The number of infiltrating CD8+ lymphocytes were significantly higher in HLA‐DR positive PDA tissues than in HLA‐DR negative PDA tissues (HLA‐DR negative: mean n = 226 ± 51 vs. HLA‐DR positive: mean n = 361 ± 39, P = 0.042; Fig. 2C). Here, CD8A is linked to Patent ductus arteriosus.