Costimulation of platelets with rhTPO: TAR patient versus healthy control. Platelets of TAR patient no. 1 (A and C) and of a healthy control (B and D) were stimulated with either ADP (50 μmol/L; A and B) or TRAP (5 μmol/l; C and D) with or without preincubation with rhTPO (20 ng/mL). Flow cytometric analysis of platelet activation was performed using a MoAb against CD62P. CD62P expression of unstimulated platelets as well as the isotype control (dotted line) are shown in each histogram.