Objective: Idiopathic thrombocytopenic purpura(ITP)is characterized bya lowplatelet count and mucocutaneous bleeding. The immunity abnormality plays important role in the pathophysiology of idiopathic thrombocytopenic purpura. Mesenchymal stem cells (MSC)have been shown to possess immunosuppressive activity

preventing lymphocytes activiation. The aim of the study was to compare the immunosuppressive activity of MSC from controls and patients with ITP in vitro. Methods: Bone marrow samples were collected from patients with ITP at diagnosis(n=19)

and the patients whose findings of bone marrow aspiration showed normal were established as the controls(n=11). MSCs from bone marrow samples were isolated

cultured and expanded. Morphology

proliferative activity and colony forming unit-fibroblast(CFU-F)were measured and analyzed. MSC were assayed for the activity of lymphocytes suppression by mixed lymphocyte reaction(MLR). The hepatocyte growth factor

transforming growth factor-β1 mRNA expression was detected by RT-PCR. HGF

TGF- β1 release of MSC was tested by ELISA. Results:(1)The culture cells from the patients with ITP presented a typical fibroblast-like morphology. The numbers of CFU-F from the patients with ITP (21.29±5.25)showed no difference from the controls (22.33±5.33)

P>0.05. (2)The inhibition ratio ofMSC in patients with ITP (74.93±8.01)% showed no difference from that in the controls(76.42±8.80)%

P>0.05;(3)The TGF- β1

HGF mRNA expression in MSC in patients with ITP were similar to those in the controls

P>0.05;(4)The concentration of TGF- β1 in MSC supernatants in the patients with ITP(617.88±81.89)pg/ml was similar to that in the controls (632.40 ±126.90)pg/ml

P >0.05;the concentration of HGF in MSC supernatants in the patients with ITP (520.20±60.67)pg/ml was similar to that in the controls (521.56±36.72)pg/ml

P>0.05. Conclusion: The suppressive effect of MSC on patients with ITP in vitro showed no difference from that on the controls.