Other studies have indicated that decreased production of AhR ligands such as microbiota-derived indoles and Trp derivatives can induct allogeneic T cell reactivity after allogeneic hematopoietic stem cell transplantation (HSCT) (45) and that plasma amino acids (including Trp) from HSCT patients are reduced in those experiencing sinosoidal obstruction syndrome and Graft-versus-Host Disease (GvHD) (46). Here, AHR is linked to graft versus host disease.