DNA immunization elicits monoclonal antibodies against extracellular epitope of B-lymphocyte antigen CD20. DNA immunization strategy involves the intradermal immunization with naked plasmid DNA encoding the CD20 gene. D4 exhibit potent growth inhibitory activity and have superior direct B-cell cytotoxicity compared to rituximab. We proposed that antibody-induced apoptosis is one of the mechanisms of cell growth inhibition.