title: Prevalence of antibodies to cardiolipin in chronic ITP and reactivity with platelet membranes.
abstract: Anti-cardiolipin antibodies (ACLA) have been suggested to play a role in the pathogenesis of thrombocytopenia. When sera from 40 patients with chronic idiopathic thrombocytopenic purpura (ITP) were analyzed for ACLA, these autoantibodies were present in 12 (30%). In 4 sera the antibody activity was restricted to the IgG or IgM isotype, respectively, while 4 of the samples contained both IgG and IgM antibodies. To elucidate the interaction between platelets and ACLA, we studied the reactivity of sera from non-ITP patients with ACLA, with fragmented platelet membranes. None of them had a concurrent platelet deficiency, but sera from 8 (67%) of them showed increased IgG-binding to platelet membranes. Absorbtion with cardiolipin reduced membrane binding in 6 (50%). C3 levels were normal, while low C4 values occurred in both groups with significantly lower levels in ACLA-positive patients (p<0.05). Circulating immune complexes (CIC) were common in both groups.
  
  
  CONCLUSIONS
  The prevalence of ACLA is increased in ITP and sera from non-ITP patients with ACLA react with fragmented platelet membranes. This reactivity is often decreased by absorption with cardiolipin, suggesting that ACLA bind to phospholipid epitopes on platelet membranes.
authors.affiliation: Department of Medicine, Karolinska Hospital, Stockholm, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Arfors
authors.forename: J
authors.initials: J
authors.lastname: Winiarski
authors.forename: A K
authors.initials: AK
authors.lastname: Lefvert
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017153:Antibodies, Anticardiolipin / Q000097:blood / Q000276:immunology*; D000936:Antigen-Antibody Complex / Q000097:blood*; D016824:Antigens, Human Platelet / Q000276:immunology*; D001327:Autoimmune Diseases / Q000097:blood / Q000276:immunology*; D002308:Cardiolipins / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D003429:Cross Reactions; D005260:Female; D006801:Humans; D008081:Liposomes; D008297:Male; D008875:Middle Aged; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D015995:Prevalence; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood / Q000276:immunology*
chemical_list: D017153:Antibodies, Anticardiolipin; D000936:Antigen-Antibody Complex; D016824:Antigens, Human Platelet; D002308:Cardiolipins; D003176:Complement C3; D003181:Complement C4; D008081:Liposomes; D010980:Platelet Membrane Glycoproteins