Particular dominant peptides from GPIIIa stimulate T cells from many patients with AITP to proliferate. Shown here are the proportions of patients with AITP (▪) and healthy control donors (□) whose PBMCS proliferated in response to each of the 86 peptides from the panel spanning GPIIIa. PBMCS from all persons in both groups responded to stimulation with the control recall antigen mycobacterial PPD (▨).