Abstract: A fusion protein composition of an antibody Fc region which is useful as a medicament in which effector function is improved is desired. The present invention provides a fusion protein composition comprising a fusion protein molecule of an antibody Fc region having complex type N-glycoside-linked sugar chains in the Fc region, wherein the complex type N-glycoside-linked sugar chains have a structure in which fucose is not bound to N-acetylglucosamine in the reducing end in the sugar chains; a transformant producing the fusion protein composition; a process for producing the fusion protein composition; and a medicament comprising the fusion protein composition.

Abstract: Development of a host cell capable of producing a glycoprotein composition such as an antibody composition which is useful in development of medicaments is desired. The present invention provides a cell in which a genomic gene encoding an enzyme relating to a sugar chain modification in which 1-position of fucose is bound to 6-position of N-acetylglucosamine in the reducing end through ?-bond in a complex type N-glycoside-linked sugar chain is knocked out, wherein the cell is naturalized in a serum-free medium and a process for producing a glycoprotein composition using the cell.