Among the T cell subtypes, CD4 naive T cells (p = 0.049), exhausted T cells (p = 0.0046) and central memory T cells (p = 0.0031) occurred at higher levels in the IPAH group than in the control group, whereas the levels of cytotoxic T cells (p = 0.01), type 17 T helper cells (p = 0.03), effector memory T cells (p = 0.049), natural killer T (NKT) cells (p = 0.01), gamma-delta T cells (p = 0.03), and CD8 T cells (p = 0.01) were higher in the control group. Here, CD4 is linked to idiopathic pulmonary arterial hypertension.