Cell intrinsic characteristics of human cord blood naïve CD4T 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 CD4T 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 CD4T cells from umbilical cord blood (UCB) and adult peripheral blood. Our data demonstrate naïve CD4T cells from UCB differ from adult naïve CD4T 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 CD4T cells to produce higher levels of IFN-γ and IL-5 compared to adult CD4T cells, respectively. These data demonstrate intrinsic differences between UCB and adult naive CD4T cells and suggest that human perinatal immune responses involve more complex mechanisms than the previously thought Th2-dominant responses.