A monoclonal antibody directed against a granule membrane glycoprotein (GMP-140/PADGEM, P-selectin, CD62P) inhibits ristocetin-induced platelet aggregation.

Abstract

P-selectin (also called CD62, GMP-140, PADGEM, CD62P) is a recently described member of a family of vascular adhesion receptors expressed by activated platelets and endothelial cells that are involved in leucocyte cell adhesion. The aim of this study was to characterize a new monoclonal antibody (LYP7) directed against activated human blood platelets that inhibits ristocetin-induced platelet aggregation. Immunoadsorbent affinity chromatography and immunoprecipitation studies showed that LYP7 (IgG1) bound a surface-labelled glycoprotein (GP) which changed its apparent molecular mass (M(r)) on reduction from 138 kD (situated below GPIIb) to 148 kD (above GPIIb alpha). LYP7 and S12, a monoclonal antibody directed against P-selectin immunoprecipitated the same band. Using ELISA assay, purified P-selectin was shown to bind LYP7 and S12 monoclonal antibodies. Binding sites of 125I-labelled LYP7, which was greatly increased on thrombin-stimulated (2 U/ml) washed platelets (10825 +/- 2886, mean +/- SD) Kd = 1.5 +/- 0.5 nM) compared to resting platelets (2801 +/- 1278, mean +/- SD) (Kd = 1.5 +/- 0.6 nM), was found to be normal on thrombin-stimulated platelets taken from a patient with grey platelet syndrome or a patient with Glanzmann thrombasthenia. LYP7 (IgG1, F(ab')2 or Fab fragments) inhibited ristocetin-induced platelet aggregation of platelets in a dose-dependent fashion without affecting the binding of von Willebrand (vWf) factor. However, agglutination of formaldehyde-fixed platelets induced by ristocetin was not affected by monoclonal antibody LYP7. In addition, the binding of thrombin-activated platelets to neutrophils was inhibited by monoclonal antibody LYP7. These results strongly suggest that P-selectin, by promoting cell-cell contact, may play an active role in platelet-platelet interactions.

• Authors: H Boukerche, M H Ruchaud-Sparagano, C Rouen, J Brochier, C Kaplan, J L McGregor
• Journal: British journal of haematology (Br J Haematol) Vol. 92 Issue 2 Pg. 442-51 (Feb 1996) ISSN: 0007-1048 [Print] England
• PMID: 8603015 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• P-Selectin
• Ristocetin
• Thrombin

Topics

• Antibodies, Monoclonal (pharmacology)
• Cell Adhesion
• Dose-Response Relationship, Drug
• Electrophoresis, Gel, Two-Dimensional
• Enzyme-Linked Immunosorbent Assay
• Humans
• Neutrophils (physiology)
• P-Selectin (immunology)
• Platelet Activation
• Platelet Aggregation (drug effects)
• Ristocetin (pharmacology)
• Thrombasthenia (blood)
• Thrombin (pharmacology)