We therefore measured PD-1 expression by CD8+ and CD4+ T cells in the blood and tumors of patients with PDA and determined that there was a markedly higher proportion of PD-1+ CD4+ and CD8+ T cells in tumors compared to paired blood samples (p = 0.003 and 0.02, respectively; Figure 5C). The gene discussed is CD8A; the disease is Patent ductus arteriosus.