IDO1 and neoplasm: Dying tumor cells may release a series of immunosuppressive molecules, such as cAMP, prostaglandins, indole-2,3-dioxygenase and arginase 1, to mediate immunosuppression,3,4 which also results in the release of inflammatory mediators, such as HMGB1 and HSP70, to promote inflammation.5,6 In addition to the above single molecules, apoptotic tumor cells may release apoptotic bodies, a type of vesicle with sizes ranging from 1 to 5 μm,7 which usually do not induce inflammation.