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). Here, PDGFB is linked to idiopathic pulmonary arterial hypertension.