Immune mediated thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized 
by production of auto-antibodies against platelet antigens. It is obvious that regulatory T cells 
(Tregs) have a major role in controlling immune homeostasis and preventing autoimmunity. 
To investigate the frequency of Tregs, twenty newly diagnosed, twenty chronic ITP children 
and twenty age and sex matched healthy controls were recruited. The peripheral blood 
mononuclear cells were isolated and the proportion of Tregs was defined by flow cytometry 
method. Results showed that the frequency of Tregs significantly decreased in newly 
diagnosed and chronic ITP patients compared to those in healthy controls. It could be 
concluded that Tregs might play a role in the pathogenesis of ITP.