Aggregation to thrombin and collagen of platelets from a Glanzmann thrombasthenic patient lacking glycoproteins IIb and IIIa

L McGregor, M Hanss, A Sayegh… - Thrombosis and …, 1989 - thieme-connect.com
L McGregor, M Hanss, A Sayegh, JJ Calvette, MC Trzeciak, D Ville, B Catimel, JJ Viala…
Thrombosis and haemostasis, 1989thieme-connect.com
The aim of this study was to investigate the platelets of a Glanzmann thrombasthenic patient,
which in citrated PRP failed to respond to various agonists, but aggregated and secreted to
high concentrations of thrombin (0.36, 0.72 and 1 U/ml) and collagen (4, 10 and 20 μg/ml)
when washed and resuspended in a Tyrode-albumin solution (containing 2 mM Ca 2+).
Aggregation of the patient platelets was not affected by anti-IIb/IIIa monoclonal antibody
(P18) which strongly inhibits thrombin or collagen induced aggregation of normal platelets …
The aim of this study was to investigate the platelets of a Glanzmann thrombasthenic patient, which in citrated PRP failed to respond to various agonists, but aggregated and secreted to high concentrations of thrombin (0.36, 0.72 and 1 U/ml) and collagen (4, 10 and 20 μg/ml) when washed and resuspended in a Tyrode-albumin solution (containing 2 mM Ca2+). Aggregation of the patient platelets was not affected by anti-IIb/IIIa monoclonal antibody (P18) which strongly inhibits thrombin or collagen induced aggregation of normal platelets. Washed platelets of this patient did not aggregate to ADP (10-100 μM) in the presence of added fibrinogen (2 mg/ml) nor bind 125I-labelled fibrinogen (40 to 320 μg/ml) when thrombin-stimulated. Different anti-IIb/IIIa monoclonal antibodies (P2, P18) when used in binding or crossed immunoelectrophoretic studies showed a complete absence of the IIb-IIIa glycoprotein complex on the patient platelets. Moreover, glycoproteins IIb or IIIa were absent on silver-stained twodimensional (non-reduced/reduced) polyacrylamide gel separations of the patient platelets and were not detected by Western blots used in combination with anti-PLA1 (antigen present on Ilia), anti-Leka (antigen present on IIb). This study shows that platelets lacking glycoproteins IIb or IIIa can aggregate in response to high concentrations of collagen or thrombin when resuspended in the presence of physiological concentrations of calcium. Results obtained in this study could indicate the existence of other mechanisms (other than the IIb-IIIa glycoprotein complex) involving glycolipids, heparans, proteoglycans, and/or unknown membrane glycoproteins to mediate platelet aggregation of stimulated thrombasthenic platelets.
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