CpG and Interleukin-15 Synergize to Enhance IFN-γ Production by Activated CD8⁺ T Cells

Figure 4

Synergy between IL-12 and IL-15 overcomes potent suppression of CD8⁺ T-cell responses by nTreg. (a) CFSE-labeled CD8⁺ T cells, APC, and anti-CD3 were cultured in the absence or presence of purified nTreg at a 1 : 1 or 1 : 2 Treg : CD8 T-cell ratio, along with either IL-12, IL-15, or IL-12+IL-15. After 72 hours, cells were analyzed for CFSE dilution by FACS. 30,000 live events were collected, percentages reflect the number of CFSE^lo, or dividing CD8⁺ T cells (***𝑃<0.001, **𝑃<0.01). (b) 30,000 CD8⁺ T cells were analyzed to determine the frequency of CD8⁺ T cells that had divided either 1–3 or >4 times. Numbers reflect the percentage of cells accumulated in either group. 𝑃 values for cytokine-treated wells are relative to Treg suppression controls (no cytokines). **𝑃<0.01 for IL-12+IL-15 relative to IL-12; *𝑃<0.05 for IL-12+IL-15 relative to IL-12. In (c), supernatants were harvested from cocultures and analyzed for IFN-𝛾 by ELISA (***𝑃<0.001, **𝑃<0.01). Results of one experiment are shown, asterisks represent the statistical significance of each group from at least 4 experiments.

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