title: Anti-β2GP1 antibodies have variable effects on platelet aggregation.
abstract: To investigate the effects of affinity-purified rabbit anti-β2GP1, and anti-β2GP1 purified from patients with systemic lupus erythematosus (SLE), on adenosine diphosphate (ADP)-induced aggregation.
  
  
  
  Whole blood was collected and processed to obtain platelet poor plasma (PPP) from normal controls (n = 15) and SLE patients (n = 15). Using PPP, anti-β2GP1 titres were determined using an ELISA and IgG fractions isolated using a HiTrap protein G column. Anti-β2GP1 was purified from two SLE patients using purified β2GP1 coupled to a HiTrap NHS-activated HP column.
  
  
  
  The effect of rabbit and human derived anti-β2GP1 (0-100 μg/mL), on ADP (2.5, 5 μM) induced platelet aggregation were investigated using light transmission aggregometry. Rabbit anti-β2GP1 significantly inhibited all parameters of 5 μM ADP-induced platelet aggregation; %Max (p = 0.028), %AUC (p = 0.014) and slope (p < 0.001). In contrast, anti-β2GP1 purified from SLE patients significantly enhanced the %Max (p = 0.031) and %AUC (p = 0.007) in a concentration dependent manner, but inhibited the slope (p < 0.05) of 5 μM ADP-induced platelet aggregation.
  
  
  
  Our data suggest anti-β2GP1 purified from different species have variable effects on in vitro platelet aggregation. The disparity between rabbit and human anti-β2GP1 may be due to the heterogeneous nature of anti-β2GP1, varying avidity or different antibody binding specificities between species.
authors.affiliation: School of Human Life Sciences, University of Tasmania, Launceston, Tasmania, Australia.
authors.forename: Natasha A
authors.initials: NA
authors.lastname: Betts
authors.forename: Kiran D K
authors.initials: KD
authors.lastname: Ahuja
authors.forename: Murray J
authors.initials: MJ
authors.lastname: Adams
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000818:Animals; D001323:Autoantibodies / Q000276:immunology* / Q000494:pharmacology*; D002846:Chromatography, Affinity / Q000379:methods; D004306:Dose-Response Relationship, Immunologic; D004336:Drug Antagonism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects* / Q000276:immunology*; D011817:Rabbits; D013045:Species Specificity; D053482:beta 2-Glycoprotein I / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D001323:Autoantibodies; D053482:beta 2-Glycoprotein I; D000244:Adenosine Diphosphate