Bleeding and isolated thrombocytopenia in idiopathic thrombocytopenic purpura (ITP) are phenomena of a transient or long-term disturbed immune response. Since 1980, ITP has become a model for targeted therapeutic immunomodulation with still unclear mechanisms of action. The systematic analysis of ITP aims to determine more clearly defined patient subgroups for targeted therapy and to explore the complex immune disturbances in this autoimmune disorder. Pediatr Blood Cancer 2006;47:685–686. © 2006 Wiley-Liss, Inc.