Methods for making modified Fc regions of antibodies and antibody fragments, both human and humanized, and having enhanced stability and efficacy, are provided. Antibodies comprising Fc regions with core fucose residues removed, and attached to oligosaccharides comprising terminal sialyl residues, are provided. Antibodies comprising homogeneous glycosylation of Fc regions with specific oligosaccharides are provided. Fc regions conjugated with homogeneous glycoforms of monosaccharides and trisaccharides, are provided. Methods of preparing human antibodies with modified Fc using glycan engineering, are provided.