CD4 and pulmonary arterial hypertension: According to SOCS3 promoter hypomethylation in CD4+ T cells and upregulation of mRNA levels in PBMCs (Fig. 5), we found that SOCS3 protein levels were significantly higher in PAH patients vs. CTRLs (Fig. 6B), with no difference between IPAH vs. Associated-PAH (two-tailed t-test; p < 0.05).