title: Agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia.
abstract: OBJECTIVE
  There are only few studies on agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia (cAITP).
  
  
  METHODS
  We compared agonist (TRAP-6, ADP, Arachidonic acid, Epinephrine, and Ristocetin) -inducible P-selectin expression and PAC-1 binding in 40 patients with cAITP (f/m ratio 23/17) with those in 20 healthy controls. Results were correlated with platelet counts, detectable platelet antibodies, and reticulated platelets.
  
  
  RESULTS
  The in vivo activation of platelets determined the in vitro inducible response to agonists. The stronger the in vivo activation the less the number of platelets responding to agonists, as illustrated by the inverse correlation of P-selectin expression ex vivo and the relative increase after the exogenous addition of agonists. The agonist-inducible platelet activation was not associated with the presence of detectable platelet antibodies to GPIb/IX or GPIIb/IIIa. Agonist-inducible platelet activation was also not correlated with counts of reticulated platelets.
  
  
  CONCLUSIONS
  Agonist-inducible activation of platelets in cAITP is affected mainly by their in vivo activation.
authors.affiliation: Clinic for Blood Group Serology, Medical University of Vienna, Vienna, Austria. simon.panzer@meduniwien.ac.at
authors.forename: Simon
authors.initials: S
authors.lastname: Panzer
authors.forename: Lisa
authors.initials: L
authors.lastname: Höcker
authors.forename: Miriam
authors.initials: M
authors.lastname: Rieger
authors.forename: Rainer
authors.initials: R
authors.lastname: Vormittag
authors.forename: Daniela
authors.initials: D
authors.lastname: Koren
authors.forename: Daniela
authors.initials: D
authors.lastname: Dunkler
authors.forename: Ingrid
authors.initials: I
authors.lastname: Pabinger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood; D001792:Blood Platelets / Q000166:cytology / Q000276:immunology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects; D010976:Platelet Count; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood*
chemical_list: D000906:Antibodies