catalytic antibodies and a method for producing the same.

A precursor growth factor comprises a recombinant polypeptide chain wherein said polypeptide chain comprises at least a portion that binds to surface molecules of B cells has a multimerizing inducing element at its C-terminal, at least a portion it binds to surface molecules of T capable of providing dependent T cell help to a B cell, one cleavable antigen by a catalytic antibody and a peptide portion comprising domains cells from such a variable heavy chain and a variable light chain of immunoglobulin and wherein said variable domains heavy chain and variable light chain in the precursor growth factor are associated together by intra- and / or inter-domain bonding binding and prevent substantially the at least one portion which binds to surface molecules B cell surface molecule interacting with a B cell so q ue during segmentacionde said antigen with a catalytic antibody, the peptide comprising said variable domain variable heavy and light chain allow the at least one portion which binds to surface molecules of B cells interacting with a surface molecule of a cell B.