Thus, depletion by indoleamine-2,3-dioxygenase (IDO) expressed either in tumour cells or antigen-presenting cells, as well as the production of an end product like kynurenine, has been related to immunosuppression in the cancer cellular microenvironment and in lymph nodes draining it, thus inducing T-cell anergy and apoptosis facilitating cancer expansion [47]. The gene discussed is IDO1; the disease is cancer.