The clinical benefit of adoptive transfer of MHC-restricted cytotoxic T lymphocytes(CTL) for the treatment of cancer is hampered by the low success rate to generate antitumor CTLs. To bypass the need for tumor-specific CTL, we developed a strategy that allows for grafting of human T lymphocytes with MHC-restricted antigen specificity using in vitro selected human Fab fragments fused to the Fc(epsilon)RI-gamma signaling molecule. Retroviral introduction of a Fab-based chimeric receptor specific for MAGE-A1/HLA-A1 into primary human T lymphocytes resulted in binding of relevant peptide/MHC complexes. Transduced T lymphocytes responded to native MAGE-A1/HLA-A1POS target cells by specific cytokine production and cytolysis. Therefore, peptide/MHC-specific Fab fragments represent new alternatives to TCR to confer human T lymphocytes with tumor specificity, which provides a promising rationale for developing immunogene therapies.