Objective To investigate the changes of protein kinase C(PKC) activity in peripheral blood T lymphocytes of the children with idiopathic thrombocytopenic purpura (ITP) and the relationships between PKC activity and T lymphocytes activation and thrombocyte decrease.Methods Sterilized peripheral blood were collected from ITP children (n=35) and healthy children (n=30).T lymphocytes were isolated and purified by the T cell segregation enrichment column.The total PKC activity was detected by non-radioactive assay.FasL,the T cell activated marker,was determined by flow cytometer.Platelet count was performed by hematocytometer.Result Compared with healthy children,total PKC activity in ITP children was significantly enhanced (0.97?0.21 nmol/min.ml vs 0.60? 0.13 nmol/min.ml,?s,P