In patients with idiopathic PAH, the expression of PD-1/PD-L1 on the surface of peripheral blood CD4+ and CD8+ lymphocytes are significantly upregulated, the proportion of Tregs is increased, and IL-10 secretion is reduced, suggesting that excessive activation of the PD-1/PD-L1 axis synergizes with Treg dysfunction to exacerbate immune dysregulation and affect metabolic homeostasis (Tomaszewski et al., 2024). This evidence concerns the gene PDCD1 and pulmonary arterial hypertension.