RESUMEN
<p><b>OBJECTIVE</b>To study the immunocharacteristics of bone marrow mesenchymal stem cell (MSC) and provide experimental evidence for the potential therapeutic application.</p><p><b>METHODS</b>MSCs were isolated from rat bone marrow and confirmed by immunophenotype, and the growth dynamic and cell cycle were analyzed. MSCs were cultured with or without 200 U/ml interferon gamma (IFNg) , the expression of PDL-1, CD54, CD40, CD80, CD86, MHC-I, and MHC-II was detected by flow cytometry. MSCs were used as regulatory cells in mixed lymphocyte reaction (MLR), the PDL-1 and CD54 molecules on MSCs were blocked to explore their roles in MLR. The IFN, IL-2, IL-4 and IL-10 molecules in culture supernatant were quantified by ELISA. The homing of MSCs to liver and induction of microchimerism were analyzed after MSCs transplantation.</p><p><b>RESULTS</b>The purity of MSCs was high. The growth curve showed that the first two days were the lag phase; the third, fourth, fifth days were the log phase; the sixth and seventh days were the stationary phase. Flow cytometry indicated that 76.0%+/-2.0% of the MSCs were in G1/G0 phase, 13.0%+/-2.0% in S phase, 10.0%+/-1.7% in G2 and M phase. IFNg treatment led to up-regulation of CD54, PDL-1, MHC-I and MHC-II, however, CD40, CD80 and CD86 were not expressed on MSCs even after IFNg treatment. MSCs inhibited MLR, IFNg treatment enhanced the inhibitory effect of MSCs on MLR. Blocking of PDL-1 or CD54 on MSCs partially alleviated the inhibition effect. There were high levels of IFNg and IL-10, and low level of IL-4 in the culture supernatant of MLR, however, IL-2 was not detected. MSCs can home to the liver and induce formation of microchimerism after transplantation.</p><p><b>CONCLUSION</b>IFNg treatment enhances the inhibitory effect of MSCs on MLR, PDL-1 and CD54 are key molecules mediating this inhibitory effect. MSC can home to the liver and induce formation of microchimerism after transplantation.</p>