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. 2021 Feb 8;11:614667. doi: 10.3389/fimmu.2020.614667

Figure 2.

Figure 2

Interleukin 15 (IL-15) antagonized the suppression of Tregs to CD8 T cell proliferation and cytotoxic function. CD44hiCD8 T cells from C57BL/6 mice were labeled with CFSE (5 µM) and then incubated with irradiated antigen presenting cells, αCD3 (0.5 μg/ml), and natural Tregs at various ratios (of Tregs vs CD8 T cells indicated in the Figure) with or without IL-15 (1 ng/ml). Three days later, cells were analyzed by flow cytometry. (A) Flow cytometric analysis of one representative experiment from four independent experiments. The absolute numbers and percentages of dividing CD8 T cells in total gated live cells were indicated. (B) IL-15 diminished the suppressor function of Tregs to CD8 T cell proliferation. The suppressor function of Tregs was normalized by CD8 T cell proliferation without the presence of Tregs (n = 4 independent experiments). (C) IL-15 promoted cytotoxic CD8 T cell function under the presence of Tregs. Supernatants collected from (B) were used to measure IFN-γ production by ELISA. Error bars represent standard errors (B) or standard deviations (C). *p < 0.05, **p < 0.01 and ***p < 0.001 by t-test.