IDO1 and myeloid sarcoma: A study analyzing changes in IDO1 expression and activity in peripheral blood mononuclear cells (PBMC) of relapsing remitting MS patients, showed high IDO1 expression during relapsing phases but not during remission, suggesting activation of Trp catabolism may be associated with disease activity, perhaps representing a self-protective response to control the autoimmune response, similar to the one described in EAE (93).