Abstract: Compositions and methods for minimizing antibody disulfide bond reduction are described. In one aspect, a composition is provided for culturing mammalian host cells to express an antibody including an anti-reduction agent that minimizes reduction of a disulfide bond in the antibody or fragment thereof. In some other aspects, methods for minimizing disulfide bond reduction; increasing production of an antibody or fragment thereof with intact native disulfide bonds; increasing a ratio of non-reduced to reduced antibody or fragment thereof; producing a therapeutic antibody or fragment thereof by adding a sufficient amount of an anti-reduction agent to a cell culture media, pre-harvest cell culture fluid, or harvest cell culture fluid are described. In another aspect, minimizing disulfide bond reduction in an antibody or fragment thereof culturing the host cell in a concentration of at least about 20% O2 is described.