Mechanism of HLA-G participation in inhibiting lymphocyte proliferation by amniotic mesenchymal stem cells

Abstract

This study was aimed to investigate the inhibitory mechanism of human amniotic mesenchymal stem cells (HAMSC) on lymphocyte proliferation and to validate the participation of the nonclassic human leukocyte antigen (HLA) class I molecule (HLA-G) in immunosuppressive action of HAMSC. HAMSC were isolated from fetal membranes of human placentas, and were cultured and expanded. The phenotypes of HAMSC were identified by flow cytometry, at same time the HLA-G levels on membrane surface and in cytoplasm were detected by flow cytometry. The soluble HLA-G (sHLA-G) level in HAMSC supernatants was determined by ELISA, MTT assay was used to examine the effect of mixed cultured HAMSC on proliferation of lymphocytes. The results showed that both surface and cytoplasm of HAMSC expressed HLA-G, the average rates of HLA-G expression on surface and in cytoplasm were (16.75 ± 3.871)% and (39.14 ± 4.274)%, respectively. The sHLA-G level in cell culture supernatant was 5.2 ng/ml. After HAMSC and culture supernatants were added in the MLR, the inhibitory rate on lymphocyte proliferation increased obviously, meanwhile the inhibitory rate on lymphocyte proliferation decreased when the HLA-G antibody was added in MLR. It is concluded that the surface and cytoplasm of HAMSC express HAL-G, at same time HAMSC secrete the HLA-G to supernatants of culture. The HLA-G is one of critical factors inhibiting immuno-function of HAMSC. This study contributes to improve the clinical therapeutic trails for using the HAMSC to prevent rejection.