MDMs (CD11b+HLA-DR++CD206++CD169+CD163+) are the primary cell type in BAL fluid from IPF subjects compared to normal subjects (Fig 1B and 1C); however, RAMs (CD11b+HLA-DR++CD206++CD169+CD163++) are more prevalent in normal subjects compared with IPF subjects. Here, MRC1 is linked to idiopathic pulmonary fibrosis.