Recombinant expression vectors are provided comprising a 3′UTR of a light chain and an Epstein-Barr virus origin of replication. Also provided are host cells comprising such vectors and methods of producing recombinant protein with such vectors. Additional methods of producing a recombinant protein involve contacting cells with a first and second vector, each of which encode a different polypeptide chain, and wherein the second vector is present in an amount which is about 1.5 to 2.5 times as much as that of the first vector. Cells also can be transfected with a recombinant transient expression vector encoding a protein and are cultured in a medium in a membrane-enhanced culturing vessel to produce recombinant protein.