An antibody light chain, comprising as CDRs CDR1L of SEQ ID NO:6, CDR2L of SEQ ID NO:7, and CDR3L of SEQ ID NO:8, is useful as common light chain in a bispecific antibody specifically binding to the extracellular domain of human BCMA and human CD3.Such bispecific antibody can be used as a medicament in the treatment of plasma cell disorders like Multiple Myeloma.