ITP is primarily due to T-cell disturbances and recently, many reports have demonstrated that active ITP is associated with a peripheral deficiency of tolerance-inducing CD4+CD25+FoxP3+ T regulatory cells (Tregs). Tregs are critical in maintaining immune tolerance and deficiencies and/or functional defects in the T-cell subset may be the underlying reason why individuals become autoimmune against their platelets. This session will first give an overview of the immune defects associated with T cells in ITP and then delve into a detailed analysis of how abnormal Tregs may be responsible for the induction of ITP. It will then conclude with an overview of the clinical aspects of ITP with respect to new therapeutic developments and how Tregs are influenced by the various forms of therapy for this sometimes difficult-to-manage disorder.