The human IgG4 monoclonal antibody was produced as a recombinant protein in mycoplasma free CHO cells under serum-free conditions. This antibody reacts against a hapten that is not expressed in mammalian cells. It can be used as an isotype control when evaluating fully human, humanized, or chimeric antibodies. The human IgG4 monoclonal antibody is suitable as an isotype-matched control for ELISA, immunoblotting, FACS, IHC, and functional studies.