Assessment of Regulatory T Cells in Childhood Immune Thrombocytopenic Purpura

This study had the objective to assess the frequency of Tregs in children newly diagnosed with ITP and ascertain whether an association exists between Tregs and platelet counts, by means of a comparison with healthy controls. This case-control study included 19 patients newly diagnosed with ITP—whose blood samples were collected at four points in time: before any therapy and 1, 3, and 6 months after diagnosis—and 19 healthy controls. Tregs (CD4+ CD25+Foxp3 T cells) were evaluated by flow cytometry. There was a statistically significant difference in platelet count between the case and control groups. There were no significant differences in Treg counts between cases and controls at any point during the course of the study and no difference in Treg counts between the chronic and nonchronic groups and no significant correlation between Tregs and platelet counts in the case and control groups. The findings of this study did not show any statistically significant correlation between Tregs and number of platelets in the case and control groups. Treg cells did not play a role in the regulation of autoimmunity in children with ITP. 1. Introduction Immune thrombocytopenic purpura (ITP) is an immune-mediated hemorrhagic condition that affects approximately 1 in 25,000 children every year [1, 2] and may present both as an acute, self-limiting condition and as a recurrent (chronic) form. ITP is characterized by premature destruction and clearance of platelets by mononuclear phagocytes [3]. Approximately 75% of patients recover spontaneously within 4 to 6 months [4]. Most children with ITP are previously healthy and are in fact the victims of their own imbalanced defenses [5]. Over the last two decades, several investigators have contributed to an improved understanding of the pathophysiology of this condition in an attempt to develop an individualized treatment approach for affected patients. The ability to distinguish between self- and non-self-antigens is known as immune tolerance and plays an essential role in preventing intense self-recognition, which would produce pathological autoimmune responses [6, 7]. The term “peripheral tolerance” refers to mature reactive cells that escaped negative selection in the thymus and are suppressed from peripheral blood by a particular class of immunoregulatory cells, the regulatory T cells (Tregs) [4, 6, 8]. Tregs account for approximately 5% of circulating CD4+ T cells and are characterized by constitutive expression of transcription factor forkhead box protein 3 (Foxp3) molecules and high CD25 levels [9]. Recent studies