[The role of miR-155 in pathogenesis of immune thrombocytopenia].

OBJECTIVE: To explore the role of microRNA-155 (miR-155) in pathogenesis of immune thrombocytopenia (ITP) through investigate the relevance between the expression of miR-155 in CD19(+) B cells in peripheral blood and the function of B lymphocytes in patients with ITP.

METHODS: A total of 55 ITP patients (30 newly diagnosed and 25 in remission) were collected from December 2014 to October 2015 in Tianjin Medical University General Hospital, and 25 healthy volunteers were recruited as controls. The CD19(+) B cells were extracted by immunomagnetic microbeads. The expression of miR-155 in CD19(+) B cells were detected by real-time fluorescent quantitative PCR. The levels of IgG, IgM and SH2 domain-containing inositol 5'-phosphatase 1 (SHIP-1) in CD19(+) B cells were measured by flow cytometry (FCM). Correlation between miR-155 and clinical parameters of ITP patients was analyzed.

RESULTS: (1) The expression of miR-155 in CD19(+) B cells in newly diagnosed ITP patients (4.57±1.03) was significantly higher than that in remitted ITP patients (0.79±0.13) and controls (1.74±0.32), and that in the remitted ITP patients was lower than in the controls (all P<0.05). In addition, the level of miR-155 at initial diagnosis in the patients responding to treatment (3.85±0.71) was lower than that in the refractory patients (6.67±1.05) (P<0.05). (2) The levels of IgG and IgM in CD19(+) B cells in newly diagnosed ITP patients (35.20%±6.19%, 26.87%±5.01%) were significantly higher than those in remitted ITP patients (7.51%±1.91%, 5.93%±2.23%) and controls (8.23%±0.68%, 8.21%±1.08%) (all P<0.05). (3) The expression of SHIP-1 in CD19(+) B cells in newly diagnosed ITP patients (44.33%±3.95%) was significantly lower than that in remitted ITP patients (83.13%±3.24%) and controls (67.26%±3.73%), and that in the remitted ITP patients was higher than in controls (all P<0.05). (4) The expression level of miR-155 in CD19(+) B cells in ITP patients was positively correlated with CD19(+) CD5(+) B cell count (r=0.576, P<0.05), and negatively correlated with the level of SHIP-1 and peripheral platelet count (r=-0.445, -0.402, all P<0.05).

CONCLUSION: There is abnormally high expression of miR-155 in CD19(+) B cells in peripheral blood of ITP patients, which is related with the dysfunction of B lymphocytes and ntracellular antibody production, suggesting that miR-155 might be involved in the pathogenesis of ITP.