An improved system for large scale production of glycoproteins in cell
culture is provided. In accordance with the present invention, cells
expressing a glycoprotein are grown in media that contain manganese at a
concentration of between approximately 10 and 600 nM. The use of such a
system allows production of a glycoprotein with an increased
glycosylation pattern and/or a glycosylation pattern that more accurately
reflects the glycosylation pattern of the naturally occurring
glycoprotein. A glycoprotein expressed in accordance with the present
invention may be advantageously used in the preparation of pharmaceutical
compositions.