[Immune modulatory effects of mesenchymal stem cells on T lymphocytes in mixed lymphocyte culture]

To investigate the features of immune modulatory function derived from the interaction of mesenchymal stem cells (MSC) with T lymphocytes in vitro.

Normal human bone marrow mononuclear cells were isolated by Ficoll-Hypaque density gradient, then ex vivo MSCs were cultured, expanded, and obtained after the third passage. The MSCs were added to the two-way mixed lymphocyte culture (MLC) according to different proportion. On day 3 and 5, proliferation of T lymphocytes in each group of MLC-MSC and ctrl-MLC was measured with MTT colorimetry. The surface phenotypes of T lymphocytes were analyzed by flow cytometry before and after co-culture of MLC with MSC.

MLC added with MSC induced dose- and time-dependent inhibition of T lymphocytes proliferation. CD4(+) T cell subsets were not suppressed so obviously as CD8(+) T cell subsets. CD25 expression of T lymphocytes appeared to be lower in MLC-MSC than in ctrl-MLC. But the CD4(+) CD25(+) double positive cells were evidently increased versus control cultures without MSC. The HLA-DR of activated T lymphocytes was slightly decreased compared to the control.

MSC can significantly suppress T lymphocytes' proliferation, especially CD8(+) T cell subsets (CTL). In addition, it can down-regulate the expression of some special surface marker, such as CD25 and HLA-DR, on the activated T lymphocytes.