Abstract: The present invention relates to novel multi-functional polypeptides comprising at least two antigen binding sites specific for the CD11b and CD15 cell surface markers. The present invention further relates to a polypeptide, wherein the above-described polypeptide comprises at least one further domain, preferably of pre-determined function. Furthermore, the present invention relates to polynucleotides encoding said polypeptides as well as to vectors comprising said polynucleotides and to host cells transformed therewith and their use in the production of said polypeptides. In addition, the present invention relates to compositions, preferably pharmaceutical and diagnostic compositions, comprising any of the afore-described polypeptides, polynucleotides or vectors as well as to kits comprising said compositions. A further object of the present invention is the use of said compositions for therapeutic, diagnostic and cell separation methods.