To study the role of PD-1 in angiogenesis development, the relative hindlimb blood perfusions were determined in WT and PD-1-/- mice before surgery, shortly after hindlimb ischemia, and 3, 7, 14, and 21 days after hindlimb ischemia as illustrated in Figure 1A. The gene discussed is PDCD1; the disease is ischemia.