CD4 and pulmonary arterial hypertension: The Fiddle diagram (Fig 7) revealled significant differences in several immune cell types, including activated CD4 T cells, CD56 bright natural killer cells, eosinophils, gamma delta T cells, immature dendritic cells, mast cells, natural killer T cells, natural killer cells, neutrophils, regulatory T cells, T follicular helper cells, and effector memory CD8 T cells, suggesting their involvement in PAH progression.