Certain embodiments are directed to a bispecific immunoglobulin that is capable of binding cell surface molecules on a target cell, such as cancer cells, and cell surface molecules on immune effector cell, such as cytotoxic T lymphocytes, resulting in the targeted killing of target cells. In certain aspects a Bif is a polypeptide comprising a first target binding domain that specifically binds a cancer cell, a second effector binding domain that specifically binds an immunologic effector, and an immunoglobulin constant region linker operatively coupling the first and second binding domain.