To enable the synthesis of β2-glycoprotein I mutants we have established a stable Chinese hamster ovary cell line that expresses human β2-glycoprotein I up to 2.9 μg/106 cells/day. Recombinant β2-glycoprotein I is identical to the purified native protein with respect to cofactor activity revealed in a modified anti-cardiolipin ELISA. Autoimmune type anti-cardiolipin antibody requires recombinant β2-glycoprotein I in a dose-dependent manner to bind cardiolipin whilst binding of infectious type antibody is inhibited. The purified recombinant β2-glycoprotein I in serum free medium exists as two oligosaccharide species which upon deglycosylation have identical apparent molecular weight to the deglycosylated native protein.
