Identification and characterization of IgA antibodies against β2-glycoprotein I in childhood Henoch-Schönlein purpura

Summary Background Henoch–Schönlein purpura (HSP) is a common IgA‐mediated vasculitis in children. The antigenic target for IgA is to be determined. Objective To test whether β2‐glycoprotein I (β2GPI) is an antigenic target for IgA in childhood HSP, and to evaluate the clinical implications and pathogenic role of such IgA autoantibodies. Methods The reactivity of patients’ plasma samples and purified polyclonal IgA with β2GPI, β2GPI‐derived peptides and endothelial cells was tested by enzyme‐linked immunosorbent assay. The association between clinical manifestations and IgA anti‐β2GPI antibodies was also analysed. Finally, IgA‐mediated cytotoxicity on endothelial cells was further evaluated. Results At the acute stage, patients with HSP had significantly higher plasma levels of IgA antibodies against β2GPI than healthy controls [reference units (RU) 1·14 ± 0·8 vs. 0·42 ± 0·24, P