Plasmacytoid dendritic cells are a unique dendritic cell subset that bridges innate and adaptive immune responses. They release high amounts of type I interferons in response to viral and bacterial infection. Plasmacytoid dendritic cells are thought to act as key players in renal allograft rejection, but the underlying mechanisms are unclear. Ruben et al. now demonstrate that granulocyte/macrophage colony-stimulating factor produced by renal epithelial cells is important to induce plasmacytoid dendritic cell maturation and indirect antigen presentation triggering allogeneic immune responses.