Table 1.

Summary of the role of β2GPI as both a pro- and anticoagulant factor.

Anticoagulant, antiplatelet and profibrinolytic	Evidence derived in vivo/in vitro?	Procoagulant	Evidence derived in vivo/in vitro?
β2GPI can bind the ApoER2’ receptor. ApoER2‘ binds Factor XI on platelets [83] leading to thrombosis. In turn, β2GPI competitively inhibits this mechanism.	In vitro	Various studies have proven that many of the Lupus Anticoagulant (LA) effects seen in APS patients are β2GPI dependent [[84], [85], [86], [87]]. This term lupus anticoagulant is misleading as this effect actually causes increased coagulation in vivo whilst ex vivo the effect is anticoagulant.	In vitro
ApoER2’ on platelets is required for the immobilisation and activation of protein C [88] and thus regulation of thrombin generation. β2GPI also competitively inhibits this process.	In vitro	β2GPI interacts with Annexin V, inhibiting the anticoagulant effect of Annexin V [89].	In vitro
β2GPI can directly inhibit thrombin activation [90].	In vitro	β2GPI demonstrated procoagulant activity by inhibiting activated protein C [91] leading to impaired thrombin generation [92].	In vitro/in vivo
β2GPI prevents plasminogen activator inhibitor 1 from acting upon tissue plasminogen activator, thus downregulating its fibrinolytic activity [90].	In vitro	Activated protein C (aPC) is created by an interaction of thrombomodulin and thrombin at a rate of 1000 fold in comparison to thrombin production alone, β2GPI has been shown to inhibit this interaction, reducing the production of the anticoagulant aPC [93].	In vitro
In the presence of β2GPI, platelet aggregation through ADP is severely impaired [94].	In vitro	β2GPI could inhibit the inhibition of thrombin by a combination of heparin and its cofactor [95].	In vitro
β2GPI binds Factor XI and in turn prevents activation by thrombin thus preventing the formation of a positive feedback loop [32,96].	In vitro
β2GPI interacts with platelets preventing generation of FXa [97].	In vitro