IDO2 and kidney failure: The goal of the present study was to analyze the expression of <i>Ido</i> (indoleamine-2,3-dioxygenase), <i>Kat1</i> (kynurenine aminotransferase 1), <i>Kat2</i> (kynurenine aminotransferase 2), and <i>Kmo</i> (kynurenine-3-monooxygenase) genes in patients undergoing kidney failure with kidney replacement therapy (KFRT) treatment with either hemodiafiltration (HDF) or hemodialysis (HD) in relation to selected clinical and dialysis parameters.