In our annotations, we refer to SPP1+ macrophages as CHI3L1+ macrophages, resembling previously identified TREM2+ macrophages (36), define the airway macrophage niche (Fig. 2A), which, together with C1Qhi macrophages (36), was nearly exclusively found in IPF tissue (fig. This evidence concerns the gene CHI3L1 and idiopathic pulmonary fibrosis.