Described are novel single-chain multifunctional polypeptides comprising
at least two binding sites specific for the CD19 and CD3 antigen,
respectively. Further provided are polypeptides, wherein the
above-described polypeptide comprises at least one further domain,
preferably of pre-determined function. Furthermore, polynucleotides
encoding said polypeptides as well as to vectors comprising said
polynucleotides and host cells transformed therewith and their use in the
production of said polypeptides are described, In addition, compositions,
preferably pharmaceutical and diagnostic compositions are provided
comprising any of the afore-described polypeptides, polynucleotides or
vectors. Described is also the use of the afore-mentioned polypeptides,
polynucleotides and vectors for the preparation of pharmaceutical
compositions for immunotherapy, preferably against B-cell malignancies
such as non-Hodgkin lymphoma.