CD8+ T cells (p = 0.037), CD4+ memory resting T cells (p = 0.046), γ delta T cells (p = 0.002), M1 macrophages (p = 0.007), and resting mast cells (p = 0.022) were upregulated in IPAH samples, while CD4+ naive T cells (p = 0.002), resting NK cells (p = 0.013), monocytes (p < 0.001), M0 macrophages (p = 0.045), activated mast cells (p = 0.048), and neutrophils (p < 0.001) were downregulated in IPAH samples. The gene discussed is CD4; the disease is idiopathic pulmonary arterial hypertension.