Indoleamine 2,3 Dioxygenase (IDO) Expression and Activity in Relapsing-Remitting MS

BACKGROUND: Interferon gamma (IFN-\u3b3) production induces the transcription of indoleamine 2,3 dioxygenase (IDO) resulting in the reduction of T-cell activation and proliferation through the depletion of tryptophan and the elicitation of Treg lymphocytes. IDO was shown to be involved in the pathogenesis of autoimmune diseases; we investigated whether changes in IDO gene expression and activity could be indicative of onset of relapse in multiple sclerosis (MS) patients. METHODS: IDO and interferon-\u3b3 (IFN-\u3b3) gene expression, serum IDO activity (Kynurenine/Tryptophan ratio) and serum neopterin concentration--a protein released by macrophages upon IFN-\u3b3 stimulation--were measured in 51 individuals: 36 relapsing remitting (RR)-MS patients (21 in acute phase--AMS, 15 in stable phase--SMS) and 15 healthy controls (HC). PBMCs samples in AMS patients were collected before (BT-AMS) and during glucocorticoids-based therapy (DT-AMS). RESULTS: IDO expression was increased and IFN-\u3b3 was decreased (p<0.001) in BT-AMS compared to SMS patients. Glucocorticoids-induced disease remission resulted in a significant reduction of IDO and IFN-\u3b3 gene expression, IDO catalytic activity (p