To assess whether the observed anti-CD19(Fab)-LDM-mediated inhibition of cell growth of MDR cells in vitro would extend to animal models, we established BJAB and BJAB/ADR xenograft tumor mouse models to investigate the MDR phenomenon in vivo to investigate the therapeutic effect of anti-CD19(Fab)-LDM on the BJAB/ADR xenograft model. The gene discussed is CD19; the disease is neoplasm.