Which antibody form is involved in antiphospholipid syndrome and linked to fetal loss and thrombosis?

• A. IgG, IgM, IgA
• B. IgG, IgA, IgM
• C. IgM, IgA, IgG
• D. IgG, IgM, IgD

Answer: (A)

Antiphospholipid syndrome involves antibodies against phospholipid-binding proteins that can belong to any of the main immunoglobulin classes: IgG, IgM, or IgA. These antiphospholipid antibodies—such as anticardiolipin and anti–beta2 glycoprotein I—are linked to pregnancy loss and thrombosis because they promote a prothrombotic state by activating endothelial cells and platelets, disrupting anticoagulant pathways, and altering the surface protection provided by annexin A5. Among the isotypes, IgG is the one most strongly associated with adverse pregnancy outcomes and clotting, but IgM and IgA can also be present in APS. Therefore, the antibody forms involved are IgG, IgM, and IgA.