To obtain more comprehensive insight, we performed a PCA and found that IPAH patients at diagnosis and at 1-year follow-up were separated in Dim2 (21.5%) and Dim3 (9.5%), to which Th and Tc subsets, IFNγ+ T cells and CTLA4 contributed most (Figure 5A). Here, CTLA4 is linked to idiopathic pulmonary arterial hypertension.