KIT and idiopathic pulmonary fibrosis: To further delineate the identity of the 15-PGDH+ hematopoietic cells, we fractionated on the basis of CD117 to enrich mast cells, which participate in pulmonary wound healing33, and F4/80 to enrich alveolar macrophages, which are implicated in IPF pathogenesis1 and have also recently been shown to express 15-PGDH32.