PBMCs from healthy control donors rarely proliferate when stimulated with peptides from the GPIIIa sequence. Shown here are proliferative responses of PBMCs from representative healthy control donors C5 (A), C6 (B), C8 (C), and C17 (D) against the panel of 86 peptides spanning the GPIIIa molecule. The dashed horizontal line denotes the level of proliferation taken as representing a significant positive response (SI > 3).