Characterization of a recombinant proteinase 3, the autoantigen in Wegener's granulomatosis and its reactivity with anti-neutrophil cytoplasmic autoantibodies.

Using the baculovirus/insect cells system, we have expressed a recombinant proteinase 3 (PR3) -- the neutrophil-derived serine protease autoantigen in Wegener's granulomatosis -- as a glycosylated intracellular and membrane-associated protein. Oligosaccharides accounted for the difference in molecular weights between recombinant (34 kDa) and neutrophil-PR3 (29 kDa). Whereas rabbit-anti-PR3 IgG recognized both recombinant and neutrophil-derived PR3, autoantibodies from Wegener patient sera recognized only neutrophil-derived PR3. Although oligosaccharides were not involved in PR3 epitope recognition, autoantibodies did not recognize the amino acid primary structure of recombinant PR3. Improper disulfide bond formation and/or lack of post-translational events in insect cells, may affect the conformation and/or lack of post-translational events in insect cells, may affect the conformation of PR3, precluding its reactivity with sera from WG patients.