AXL and idiopathic pulmonary fibrosis: Mer was found to be upregulated in a sub-population of IPF macrophages, possibly being involved in the activation of IPF myofibroblasts and lung fibrosis [72]; on the other hand, Axl was associated with loss of alveolar epithelium integrity and it was identified as a negative regulator of an alveolar epithelial phenotype [73].