Agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia.
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.
Panzer
Simon
S
Clinic for Blood Group Serology, Medical University of Vienna, Vienna, Austria. simon.panzer@meduniwien.ac.at
Höcker
Lisa
L
Rieger
Miriam
M
Vormittag
Rainer
R
Koren
Daniela
D
Dunkler
Daniela
D
Pabinger
Ingrid
I
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*
D000906:Antibodies