An aberrant co-inhibitory signal 2 is represented by PD-L1/PD-1 pathway activation since recent studies have shown that this axis constitutes a major suppressive mechanism to evade immune activation and tumor clearance by downregulating T cell activation, proliferation, survival, cytotoxicity and cytokine release (Tseng et al., 2001; Dong et al., 2002). The gene discussed is CD274; the disease is neoplasm.