The present invention relates generally to genetically modified non-human animals and immunodeficient non-human animals characterized by restored complement-dependent cytotoxicity, as well as methods and compositions for assessment of therapeutic antibodies in the genetically modified immunodeficient non-human animals. In specific aspects, the present invention relates to immunodeficient non-obese diabetic (NOD), A/J, A/He, AKR, DBA/2, NZB/BIN, B10.D2/oSn and other mouse strains genetically modified to restore complement-dependent cytotoxicity which is lacking in the unmodified immunodeficient mice. In further specific aspects, the present invention relates to NOD.Cg-Prkdcscid IL2rgtm1Wjl/SzJ (NSG), NOD.Cg-Rag1tm1Mom IL2rgtm1Wjl/SzJ (NRG) and NOD.Cg-Prkdcscid IL2rgtm1Sug/JicTAc (NOG) mice genetically modified to restore complement-dependent cytotoxicity which is lacking in unmodified NSG, NRG and NOG mice. Methods for assessment of therapeutic antibodies or putative therapeutic antibodies in the genetically modified immunodeficient mice characterized by an intact complement system are provided according to specific aspects of the present invention.