IL-7 promotes the maintenance of CD31 expression on both adult and CB naive CD4 T cells through the PI3K pathway. (A) CD31 MFI on CD31⁺ and CD31⁻ sorted subpopulations of naive CD4⁺ T cells from adult (n = 13) and CB (n = 5) at day 0 and day 7 in the presence or absence (control) of IL-7. Analysis of CB subsets cultured in the absence of IL-7 was precluded by the high rate of cell death. (B) Longitudinal analysis of CD31 MFI of adult naive CD4⁺ subsets cultured in the presence of IL-7, IL-2, or medium alone (control) for up to 13 days (data representative of 3 individuals). Open symbols represent CD31⁺ purified cells while closed symbols correspond to the CD31⁻ fraction. (C) CD31 MFI assessed on purified CD31⁺ naive CD4⁺ T cells at day 0 and after 7-day culture in the presence of IL-7 alone or in addition to LY294002, PD98059, or DMSO. Each symbol represents one individual. Filled symbols refer to individuals with a proliferative response to IL-7 and open symbols to those that did not proliferate. (D) CD38 MFI are shown in the same culture conditions in adult (n = 6) and CB (n = 4) samples, respectively. Bars represent mean values plus or minus SEM.