In addition, the present invention also provides for polypeptides comprising the amino acid sequence of residues n-245 of SEQ ID NO:4, where n is an integer in the range of ???17 to 28 and 28 is the position of the first residue from the N-terminus of the complete FcR-II polypeptide (shown in SEQ ID NO:4) believed to be required for receptor binding activity of the FcR-II protein.