Subpopulation Composition and Activation of T Lymphocytes during Coculturing with Mesenchymal Stromal Cells in Medium with Different O2 Content

The concentration of O-2 during coculturing practically did not affect the subpopulation composition of T lymphocytes (CD3(+)/CD4(+), CD3(+)/CD8(+), CD3(+)/CD16(+)/CD56(+) T cells) under conditions of PHA-induced activation. Coculturing with mesenchymal stromal cells (MSC) led to a significant decrease in the ratio of lymphocytes carrying activation markers (CD3(+)/CD25(+) and CD3(+)/HLA-DR+) and increase in the number of CD3(+)/CD16(+)/CD56(+) T cells. The percent of activated HLA-DR+ T cells in a heterotypic culture with MSC at 5% O-2 was much lower than that observed under normal conditions of culturing (20% O-2). Our results suggest that antigen presentation by T lymphocytes due to HLA-DR expression can be reduced in the target tissues at low concentration of O-2, while the interaction between allogeneic MSC probably contributes to more significant inhibition of the immune response.