PD-1 regulates immunity by binding to PD-L1/PD-L2 on tumor and myeloid cells, suppressing T-cell activation, especially under inflammatory stimuli like INF-γ, IL-1α, or IL-27 (75–77) and hypoxia by hypoxia-inducible factor-1α (HIF-1α) (78–80). The gene discussed is HIF1A; the disease is neoplasm.