Sada et al. [25] concluded in a study of Treg cells in iPAH patients that CTLA-4 expression levels in the immunosuppressive CD4CD45RA+-FoxP3high aTregs (aTregs) and CD4CD45RA+-FoxP3low non-Tregs (non-Tregs) subgroups were higher than those in control patients; however, the level of aTregs subgroup in iPAH patients did not change when compared with healthy patients, and the level of non-Tregs subgroup was higher than in healthy patients [25]. Here, CTLA4 is linked to idiopathic pulmonary arterial hypertension.