Inhibitory checkpoint molecules generated upon T cell activation, such as those that regulate the immunological synapses between T cells and dendritic cells in lymph nodes (CTLA-4 and B7.1), or between T cells and tumor cells (PD-1 and PDL-1/2), are currently the most relevant targets for immunotherapy (see Figure 2) [56]. The gene discussed is PDCD1; the disease is neoplasm.