Pretreatment of activated human CD8 T cells with IL-12 leads to enhanced TCR-induced signaling and cytokine production

During the immune response to pathogens and autoantigens, CD8T cells are exposed to numerous inflammatory agents including the cytokine IL-12. Previous studies have focused on how IL-12 regulates T cell functions when present during or after the activation of the T cell receptor (TCR). However, recent studies suggest that prior exposure to IL-12 also alters the TCR responsiveness of murine T cells. Whether similar phenomena occur in human activated CD8T cells and the mechanisms mediating these effects remain unexplored. In this study, we observed that pretreatment of human activated CD8T cells with IL-12 results in increased cytokine mRNA and protein production following subsequent TCR challenge. The potentiation of TCR-mediated cytokine release was transient and required low doses of IL-12 for at least 24 h. Mechanistically, prior exposure to IL-12 increased the TCR induced activation of select MAPKs and AKT without altering the activation of more proximal TCR signaling molecules, suggesting that the IL-12 mediated changes in TCR signaling are responsible for the increased production of cytokines. Our data suggest that prior treatment with IL-12 potentiates human CD8T cell responses at sites of infection and inflammation, expanding our understanding of the function of this clinically important cytokine.