Immunotherapeutic approaches involving genetic modification of T cells show promise in generating highly specific tumor-reactive effector cells for cancer treatment. Given the high affinity of FcRI (the subtype I Fc receptor for IgE) for IgE monoclonal antibody (mAb), modification of T cells with chimeric FcRI in combination with tumor-specific IgE mAbs is potentially a powerful and effective strategy to specifically target T cells to tumor cells. In this study, we retrovirally transduce human primary T cells with a cDNA encoding the extracellular domain of FcRI linked to the hinge and transmembrane domains of FcRI and the cytoplasmic domains of CD28 and T cell receptor zeta chain (FcRI-CD28-zeta). We demonstrate that human T cells expressing FcRI-CD28-zeta, in the presence of tumor-specific IgE mAb recognizing mouse CD8 antigen (Ly- 2.1+), can specifically secrete cytokine, proliferate, and mediate cytotoxic function after antigen ligation. Furthermore, adoptive transfer of FcRI-CD28-zeta cells incubated with anti-Ly-2.1 IgE mAb significantly enhances the survival of irradiated nonobese diabetic-severe combined immunodeficiency mice bearing Ly-2.1+ tumor compared with control mice. Thus, this set of experiments demonstrates that Fc gene-engineered human T cells mediate effector function in vitro and in vivo in an IgE-dependent manner and thus a novel and valid approach for cancer therapy can now be further developed.