To further analyze the possible mechanisms responsible for differences in the number of immune cells in the peripheral blood of SSC-PAH and explore the role of inflammation and immune dysregulation in the development and/or progression of IPAH, we analyzed the top 5 most enriched KEGG pathways of those 15 IRGs, which are PD-L1 expression and PD-1 checkpoint pathway in cancer, NF-kappa B signaling pathway, T-cell receptor signaling pathway, and FoxO signaling pathway. Here, CD274 is linked to pulmonary arterial hypertension.