Paywall, https://www.sciencedirect.com/science/article/pii/S0531556519305807 Sci hub, https://sci-hub.se/10.1016/j.exger.2019.110820
>'The initial enzyme, indoleamine 2,3-dioxygenase (IDO1) is induced by IFNγ, while tryptophan-2,3-dioxygenase (TDO) is induced by corticosteroids.' That's interesting. My ME symptoms were worse during periods when my IFN-g should have been elevated (24 hrs after physical exertion, or viral infections), and were definitely made worse by elevating TRP in my brain. Prednisone gave me temporary remission the first two times (then stopped working). Maybe the prednisone boosted TDO enough to temporarily deplete TRP in my brain, making it unavailable to the IDO pathway, which leads to neurotoxic kynurenines. Not sure how to test that now.