IL-12 priming during initial antigen contact increases generation of effector and memory CD8 T cells by changing properties

Initial antigen contact is known to trigger an instructive developmental program by which naive CD8 T cells differentiate into effector and memory cells. However, it remains to be determined how initial cytokine signals act on the generation of effector and memory CD8 T cells. Here, we demonstrate that IL-12 treatment during initial antigen contact results in the significant increase of both primary and memory CD8 T-cell populations. These quantitative differences were associated with qualitative changes in CD8 T cells directly caused by IL-12. Initial IL-12 priming also improved the intrinsic properties of memory CD8 T cells, leading to better protective immunity and vaccine-induced memory CD8 T-cell responses. Our results suggest that IL-12 is an important regulatory factor for developmental programming of CD8 T cells. Future application of IL-12 priming will be discussed.