PDGFB and pulmonary arterial hypertension: As strong evidence of the clinical relevance of this work, Pdgfb levels of macrophages differentiated from circulating monocytes of IPAH and SSc-PAH patients were enhanced by 5.1 ± 1.8–fold and 10.7 ± 4.8–fold, respectively, in comparison with those of control humans (Figure 6B and Supplemental Table 4).