THE PRODUCTION, BINDING CHARACTERISTICS AND SEQUENCE-ANALYSIS OF 4 HUMAN-IGG MONOCLONAL ANTIPHOSPHOLIPID ANTIBODIES

Antiphospholid antibodies (APL) have a notable association with recurr ent miscarriages, arterial and venous thrombosis and thrombocytopenia. Analysis of the potential pathogenic effects of such human antibodies has been hampered by the considerable difficulty in producing IgG as opposed to IgM monoclonal immunoglobulins. We have developed four huma n monoclonal IgG APL (LJ1, AH2, DA3 and UK4) by fusing the peripheral blood lymphocytes of three patients with SLE with a mouse:human hetero myeloma cell line, CB-F7. These antibodies bind to a variety of anioni c phospholipids, two (LJ1 and AH2) bind total histones but none binds to ssDNA or dsDNA. Binding to beta 2 GPI is non-specific. UK4 alone de monstrates lupus anticoagulant activity. All four have lambda light ch ains, two are IgG1 (AH2 and UK4) and two are lgG3 (LJ1 and DA3). These APL utilize V-H genes present in the fetally restricted repertoire an d multiple somatic mutations in the CDR suggest an antigen-driven proc ess. In contrast, there is no restriction in V-H gene usage and only o ne lambda chain is extensively mutated. Two clonally related hybridoma s were isolated from a single patient. This supports the theory that c lonal expansion is the mechanism whereby antigen selects high affinity mutations. (C) 1997 Academic Press Limited.