Heterogeneity of anti-β2-glycoprotein I antibodies

Summary

The aim of this study was to evaluate the heterogeneity of IgG-anti- β₂ -glycoprotein I antibodies (IgG-aβ₂ GPI) as regarding their reactivity pattern against different sources of human β₂ GPI,their avidity and their association with clinical events of antiphospholipid syndrome (APS).Three thousand six hundred and eightyfour consecutive patient sera were routinely tested for IgG-a β₂ GPI over 1 year using an in-house ELISA with 2 different commercial preparations of human purified β₂GPI. Of the 340 sera found positive, all those clinically documented were included in this study; 61 were positive with only one preparation (S1) and 59 with both (S2).The results of ELISA were confirmed by Western blot. Heterogeneity was stressed by testing sera with a human recombinant protein and 3 β₂ GPI-related peptides. No contribution of glycosylation in the binding to β₂GPI was found.The avidity indices for each protein were significantly higher in S1 than in S2 (p = 0.0021). S2 were more associated with antiphospholipid antibodies than S1 (75% versus 21% ; p <0.0001).A similar frequency of the main clinical features of APS was found in S1 and S2 sera (69% and 71%, respectively). In conclusion, our data show a heterogeneity in the antigenic reactivity pattern of IgG- a β₂ GPI and a relationship between a binding profile and antibody avidity.This heterogeneity could represent a crucial factor of variability in test results and underlines the difficulty of getting standardisation.

Keywords

β2-glycoprotein I - heterogeneity - avidity - antiphospholipid syndrome

 

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