Compared with the CDC of rituximab, IgG-scFv-CD55 × CD20 showed 0.72- and 0.75-fold CDC in BJAB and Ramos-RR cells, respectively, indicating decreased tumor cell killing activity; scFv-bsAb showed 1.27- and 1.15-fold CDC in BJAB and Ramos-RR cells, respectively, indicating similar or slightly enhanced CDC. This evidence concerns the gene CD55 and neoplasm.