The fact that IL-6 and IL-15 are inhibitor and activator, respectively, of NK effector functions [25, 26], together with the enhanced IFN-γ release by TdLN cells from tumor-bearing shCD5EμTg mice under both specific and non-specific re-stimulation conditions, prompted us to confirm a putative implication of NK cells in the anti-tumor effects induced by transgenic or exogenous shCD5. This evidence concerns the gene IL15 and neoplasm.