For macrophages derived from control patients, hPASMC proliferation was not changed by anti–PDGF-B pretreatment whereas this pretreatment significantly inhibited hPASMC proliferation induced by medium conditioned by IPAH or SSc-PAH macrophages (Figure 6E and Supplemental Figure 9D). This evidence concerns the gene PDGFB and pulmonary arterial hypertension.