The invention features proteins including an antibody, or functional derivatives thereof, that bind hCD59 and have the activity of domain 4 of the Streptococcus intermedins intermedilysin (ILY) protein. In order to prevent the independent induction of CDC and ADCC, the antibodies of the invention can bind the same hCD59 epitope as ILYd4 and/or contain modifications that disrupt the interaction between the antibody and complement.