The invention generally relates to the field of recombinant protein production.More particularly, the invention relates to the use of avian embryonic derivedstem cell lines, named EBx®, for the production of proteins and more specificallyglycoproteins such as antibodies. The invention is useful for the productionof monoclonal IgG1 antibody subtype having high cell-mediated cytotoxic activity.The invention relates to the use of such antibodies as a drug to treat cancers andinflammatory diseases.