IDO1 and melanoma: Proposed mechanisms for melanoma-derived immunosuppression include the secretion of TGFβ, IL-10 and IDO, which have been found in patients' blood, primary melanomas and sentinel lymph nodes (SLN) (Reed et al, 1994; Real et al, 2001; Lee et al, 2003, 2005; Redondo et al, 2003).