Expression of human recombinant beta 2-glycoprotein I with anticardiolipin antibody cofactor activity.

To enable the synthesis of beta 2-glycoprotein I mutants we have established a stable Chinese hamster ovary cell line that expresses human beta 2-glycoprotein I up to 2.9 micrograms/10(6) cells/day. Recombinant beta 2-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 beta 2-glycoprotein I in a dose-dependent manner to bind cardiolipin whilst binding of infectious type antibody is inhibited. The purified recombinant beta 2-glycoprotein I in serum free medium exists as two oligosaccharide species which upon deglycosylation have identical apparent molecular weight to the deglycosylated native protein.