TGFB1 and idiopathic pulmonary fibrosis: Once we determined that MCEMP1 expression was detected in classical monocytes and alveolar macrophages in IPF, and regulated by TGFβ signaling, we then hypothesized that MCEMP1 could participate in the transition of circulating monocytes to monocyte-derived alveolar macrophages by controlling cell chemotaxis and/or migration in a TGFβ-rich environment.