CD4 and Patent ductus arteriosus: In line with the findings, correlation between CD4+ and CD8+ T‐cell infiltration was detected in PDA patients, but not that between CD8+ T‐cell infiltration and Foxp3+ Treg, suggesting the effector CD4+ T cell may infiltrate into the TME of PDA associated with CD8+ T‐cell infiltration, irrespective of Treg infiltration.