Cross-reactivity of IgM and IgG anticardiolipin antibodies with oxidized-low density lipoproteins

Anticardiolipin antibodies (aCLAs) and antibodies to oxidized-low density lipoproteins (oxLDL) are associated with two distinct diseases: the antiphospholipid syndrome and atherosclerosis. Because both diseases may be apparent in patients with systemic lupus erythematosus (SLE), it is important to establish the relationship between these two types of antibodies. In the present study, we examined whether sera containing IgM and/or IgG aCLAs also react with LDL that has been oxidized by conjugation with malondialdehyde (MDA-LDL) or by incubation with copper ions (Cu-LDL). Results revealed a clear correlation between IgM aCLAs and IgM anti-MDA-LDL antibodies, and a weak correlation between IgG aCLAs and IgG anti-Cu-LDL antibodies. Cross-reactivity between both antibodies seemed to be limited. Because aCLAs are heterogeneous, only a minor subset of these antibodies may cross-react with oxLDL. Therefore, identification of both antibodies may be relevant for determination of the prognosis of accelerated atherosclerosis in SLE patients.