Isolation and characterization of two human monoclonal anti-phospholipid IgG from patients with autoimmune disease

J Autoimmun. 1999 Sep;13(2):215-23. doi: 10.1006/jaut.1999.0316.


The antigenic specificity of anti-phospholipid antibodies (APA) is a matter of intensive investigation. To further characterize these antibodies, we attempted to isolate human monoclonal APA. B-cells of patients with at least one positive test for antibodies against cardiolipin, phosphatidylserine, beta2-glycoprotein I (beta2-GPI) or the lupus anti-coagulant were immortalized by transformation with Epstein-Barr virus and screened for production of specific IgG. Positive pools were fused with a heteromyeloma cell line and APA-secreting clones were isolated by standard procedures. Two monoclonal APA, HL-5B from a 51-year-old man with primary anti-phospholipid syndrome and recurrent cerebral microinfarctions, and RR-7F from a 48-year-old women with systemic lupus erythematosus but no evidence for thrombotic events were obtained. HL-5B is of the IgG2 subtype with lambda light chains, while RR-7F is IgG2 with kappa light chains. Both monoclonals show reactivity against cardiolipin and phosphatidylserine but lack reactivity against beta2-GPI or lupus anti-coagulant activity. To yield the same OD in the cardiolipin and phosphatidylserine ELISAs RR-7F must be used in an approximately 10-fold higher concentration than HL-5B, indicating a lower affinity towards these antigens. Interestingly, both mAPA can bind to cardiolipin in the absence of beta2-GPI. They do not cross-react with dsDNA but show reactivity against oxidized low-density lipoproteins. Analysis of the heavy chain mRNA of HL-5B and RR-7F showed that both are members of the VH3 family. While HL-5B shows extensive somatic mutations in the CDR1 and 2 regions, indicating that it was derived by a T cell-dependent antigen driven process, RR-7F is apparently germline encoded. The two monoclonal APA can be used as tools in further structural and functional analyses.

Publication types

  • Case Reports

MeSH terms

  • Amino Acid Sequence
  • Antibodies, Monoclonal / immunology*
  • Antibody Specificity
  • Antiphospholipid Syndrome / immunology*
  • Autoantibodies / immunology*
  • Base Sequence
  • Cardiolipins / immunology
  • Female
  • Glycoproteins / immunology
  • Humans
  • Immunoglobulin G / genetics
  • Immunoglobulin G / immunology*
  • Immunoglobulin Heavy Chains / genetics
  • Immunoglobulin Variable Region / genetics
  • Lupus Coagulation Inhibitor / analysis
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Phosphatidylserines / immunology
  • Phospholipids / immunology
  • beta 2-Glycoprotein I


  • Antibodies, Monoclonal
  • Autoantibodies
  • Cardiolipins
  • Glycoproteins
  • Immunoglobulin G
  • Immunoglobulin Heavy Chains
  • Immunoglobulin Variable Region
  • Lupus Coagulation Inhibitor
  • Phosphatidylserines
  • Phospholipids
  • beta 2-Glycoprotein I