Soluble P-selectin is present in normal circulation and its plasma level is elevated in patients with thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome

Br J Haematol. 1993 Aug;84(4):702-10. doi: 10.1111/j.1365-2141.1993.tb03149.x.


P-selectin is an integral membrane glycoprotein stored in the secretory granules of platelets and endothelial cells. To determine whether soluble P-selectin may be present in the circulation of healthy humans, we used a sandwich immunoassay to assess citrated plasma from 50 subjects. P-selectin was present in concentrations ranging from 19 to 521 ng/ml (mean +/- SD = 121 +/- 84 ng/ml). The apparent molecular weight of P-selectin immunoisolated from platelet-poor plasma was similar to that of the detergent-soluble form isolated from platelet membrane. Plasma levels of P-selectin were unaffected by the following procedures: (1) drawing of blood in the presence of protease inhibitors; (2) stimulation of platelet-rich plasma with aggregating agents; (3) ultracentrifugation at 100,000 g for 120 min at 4 degrees C or filtration through a 0.22 micron membrane; or (4) preincubation of platelet-poor plasma with immobilized anti-platelet glycoprotein Ib monoclonal antibodies. It appeared that plasma P-selectin did not result from the in vitro activation of platelets, nor was it derived from platelet microparticles. We also found that plasma P-selectin levels were significantly elevated in patients with thrombotic thrombocytopenic purpura (12 patients, 332 +/- 184 ng/ml, P < 0.001) and haemolytic uraemic syndrome (17 patients, 297 +/- 191 ng/ml, P < 0.0001), as compared to the normal levels. Thus, these data should facilitate the study of the pathophysiological significance of circulating P-selectin.

MeSH terms

  • Adult
  • Antigens, CD / analysis
  • Blood Platelets / chemistry
  • Blood Specimen Collection / methods
  • Female
  • Hemolytic-Uremic Syndrome / blood*
  • Humans
  • Immunoenzyme Techniques
  • Male
  • Middle Aged
  • Molecular Weight
  • P-Selectin
  • Platelet Aggregation / physiology
  • Platelet Membrane Glycoproteins / analysis*
  • Platelet Membrane Glycoproteins / chemistry
  • Purpura, Thrombotic Thrombocytopenic / blood*
  • Solubility


  • Antigens, CD
  • P-Selectin
  • Platelet Membrane Glycoproteins