The present invention includes a diabody molecules, immune disorders, infectious diseases, addiction relates to the use of the molecule in the treatment of a variety of diseases and disorders such as cancer. Diabody molecules of the present invention are those containing two polypeptide chains attached to form at least two epitope binding sites (capable of recognizing the same or different epitopes on the same or different antigens). Furthermore, the antigen may be derived from the same molecule, it may be derived from different molecules. Individual polypeptide chains of the diabody molecules is covalently linked via a non-peptide bonds form covalent bonds, for example, but are covalently linked by disulfide bonds of the cysteine ​​residues present in each polypeptide chain, which but it is not limited to. In certain embodiments, diabody molecules of the present invention further comprise an Fc region to have antibody-like functionality to the molecule.