The immunosuppressive protein PD-L1 and its potential application in dendritic cell-based immunotherapy

Vaccines based on dendritic cells (DC), the professional antigen-presenting cells of the immune system, can be applied for the treatment of infectious diseases and cancer. A potential problem in the stimulation of antigen-specific T cells is the existence of tolerogenic mechanisms. In this regard, the PD-1/PD-L1 pathway plays an important role. PD-1, expressed on T cells, and up-regulated in chronic infections, signals to down-regulate T cell responses. Tumor cells and DC express PD-L1, which interacts with PD-1, hence tolerizing T cells. Inhibition of this pathway can reactivate T cells. Here, we will evaluate different methods to interfere with this pathway and as such to (re-)boost the T cell response.