Among antiphospholipid antibodies, which is considered more pathogenic?

Among antiphospholipid antibodies, which is considered more pathogenic?

• A. APL IgG
• B. LAC
• C. APL IgM
• D. APL IgA

Answer: (B)

Lupus anticoagulant is considered the most pathogenic among antiphospholipid antibodies because its presence carries the strongest association with thrombotic events, both arterial and venous, compared with anticardiolipin and anti‑β2 glycoprotein I antibodies. In the lab, lupus anticoagulant prolongs phospholipid-dependent clotting tests (such as dilute Russell viper venom time) by interfering with the formation of coagulation complexes that need phospholipid surfaces. Paradoxically, this in vitro prolongation reflects a prothrombotic tendency in vivo, as these antibodies promote thrombin generation, platelet activation, endothelial activation, and disruption of natural anticoagulant mechanisms. While anticardiolipin antibodies and anti‑β2 glycoprotein I antibodies also increase thrombosis risk, their association is generally weaker than that of lupus anticoagulant. IgA antibodies have a more variable and less well-established role and are not as strongly linked to thrombosis as lupus anticoagulant.

Lupus anticoagulant is considered the most pathogenic among antiphospholipid antibodies because its presence carries the strongest association with thrombotic events, both arterial and venous, compared with anticardiolipin and anti‑β2 glycoprotein I antibodies. In the lab, lupus anticoagulant prolongs phospholipid-dependent clotting tests (such as dilute Russell viper venom time) by interfering with the formation of coagulation complexes that need phospholipid surfaces. Paradoxically, this in vitro prolongation reflects a prothrombotic tendency in vivo, as these antibodies promote thrombin generation, platelet activation, endothelial activation, and disruption of natural anticoagulant mechanisms. While anticardiolipin antibodies and anti‑β2 glycoprotein I antibodies also increase thrombosis risk, their association is generally weaker than that of lupus anticoagulant. IgA antibodies have a more variable and less well-established role and are not as strongly linked to thrombosis as lupus anticoagulant.