IDO1 and B-cell chronic lymphocytic leukemia: Collectively, these findings appear intriguing, in the context of the experimental observations here described: the number of MDSCs is, in fact, significantly high in CLL patients and correlates with unfavorable prognostic markers, shorter survival times and overexpression of IDO, ARG1, NOS2, IL-10 and TGFβ [41,51,52].