In the BALF of IPF patients, a reduced expression of NKG2D on NK, NKT and γδ T cells has been observed which appears to be in response to the elevated expression of TGF-β or stress-induced ligand MHC class I polypeptide-related sequence A (MICA) in those patients (86). Here, MICA is linked to idiopathic pulmonary fibrosis.