Currently the highly successful technology is termed ‘BiTEs’ (bi-specific T cell engagers) and Blinatumomab (MT103; Micromet/Medimmune), a BiTE specific for CD19 and CD3, is used to treat patients with non-Hodgkin's lymphoma and is also in several clinical trials for the treatment of acute lymphoblastic leukemia (ALL) [8]. Here, CD19 is linked to acute lymphoblastic leukemia.