FIG. 1.

Natural killer (NK) activity regulation by combinatory cell-based immune modulation (CCIM) with mesenchymal stem cells (MSCs) and regulatory T cells (Tregs). (A) Cytolytic activity of NK cells was evaluated by chromium release assay of labeled target Yac-1 cells in the presence of different ratios of effector cells (NK cells). NK cells isolated from BALB/c mice were cultured with irradiated MSCs or Tregs or MSCs plus Tregs before incubation with ⁵¹Cr-labeled Yac-1 tumor targets. Results of the chromium release assay are represented as the means±SEM of triplicate wells from one representative of three experiments. (B) Incubation of NK cells with MSCs or Tregs or MSCs plus Tregs for 48 h. After staining of cells with annexin V-propidium iodide (PI), apoptotic cells (annexin V⁺/PI⁻ and annexin V⁺/PI⁺ cells) were analyzed as a dot plot using a flow cytometer. The numbers in the quadrants of each plot indicate the percentage of annexin-positive (apoptotic) NK cells. The figures are representative of three replicates. *P<0.05.