TGFB1 and neoplasm: In conjunction with the aforementioned discussion of TGFβ1’s immunosuppressive effects on CTL, these findings indicate that TGFβ1 is capable of compromising both of the major cytolytic mediators associated with anti-tumor immune responses, and its influence on other cells of the immune system ultimately contributes not only to the dysfunction of these cytolytic effector cell populations, but also to the overall promotion of tumor growth and metastasis.