PMA INDUCES PLATELET ACTIVATION OF SPECIFIC ANTIGENS (CD62 CD63) IN GPIIB-IIIA DEFICIENT PLATELETS FROM GLANZMANNS-THROMBASTHENIA/

Glanzmann's thrombasthenia (GT) is a hereditary platelet disorder resu lting from a quantitative or qualitative deficiency of the major plate let membrane complex GPIIb-IIIa (CD41) required for platelet aggregati on, We investigated by flow cytometry, the expression of CD41, fibrino gen, and of two platelet activation-related antigens, CD62 and CD63, ( i) before and after activation of platelets by PMA, and (ii) on the su rface and within the cytoplasm of resting platelets, after permeabiliz ation by saponin, Platelets from a series of normal subjects and from nine members of two GT families, were reacted with FITC-conjugated ant ibodies and analyzed on a pow cytometer, Fluorescence intensities meas ured on normal and GT platelets were quantified by using calibrated be ads, Results showed lack of both GPIIb-IIIa and fibrinogen, on the pla telet surface and also within the cytoplasm in five of these GT patien ts, whereas GPIIb-IIIa and fibrinogen remained normal in the four othe r cases. However, CD62 and CD63 antigenic levels were found within nor mal range for all members of these families, after PMA stimulation and also after platelet permeabilization, This work therefore showed that the lack of CD41 in GT, which causes strong disturbance of platelet a ggregation, may not be associated with the deficiency of activation pa thways.