Fig. 2: Neonatal mice have higher IL-2 levels and IL-2 receptors than the adult mice.

a Adult and neonatal mice were immunized with PPS14-TT and splenocytes were analyzed for IL-2 expression 7 dpi by FACS. Representative contour plots depict the percentages of IL-2-expressing FoxP3⁺ and FoxP3⁻ cells on T_FH cells. Mean percentages of IL-2⁺ cells among T_FH cells are plotted (n = 5). b, c Splenocytes were analyzed for IL-2 receptor expression 7 dpi by FACS. Representative contour plots depict percentages of IL-2Rα- (b) or IL-2Rβ- (c) expressing FoxP3⁺ and FoxP3⁻ cells on T_FH cells. Mean percentages of IL-2Rα⁺ and IL-2Rβ⁺ cells among T_FH cells are also plotted (n = 5). d Splenocytes from 7 dpi were stimulated with or without recombinant IL-2 for 15 min, followed by intracellular staining for p-STAT5. Representative contour plots depict the percentages of p-STAT5⁺ cells among FoxP3⁺ and FoxP3⁻ T_FH (pre-gated on CD4⁺CXCR5^hiPD-1^hi) cells. Mean percentages of p-STAT5⁺ cells among T_FH cells are plotted (n = 5). The data are representative of at least two independent experiments. Each experiment was performed twice. Unpaired student’s t-test and One-Way ANOVA were used for all comparisons; data represented as mean ± SEM are shown. P values < 0.05 were considered statistically significant. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 and ns (non-significant).