The pattern of GPIIIa peptides that stimulate PBMCs from patients with AITP to proliferate can evolve over time. Proliferative responses of PBMCs from a representative patient (AITP22) against the panel of 86 peptides spanning the GPIIIa molecule were compared on 3 different occasions, at presentation (A; platelet count 76 × 109/L), then after 44 weeks (B; platelet count 54 × 109/L), and 56 weeks (C; platelet count 84 × 109/L). The dashed horizontal line denotes the level of proliferation taken as representing a significant positive response (SI > 3).