The role of cytokines on CD8 T cell memory formation
Short-term initial antigen contact is known to trigger an instructive developmental program by which naive CD8 T cells divide autonomously and differentiate into effector and memory CD8 T cells. However, the factors that regulate the quantity and quality of memory CD8 T cell development are not well understood. Here we showed that short-term exposure of cytokines such as IL-6 and IL-12 during initial antigen contact allows in vitro-activated CD8 T cells to become memory CD8 T cells in larger numbers after adoptive transfer. This effect was attributed to increasing the initial burst size of effector cells through inhibiting their apoptotic death, but not promoting cell division. In addition, these cytokines exposed upon initial antigen contact improved the intrinsic survival and proliferative properties of memory CD8 T cells, contributing to the long-term maintenance. Our results suggest that cytokines can serve as a critical regulatory factor in driving the instructive developmental process from naive to memory CD8 T cells and modulate this process quantitatively and qualitatively.