Activation response of GPIIbIIIa-deficient platelets to TTS sera. CD41 expression and platelet activation of Glanzmann platelets in response to sera from patients with TTS. (A) CD41 measured on normal platelets and platelets from a patient with Glanzmann thrombasthenia. (B) Patients’ sera containing or lacking platelet autoantibodies with GPIIb/IIIa specificity were incubated with normal platelets and platelets from a patient with Glanzmann thrombasthenia. Platelet activation was assessed by testing PS exposure after annexin-V staining in flow cytometry, cutoff was defined as mean of negative sera (shown in beige).