Fig. 6: IL-2 production during cell cycle arrest drives enhanced CD8⁺ T cell proliferation.

a, Percentage of IL-2-producing cells (mean ± s.e.m.) among unstimulated IFNγ⁺ mouse CD8⁺ T cells, or ex vivo-stimulated IFNγ⁺ mouse CD8⁺ T cells that were left untreated (non-arrested), arrested in the cell cycle using HU or released from HU-induced arrest (n = 5 mice). b, gMFI (± s.e.m.) of IL-2 in IL-2⁺IFNγ⁺ mouse CD8⁺ T cells under the same conditions as in a (n = 5 mice). c, IL-2 concentration (mean ± s.e.m.) in supernatants of unstimulated mouse CD8⁺ T cells, or ex vivo-stimulated mouse CD8⁺ T cells that were non-arrested, HU-arrested or released from HU-induced arrest (n = 5 mice). d, Representative flow cytometry plots of ex vivo-stimulated IL-2^GFP+ CD8⁺ T cells from IL-2^GFP reporter mice under ex vivo-stimulated conditions (HU-arrested, non-arrested and released). e, Percentage of IL-2^GFP+ CD8⁺ T cells (mean ± s.e.m.) under the same conditions as in d and in unstimulated conditions (n = 3 mice). f, IL-2^GFP reporter mice were vaccinated with E7 SLP/CpG and treated with HU for 4 consecutive days (days 1–4). IL-2^GFP expression (gMFI ± s.e.m.) was measured in E7_49–57-specific CD8⁺ T cells from spleens at days 5 and 8 after vaccination (n = 3 mice). g, Representative histograms of CD25 expression in mouse and human CD8⁺ T cells that were unstimulated or ex vivo-stimulated and non-arrested, HU-arrested or released. h, Representative flow cytometry plots of CellTrace Violet versus CD25 expression of HU-arrested, non-arrested and released mouse and human CD8⁺ T cells ex vivo. i, Representative CellTrace Violet plots of mouse CD8⁺ T cells under the same conditions as in g, with IL-2-neutralizing antibodies (S4B6 and JES6.1) added during proliferation. j, Percentage of proliferating CD8⁺ T cells (mean ± s.e.m.) from WT and IL-2^fl/fl mice that were ex vivo stimulated and released from HU arrest. IL-2 was supplemented during proliferation (n = 5 WT mice, n = 4 IL-2^fl/fl mice). k, pSTAT5 levels (gMFI ± s.e.m.) in mouse CD8⁺ T cells under the same conditions as in i (n = 5 mice). l, Percentage of proliferating cells (left) and CD25 expression (right; gMFI ± s.e.m.) of ex vivo-stimulated human CD8⁺ T cells (non-arrested and HU-released) with or without addition of STAT5-IN-1 supplemented during proliferation (n = 3 donors). Statistical comparisons were determined by repeated-measures ANOVA with Sidak’s multiple comparisons (a–c, e, f, j and k); P values are shown on the graphs.