IL-7 stimulation leads to STAT5 phosphorylation, Bcl-2 up-regulation, and IL-7Rα down-modulation in both CD31⁺ and CD31⁻ naive CD4⁺ subsets. IL-7Rα expression (A), STAT5 phosphorylation (B), Bcl-2 expression (C), and 7-AAD incorporation (D) were evaluated by flow cytometry within gated CD31⁺ and CD31⁻ naive CD4 subsets. p-STAT5 was assessed on freshly isolated mononuclear cells from adult (n = 5) and CB (n = 3) samples either unstimulated or stimulated with IL-7 for 15 minutes. Bcl-2 and IL-7Rα MFI were evaluated ex vivo in adult PBMC (n = 6 and n = 9, respectively) and CB cells (n = 4 and n = 6, respectively) and in the corresponding purified CD31⁺ and CD31⁻ naive subsets cultured in the presence of IL-7 for 7 days. 7-AAD incorporation was measured in purified CD31⁺ and CD31⁻ subsets after 7 days of culture in the presence of IL-7 and in its absence (control). Bars represent mean MFI values plus or minus SEM.