To our current knowledge, they are involved in immune response regulation and tumor immune escape; soluble PD-1 blocks the PD-1–PD-L1 interaction and activates CD8+ T cells, while soluble PD-L1 binds to PD-1 with higher affinity than the membrane-bound forms, ultimately inhibiting the T cell response [10,11]. The gene discussed is PDCD1; the disease is neoplasm.