Abstract: The compositions and methods of the present invention are based, in part, on our discovery that an effector function mediated by an Fc-containing polypeptide can be altered by modifying one or more amino acid residues within the polypeptide (by, for example, electrostatic optimization). The polypeptides that can be generated according to the methods of the invention are highly variable, and they can include antibodies and fusion proteins that contain an Fc region or a biologically active portion thereof.

Abstract: The present invention relates to improved methods for producing biologically active truncated APRIL ligand polypeptides and analogs thereof. The invention further relates to truncated APRIL ligand polypeptides and analogs thereof that retain a high biological activity and may be isolated in high yields, as well as the nucleotide sequences that encode the truncated APRIL ligand polypeptides and analogs thereof. The invention also relates to compositions of the biologically active truncated APRIL ligand polypeptides and analogs thereof. The invention further relates to the use of the biologically active truncated APRIL ligand polypeptides and analogs thereof in promoting cell proliferation.