Cell intrinsic characteristics of human cord blood naïve CD4Â T cells

It has been generally considered that the perinatal immune system is less inflammatory compared to the adult system and type 2 responses predominate perinatal immune responses against antigens. Indeed, previous studies in mice showed that there are cell-intrinsic differences between neonatal and adult CD4 T cells. However, studies on human cord blood and infant blood demonstrated that human perinatal T cells do not produce elevated levels of Th2 cytokines with the exception of IL-13. These data raise the question if human T cells in the perinatal blood fundamentally differ from adult T cells. To decipher differences between human perinatal and adult T cells, we performed a focused comparative analysis on purified naïve CD4 T cells from umbilical cord blood (UCB) and adult peripheral blood. Our data demonstrate naïve CD4 T cells from UCB differ from adult naïve CD4 T cells in surface expression of CD26, dipeptidyl peptidase-4. While only a fraction of effector/memory T cells from adult blood express CD26, practically all T cells from UCB express high levels of CD26. We also determined that Th1/Th2 polarizing conditions induce UCB CD4 T cells to produce higher levels of IFN-γ and IL-5 compared to adult CD4 T cells, respectively. These data demonstrate intrinsic differences between UCB and adult naive CD4 T cells and suggest that human perinatal immune responses involve more complex mechanisms than the previously thought Th2-dominant responses.