When EAE/MS occurs, both the massive secretion of IFN-α/β, IFN- γ, and CTLA-4-CD80/86 between Tregs and DCs can be used as the upstream signal of IDO1 to enhance the expression of IDO1 in DCs, which initiates tryptophan catabolism. The gene discussed is CTLA4; the disease is myeloid sarcoma.