CCR4 and idiopathic pulmonary fibrosis: Fig 6B shows detectable chemokine genes with differential expression between subsets of IPF patients. We found that CCL17 was primarily produced by MHC class II high macrophages and was higher in the Myeloid-enriched IPF subset. CCR4 is the receptor for CCL17 and is expressed by helper T cells, which may account for the increased numbers of T helper cells in the Myeloid-enriched IPF subset of patients (Fig 4B). CCL15 was primarily produced by ciliated epithelial cells, and was accordingly higher in the Ciliated epithelium-enriched IPF subset (Fig 6B).