Interestingly, TGF-β is a well-characterized factor promoting establishment of tissue-resident memory T cells with cytotoxic functions in human skin.47 Therefore, while our data generally suggest an anti-inflammatory role of MΦs in previously untreated aGvHD, changes in the skin environment could lead to rapid repolarization in the later stages of disease, including steroid-refractory GvHD. This evidence concerns the gene TGFB1 and graft versus host disease.