Recent studies have shown that the IL‐33/ST2 pathway plays an important role in inflammation and fibrosis in various organs such as heart,14 lung,15 gastrointestinal tract 16 and liver 17; moreover, sST2 is a useful biomarker for predicting clinical outcome in graft‐vs‐host disease (GVHD),18, 19 myocardial infarction 20 and heart failure 21 and kidney disorders such as IgA nephropathy,22 lupus nephritis 23 and chronic kidney disease.24, 25, 26 However, the role of ST2 in PF has not been previously reported. The gene discussed is IL33; the disease is graft versus host disease.