The antiphospholipid/cofactor syndromes: a primary variant with antibodies to beta 2-glycoprotein-I but no antibodies detectable in standard antiphospholipid assays

Am J Med. 1996 Nov;101(5):472-81. doi: 10.1016/s0002-9343(96)00254-9.

Abstract

Background: Most systemic lupus erythematosus (SLE) patients with two or more clinical manifestations of the antiphospholipid syndrome (APS) and negative antiphospholipid antibodies (aPL) have antibodies to beta 2-glycoprotein-I (a beta 2 GP-I). Herein we describe a similar set of circumstances, but in patients without evidence of SLE.

Patients and methods: We studied 6 patients with recurrent venous and/or arterial thromboses without aPL as detected by routine assays nor clinical or serological evidence of other autoimmune disease. Immunoglobin (Ig) G and IgM antibodies to bovine and human phospholipid-free beta 2 GP-I were studied by Western blot test and by enzyme-linked immunosorbent assay (ELISA) utilizing radiated and nonirradiated plates. We also tested antibodies to cardiolipin, phosphatidylserine, and phosphatidylethanolamine by ELISA. As controls, 54 normal sera were studied.

Results: All 6 patients had recurrent arterial and/or venous thromboses. Three also had thrombocytopenia, 1 had livedo reticularis, and 2 had valvular heart disease. None of the patients had aPL, but all had serum IgG reactivity against human and bovine beta 2 GP-I (P < 0.001 versus controls for both). Titers of anti-bovine beta 2 GP-I were higher when studied in irradiated plates but were also higher than normal in nonirradiated plates (P < 0.001). These antibodies did not recognize human or bovine beta 2 GP-I bound to cardiolipin in solid phase. We confirmed by Western blot that these autoantibodies recognize human beta 2 GP-I. We found no IgM a beta 2 GP-I.

Conclusions: We describe a primary condition akin to the antiphospholipid syndrome with negative aPL, but with serum IgG antibodies to human and bovine beta 2 GP-I. These antibodies recognize beta 2 GP-I epitopes that are not accessible when beta 2 GP-I is bound to cardiolipin.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Autoantibodies / blood*
  • Blotting, Western
  • Cardiolipins / immunology
  • Cattle
  • Enzyme-Linked Immunosorbent Assay
  • Epitopes
  • Factor V
  • Female
  • Genotype
  • Glycoproteins / immunology*
  • Glycoproteins / isolation & purification
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin M / blood
  • Male
  • Middle Aged
  • Mutation
  • Phosphatidylethanolamines / immunology
  • Phosphatidylserines / immunology
  • Protein C
  • Syndrome
  • Thrombosis / immunology*
  • beta 2-Glycoprotein I

Substances

  • Autoantibodies
  • Cardiolipins
  • Epitopes
  • Glycoproteins
  • Immunoglobulin G
  • Immunoglobulin M
  • Phosphatidylethanolamines
  • Phosphatidylserines
  • Protein C
  • beta 2-Glycoprotein I
  • Factor V