Anti-β2-glycoprotein I antibodies in children with atopic dermatitis

Abstract

β2-Glycoprotein I (β2GPI) appears to be the major antigen for antiphospholipid antibodies (aPL) in patients with antiphospholipid syndrome (APS). In early infancy, virtually all children initiate transient immune response to non-pathogenic nutritional antigens, which fails to terminate in children with atopic diseases. To examine the possibility that a prolonged immune response to β2GPI could also spread to the human protein, antibodies against human β2GPI (anti-β2GPI) were determined in 93 randomly selected children with different allergic diseases. A high frequency (42%) of IgG anti-β2GPI was found in children with atopic dermatitis (AD), but not in those with other allergic diseases. Anti-β2GPI in children with AD were exclusively of the IgG1 subclass and bound to bovine β2GPI as well, but not to either β2GPI combined with the phospholipid cardiolipin. The epitopes were identified in domain V of β2GPI and the antibody binding was abolished upon the specific proteolytic cleavage of the phospholipid-binding C-terminal loop in domain V of β2GPI. These results indicated that the epitopes for anti-β2GPI in children with AD most likely resided in close vicinity of the phospholipid-binding site of β2GPI. The epitopic difference from anti-β2GPI in APS may explain presumed non-thrombogenicity of anti-β2GPI in children with AD.