AIM To study the expression of brain-derived neurotrophic factor (BDNF) in lymphocytes modified by BDNF gene and its effect on the proliferation and the H 2O 2-induced apoptosis of PC12 cells for the transfer of ex vivo therapeutic gene into central nervous system (CNS) tissue with atraumatic means. METHODS Recombined BDNF cDNA plasmid was transfected by LipofectAMINE into the packing cell line PA317 and G418-resistant clones with highest titer was selected. Rat lymphocytes were infected repeatedly with virus supernatant. The expression of BDNF in rat lymphocytes was assayed by FCM and immunohistochemistry. The proliferation of PC12 cells was evaluated by MTT assay. H 2O 2-induced apoptosis of PC12 cells was determined by PI stain flow cytometry. RESULTS BDNF expressed in rat lymphocytes genetically modified and the concentration of BDNF in the conditioned medium of engineered lymphocytes had a linear correlation with the proliferation of the PC12 cells. The supernatant of lymphocytes modified by BDNF gene decreased the apoptosis of PC12 cells induced by H 2O 2. CONCLUSION Rat lymphocytes genetically modified can express and secret active BDNF in vitro.