All of these PDA-enriched T cell populations shared a striking characteristic which is the absence of all four co-stimulatory immune checkpoint receptors, ICOS, GITR, OX40 and 4-1BB (Figures 2H, 3D–H, Supplemental Figure 3F), suggesting T cell anergy. The gene discussed is TNFRSF4; the disease is Patent ductus arteriosus.