Within the CD4+ T helper lymphocyte compartment patients with IPAH showed elevated subsets of Th2 and regulatory T cells, while the subset of Th1/Th17 lymphocytes was reduced as compared to healthy subjects and as indicated by relative and absolute cell counts (all p < 0.05; two-way rANOVA; Figs. 4 and 5). This evidence concerns the gene CD4 and idiopathic pulmonary arterial hypertension.