Type 1 invariant natural killer T cells drive lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease characterised by excessive extracellular matrix deposition in the lung parenchyma. There is a critical need to understand the mechanisms involved in IPF to develop new treatments. Natural Killer T (NKT) cells are a group of innate-like T cells which express NK cell receptors and antigen T cell receptors (TCR). The role of NKT cells in IPF is not understood. We analysed bronchoalveolar lavage (BAL) fluid from IPF patients and healthy controls, by quantitative PCR and by flow cytometry. IPF patients had increased expression in whole BAL pellets of pro-fibrotic factors as Collagen 1-a1, osteopontin and TGF-b, as assessed by qPCR. Flow cytometry analysis indicated that there were distinct populations of CD45+CD3+CD56+ (NKT cells) in IPF BAL. We detected an increase in IFN-g producing NKT cells in IPF, compared to controls. We confirmed NKT cell phenotype in a second cohort, using an antibody against Vα24-Jα18 of the iNKT TCR. BAL iNKT cells had increased expression of CXCR5, CXCR6, CXCR3 and CD244, as well as CD244+CXCR6+ iNKT cells compared to blood. Next, we utilized the murine bleomycin model of pulmonary fibrosis. Wild-type (WT) C57BL/6 mice were instilled with a single dose of bleomycin (1.5 IU/Kg via the intratracheal route), with or without daily administration of GRI-0621, a small molecule selective inhibitor of iNKT activity, nintedanib, or control, via oral gavage. Compared to controls, GRI-0621 treated mice had improved fibrosis, pathology and reduced lung TGF-b. Collectively, these data suggest that NKT cells are activated in airways in IPF patients and inhibition of iNKT cell activity can ameliorate bleomycin-induced pulmonary fibrosis.