CD19xCD3 BiTE (top), CD19xCD3 DART (middle), and CD19xTCR DART (bottom) cross-link a normal or malignant B cell through CD19 (left) and a T cell through the TCR complex (right). BiTEs consist of a single polypeptide displaying 2 antigen-binding specificities through cognate heavy (gray) and light chain (white) variable domains (shown with the 3 complementarity determining regions). BiTEs have 1 N-terminus (N, shown in blue) and 1 C-terminus (C, shown in red). In DARTs, cognate heavy and light chain variable domains are on 2 separate polypeptides that associate and are stabilized by a C-terminal disulfide bridge. Thus, DARTs have 2 N-termini and 2 C-termini.