This observation raises the possibility, that the KP has a complex role in the pathomechanism of MS, it behaves differently in short and long term, and it responds differently in immune-mediated and non immune-mediated conditions, as MS is an immune-mediated disease of CNS, in which the KP, including the IDO enzyme, is greatly affected by the immune pathways (Vécsei et al., 2013). Here, IDO1 is linked to myeloid sarcoma.