According to GSEA analysis (Figure 3), most genes in PAH samples with low ACKR4 were enriched in the following biological process: leukocyte migration, MAPK cascade, negative regulation of apoptotic, negative regulation of cAMP-mediated signaling, positive regulation of fibroblast proliferation and regulation of lymphocyte activation. The gene discussed is ACKR4; the disease is pulmonary arterial hypertension.