Besides its heme-scavenging signature, C1 was enriched in CCL18 (Fig. 3b and Supplementary Fig. 3c), a chemokine known to be produced by alternatively activated macrophages, inducing fibrosis via crosstalk with fibroblasts in idiopathic pulmonary fibrosis (IPF)22. The gene discussed is CCL18; the disease is idiopathic pulmonary fibrosis.