Mesenchymal stemcells gain the ability to produce a wide range ofmodulators such as IL-15, TGF-β1, PGE2 andIDO which results in important effects on differenttypes of immune cells such as NK cells (27, 28).Expression of IDO in the tumor microenvironmentnegatively affects the immune response within thetumor through stimulating a regulatory phenotypein CD4+ T cells (29, 30) as well as reduction inthe infiltration of CD3+and CD8+ T-lymphocyteand CD57+ NK cells (31). The gene discussed is IDO1; the disease is neoplasm.