3 and anti-αvβ3 isoantibodies.
Both specificities did not interfere with platelet aggregation. In contrast, isoantibodies
against αvβ3, but not against αIIbβ3, were able to disturb endothelial cell adhesion
onto vitronectin, triggered endothelial cell apoptosis and interfered with endothelial
tube formation. This intriguing finding may explain more recently observed features
of fetal/neonatal iso-immune thrombocytopenia in children from type 1 GT mothers with
intracranial haemorrhage, which could be related to anti-endothelial activity of the
maternal antibodies. In conclusion, we give evidence that two isoantibody entities
exist in type 1 GT patients, which are unequivocally different, both in an immunological
and functional sense. Further research on the clinical consequences of immunisation
against αvβ3 is required, predominantly in GT patients of childbearing age.
Supplementary Material to this article is available online at www.thrombosis-online.com.
Keywords
Glanzmann’s thrombasthenia - platelet function defect - isoimmunisation - αvβ3